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ITEM 1A. RISK FACTORS

Investors should review carefully the following material risk factors and the other information contained in this report. The risks that the Ameren Companies face are not limited to those in this section. There may be further risks and uncertainties that are not presently known or that are not currently believed to be material that may adversely affect the results of operations, financial position, and liquidity of the Ameren Companies.

REGULATORY AND LEGISLATIVE RISKS

We are subject to extensive regulation of our businesses.

We are subject to federal, state, and local regulation. The extensive regulatory frameworks, some of which are more specifically identified in the following risk factors, regulate, among other matters, the electric and natural gas utility industries; the rate and cost structure of utilities, including an allowed ROE; the operation of nuclear power plants; the construction and operation of generation, transmission, and distribution facilities; the acquisition, disposal, depreciation and amortization of assets and facilities; the electric transmission system reliability; and wholesale and retail competition. In the planning and management of our operations, we must address the effects of existing and proposed laws and regulations and potential changes in our regulatory frameworks, including initiatives by federal and state legislatures, RTOs, utility regulators, and taxing authorities. Significant changes in the nature of the regulation of our businesses, including expiration of, or significant changes to, existing regulatory mechanisms, could require changes to our business planning and management of our businesses and could adversely affect our results of operations, financial position, and liquidity. Failure to obtain adequate rates or regulatory approvals in a timely manner; failure to obtain necessary licenses or permits from regulatory authorities; the impact of new or modified laws, regulations, standards, interpretations, or other legal requirements; or increased compliance costs could adversely affect our results of operations, financial position, and liquidity.

The electric and natural gas rates that we are allowed to charge are determined through regulatory proceedings, which are subject to intervention and appeal. Rates are also subject to legislative actions, which are largely outside of our control. Certain events could prevent us from recovering our costs in a timely manner or from earning adequate returns on our investments.

The rates that we are allowed to charge for our utility services significantly influence our results of operations, financial position, and liquidity. The electric and natural gas utility industry is highly regulated. The utility rates charged to customers are determined by governmental entities, including the MoPSC, the ICC, and the FERC. Decisions by these entities are influenced by many factors, including the cost of providing service, the prudency of expenditures, the quality of service, regulatory staff knowledge and experience, customer intervention, and economic conditions, as well as social and political views. Decisions made by these governmental entities regarding customer rates are largely outside of our control. We are exposed to regulatory lag and cost disallowances to varying degrees by jurisdiction, which, if unmitigated, could adversely affect our results of operations, financial position, and liquidity. Rate orders are also subject to appeal, which creates additional uncertainty as to the rates that we will ultimately be allowed to charge for our services. From time to time, our regulators may approve trackers, riders, or other recovery mechanisms that allow electric or natural gas rates to be adjusted without a traditional regulatory rate review. These mechanisms could be changed or terminated.

Ameren Missouri’s electric and natural gas utility rates and Ameren Illinois’ natural gas utility rates are typically established in regulatory proceedings that take up to 11 months to complete. Ameren Missouri’s rates established in those proceedings are primarily based on historical costs and revenues. Ameren Illinois’ natural gas rates established in those proceedings are based on estimated future costs and revenues. Thus, the rates that we are allowed to charge for utility services may not match our actual costs at any given time.

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Rates include an allowed return on investments established by the regulator, including a return at the applicable WACC on rate base, and an amount for income taxes based on the currently applicable statutory income tax rates and amortization associated with excess deferred income taxes. Although rate regulation is premised on providing an opportunity to earn a reasonable rate of return on rate base, there can be no assurance that the regulator will determine that our costs were prudently incurred or that the regulatory process will result in rates that will produce full recovery of such costs or provide for an opportunity to earn a reasonable return on those investments. Ameren Missouri and Ameren Illinois, and the utility industry generally, have an increased need for cost recovery, primarily driven by capital investments, which is likely to continue in the future. The resulting increase to the revenue requirement needed to recover such costs and earn a return on investments could result in more frequent regulatory rate reviews and requests for cost recovery mechanisms. Additionally, increasing rates could result in regulatory or legislative actions, as well as competitive or political pressures, all of which could adversely affect our results of operations, financial position, and liquidity.

As a result of its participation in performance-based formula ratemaking, Ameren Illinois’ ROE for its electric distribution service and its electric energy-efficiency investments is directly correlated to yields on United States Treasury bonds. Additionally, Ameren Illinois is required to achieve certain performance standards. With respect to its natural gas delivery service business, unless extended, Ameren Illinois’ QIP will sunset after December 2023.

Ameren Illinois elects to participate in a performance-based formula ratemaking framework established pursuant to the IEIMA for its electric distribution service. Ameren Illinois’ electric distribution revenues are decoupled from sales volumes, which ensures that the electric distribution revenues authorized in a regulatory rate review are not affected by changes in sales volumes. Ameren Illinois also has an electric energy-efficiency program rider, which includes a return at the applicable WACC on its program investments that is subject to performance-based formula ratemaking. The ICC annually reviews Ameren Illinois’ rate filings for reasonableness and prudency. If the ICC were to conclude that Ameren Illinois’ costs were not prudently incurred, the ICC would disallow recovery of such costs. The electric distribution service performance-based formula ratemaking framework expires at the end of 2022, if not extended by the legislature, while the decoupling provisions extend beyond the end of formula ratemaking by law. If the performance-based formula ratemaking framework is not extended or if Ameren Illinois elects not to participate, Ameren Illinois would then be required to establish future rates through a traditional regulatory rate review with the ICC, which might result in rates that do not produce a full or timely recovery of costs or provide for an adequate return on investments and would expose Ameren Illinois’ electric distribution business to the risks described in the immediately preceding risk factor.

The allowed ROE under both formula ratemaking recovery mechanisms is based on the annual average of the monthly yields of the 30-year United States Treasury bonds plus 580 basis points. Therefore, Ameren Illinois’ annual ROE for its electric distribution business is directly correlated to the yields on such bonds, which are outside of Ameren Illinois’ control. With respect to electric distribution service, a 50 basis point change in the annual average of the monthly yields of the 30-year United States Treasury bonds would result in an estimated $10 million change in Ameren’s and Ameren Illinois’ annual net income, based on its 2021 projected rate base.

Ameren Illinois is also subject to performance standards. Failure to achieve the standards would result in a reduction in the company’s allowed ROE calculated under the ratemaking formulas. The performance standards applicable to electric distribution service include improvements in service reliability to reduce both the frequency and duration of outages, a reduction in the number of estimated bills, a reduction of consumption from inactive meters, and a reduction in bad debt expense. The electric distribution service regulatory framework provides for ROE penalties up to 38 basis points annually in 2021 and 2022 if these performance standards are not met. The allowed ROE on energy-efficiency investments can be increased or decreased up to 200 basis points, depending on the achievement of annual energy savings goals. Any adjustments to the allowed ROE for energy-efficiency investments will depend on annual performance for a historical period relative to energy savings goals. In 2020, 2019, and 2018, there were no performance-related basis point adjustments that materially affected financial results.

Ameren Illinois plans to invest up to approximately $100 million per year in electric energy-efficiency programs through 2025, and will earn a return on those investments.While the ICC has approved a plan consistent with this spending level through 2021, the ICC has the ability to reduce the amount of electric energy-efficiency savings goals in future plan program years if there are insufficient cost-effective programs available, which could reduce the investments in electric energy-efficiency programs.

The QIP provides Ameren Illinois with recovery of, and a return on, qualifying natural gas infrastructure investments that are placed in service between regulatory rate reviews. Infrastructure investments under the QIP earn a return at the applicable WACC. Ameren Illinois’ QIP is subject to a rate impact limitation of a cumulative 4% per year since the most recent delivery service rate order, with no single year exceeding 5.5%. If the rate impact limitation was met in a particular year, the amount of rate base causing the QIP rate to exceed the limitation would be exposed to regulatory lag until a year when that amount could be recovered under QIP or is added to rate base as a part of a regulatory rate review. Upon issuance of a natural gas delivery service rate order, QIP rate base is transferred to base rates and the QIP is reset to zero. Without legislative action, the QIP will sunset after December 2023. If the QIP is not extended or there is no other regulatory change, Ameren Illinois will be subject to regulatory lag on its natural gas infrastructure investments that are placed in service between regulatory rate reviews, which could adversely affect Ameren Illinois’ results of operations, financial position, and liquidity.

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As a result of the election to use the PISA, Ameren Missouri’s electric rates are subject to a rate cap.

As a result of Ameren Missouri’s election to use the PISA, its rate increases are limited to a 2.85% compound annual growth rate in the average overall customer rate per kilowatthour, based on the electric rates that became effective in April 2017, less half of the annual savings from the TCJA that was passed on to customers as approved in the July 2018 MoPSC order. Both the rate cap and the PISA election are effective through December 2023, unless Ameren Missouri requests and receives MoPSC approval of an extension through December 2028.

If rate changes from the FAC or the RESRAM riders would cause rates to temporarily exceed the2.85%rate cap, the overage would be deferred for future recovery in the next regulatory rate review; however, rates established in such regulatory rate review would be subject to the rate cap. Any deferred overages approved for recovery would be recovered in a manner consistent with costs recovered under the PISA. Increased capital investments and operating costs could cause customer rates to exceed the rate cap. In addition, a decrease in off-system sales, which are included in net energy costs, could also contribute to customer rates exceeding the rate cap. Off-system sales are affected by planned and unplanned outages at Ameren Missouri’s energy centers, and by curtailment of generation resulting from unfavorable economic conditions, among other things. Excluding customer rates under the MEEIA rider, which are not subject to the rate cap, Ameren Missouri would incur a penalty equal to the amount of deferred overage that would cause customer rates to exceed the2.85%rate cap. A penalty incurred as the result of exceeding the rate cap could adversely affect Ameren’s and Ameren Missouri’s results of operations, financial position, and liquidity.

We are subject to various environmental laws. Significant capital expenditures are required to achieve and to maintain compliance with these environmental laws. Failure to comply with these laws could result in the closing of facilities, alterations to the manner in which these facilities operate, increased operating costs, delays and increased costs of building new facilities, or exposure to fines and liabilities.

Our electric generation, transmission, and distribution operations and natural gas transmission, distribution, and storage operations must comply with a variety of environmental laws that are enforced through statutory and regulatory requirements including permitting programs implemented by federal, state, and local authorities. Depending upon the business activity of specific facilities, such laws address emissions; discharges to water bodies; the storage, handling and disposal of hazardous substances and waste materials; siting and land use requirements; and potential ecological impacts. Complex and lengthy processes are required to obtain and renew approvals, permits, and licenses for new, existing, or modified facilities. Additionally, the use and handling of various chemicals or hazardous materials require release prevention plans and emergency response procedures. Further, we are subject to risks from changing or conflicting interpretations of existing laws, modification to existing laws, and new laws.

We are also subject to liability under environmental laws that address the remediation of environmental contamination on property currently or formerly owned by us or by our predecessors, as well as property contaminated by hazardous substances that we generated. Such properties include MGP sites and third-party sites, such as landfills. Additionally, private individuals may seek to enforce environmental laws against us. They could allege injury from exposure to hazardous materials, allege a failure to comply with environmental laws, seek to compel remediation of environmental contamination, or seek to recover damages resulting from that contamination.

Environmental regulations have a significant impact on the electric utility industry and compliance with these regulations could be costly for Ameren Missouri, which operates coal-fired power plants. As of December 31, 2020, Ameren Missouri’s coal-fired energy centers represented 11% and 23% of Ameren’s and Ameren Missouri’s rate base, respectively. Clean Air Act regulations that apply to the electric utility industry include the NSPS, the CSAPR, the MATS, and the National Ambient Air Quality Standards, which are subject to periodic review for certain pollutants. Collectively, these regulations cover a variety of pollutants, such as SO2, particulate matter, NOx, mercury, toxic metals, and acid gases, and CO2 emissions from new power plants. Clean Water Act regulations govern both water intake and discharges from power plants and require evaluation of the ecological and biological impact of our operations and could require modifications to water intake structures or more stringent limitations on wastewater discharges at Ameren Missouri’s energy centers. Depending upon the scope of modifications ultimately required by state regulators, these capital expenditures could be significant. The management and disposal of coal ash is regulated as a solid waste under the Resource Conservation and Recovery Act and the CCR rule, which require the closure of our surface impoundments at Ameren Missouri’s coal-fired energy centers. The individual or combined effects of existing and new environmental regulations could result in significant capital expenditures, increased operating costs, or the closure or alteration of operations at some of Ameren Missouri’s energy centers.

In January 2011, the Department of Justice, on behalf of the EPA, filed a complaint against Ameren Missouri in the United States District Court for the Eastern District of Missouri alleging that in performing projects at its coal-fired Rush Island Energy Center in 2007 and 2010, Ameren Missouri violated provisions of the Clean Air Act and Missouri law. In January 2017, the district court issued a liability ruling and, in September 2019, entered a final order that required Ameren Missouri to install a flue gas desulfurization system at the Rush Island Energy Center and a dry sorbent injection system at the Labadie Energy Center. There were no fines in the order. In October 2019, Ameren Missouri appealed the district court’s ruling to the United States Court of Appeals for the Eighth Circuit. The district court has stayed implementation of the majority of the requirements of its order while the case is under appeal. The ultimate resolution of this matter could have a material

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adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. Among other things and subject to economic and regulatory considerations, resolution of this matter could result in increased capital expenditures for the installation of air pollution control equipment, as well as increased operations and maintenance expenses.Based upon engineering studies from October 2019, capital expenditures to comply with the district court’s order for installation of a flue gas desulfurization system at the Rush Island Energy Center are estimated at approximately $1 billion. Further, the flue gas desulfurization system would result in additional operation and maintenance expenses of $30 million to $50 million annually for the life of the energy center. Engineering studies required to develop estimated capital expenditures and estimated additional operation and maintenance expenses for the Labadie Energy Center to comply with the district court’s order will not be undertaken while the case is under appeal.

The EPA’s Affordable Clean Energy Rule repealed the Clean Power Plan and replaced it with a new rule that had established emission guidelines for states to follow in developing plans to limit CO2 emissions and identified certain efficiency measures as the best system of emission reduction for coal-fired electric generating units. In January 2021, the United States Court of Appeals for the District of Columbia Circuit vacated the Affordable Clean Energy Rule, and ruled that the EPA had the discretion to consider emission reduction measures that include efficiency measures and generation shifting to lower carbon emissions. Additional litigation including reconsideration by the entire United States Court of Appeals for the District of Columbia Circuit or an appeal to the United States Supreme Court is possible. Regardless of the outcome of such potential legal challenges, the EPA is likely to develop new regulations to address carbon emissions from coal and natural gas electric generating units, which could take years to finalize. At this time, Ameren Missouri cannot predict the outcome of legal challenges or future rulemakings. As such, the impact on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri is uncertain.

Ameren and Ameren Missouri have incurred, and expect to incur, significant costs with respect to environmental compliance and site remediation. New or revised environmental regulations, enforcement initiatives, or legislation could result in a significant increase in capital expenditures and operating costs, decreased revenues, increased financing requirements, penalties or fines, or reduced operations of some of Ameren Missouri’s coal-fired energy centers, which, in turn, could lead to increased liquidity needs and higher financing costs. Actions required to ensure that Ameren Missouri’s facilities and operations are in compliance with environmental laws could be prohibitively expensive for Ameren Missouri if the costs are not fully recovered through rates. Environmental laws could require Ameren Missouri to close or to alter significantly the operations of its energy centers. If Ameren Missouri requests recovery of capital expenditures and costs for environmental compliance through rates, the MoPSC could deny recovery of all or a portion of these costs, prevent timely recovery, or make changes to the regulatory framework in an effort to minimize rate volatility and customer rate increases. Capital expenditures and costs to comply with future legislation or regulations might result in Ameren Missouri closing coal-fired energy centers earlier than planned. If these costs are not recoverable through rates, it could lead to an impairment of assets and reduced revenues. Any of the foregoing could have an adverse effect on our results of operations, financial positions, and liquidity.

We are subject to federal regulatory compliance and proceedings, which could result in increasing costs and the potential for regulatory penalties and other sanctions.

We are subject to FERC regulations, rules, and orders, including standards required by the NERC. As owners and operators of bulk power transmission systems and electric energy centers, we are subject to mandatory NERC reliability standards, including cybersecurity standards. In addition, our natural gas transmission, distribution, and storage facilities systems are subject to PHMSA rules and regulations. Compliance with these reliability standards, rules, and regulations may subject us to higher operating costs and may result in increased capital expenditures. We may also incur higher operating costs to comply with potential new regulations issued by these regulatory bodies. If we were found not to be in compliance with these mandatory NERC reliability standards, PHMSA rules and regulations, or FERC regulations, rules, and orders, we could incur substantial monetary penalties and other sanctions, which could adversely affect our results of operations, financial position, and liquidity. The FERC can impose civil penalties of approximately $1.3 million per violation per day for violation of its regulations, rules, and orders, including mandatory NERC reliability standards. The FERC also conducts audits and reviews of Ameren Missouri’s, Ameren Illinois’, and ATXI’s accounting records to assess the accuracy of their respective formula ratemaking process, and it can require refunds to customers for previously billed amounts, with interest.

OPERATIONAL RISKS

Our results of operations, financial position, and liquidity have been and are expected to continue to be adversely affected by the international public health emergency associated with the COVID-19 pandemic.

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effect in our service territories in mid-March 2020. These orders generally required individuals to remain at home and precluded or limited the operation of businesses that were deemed nonessential. In mid-May 2020, shelter-in-place orders effective in our service territories began to be relaxed, with individuals allowed to leave their homes and nonessential businesses allowed to begin reopening. However, certain restrictions remain in place that limit individual activities and the operation of nonessential businesses. Additional restrictions may be imposed in the future. Ameren’s business operations are deemed essential and are not directly impacted by the shelter-in-place orders. As a result of the COVID-19 pandemic, economic activity has been disrupted in the service territories of Ameren Missouri and Ameren Illinois. It has also caused disruptions in the capital markets, which could adversely affect our ability to access these markets on reasonable terms and when needed. These disruptions could continue for a prolonged period of time or become more severe.

We rely on the issuance of short-term and long-term debt and equity as significant sources of liquidity and funding for capital requirements not satisfied by our operating cash flow, as well as to refinance existing long-term debt. Disruptions to the capital markets as a result of the COVID-19 pandemic could negatively affect our ability to maintain and to expand our businesses. In addition, our credit ratings may be impacted by the economic conditions of the COVID-19 pandemic. The COVID-19 pandemic could lead to events beyond our control, such as further depressed economic conditions or extreme volatility in the debt, equity, or credit markets, and might create uncertainty that could increase our cost of capital or impair or eliminate our ability to access the debt, equity, or credit markets, including our ability to draw on bank credit facilities or issue commercial paper.

As a result of the COVID-19 pandemic, we experienced and expect to continue to experience changes to our sales volumes. In 2020, compared to 2019, Ameren Missouri experienced a reduction in commercial and industrial electric sales volumes, partially offset by increased electric sales volumes to higher margin residential customers, excluding the estimated effects of weather and customer energy-efficiency programs. The COVID-19 pandemic will continue to affect Ameren Missouri’s total electric sales volumes and sales volumes by customer class beyond 2020. Assuming a ratable change in Ameren Missouri’s electric sales volumes by month, a 1% change for the calendar year 2021 to residential, commercial, and industrial customers would affect earnings per diluted share by approximately 3 cents, 2 cents, and a half-cent, respectively. The actual change in earnings per diluted share will be affected by the timing of sales volume changes due to seasonal customer rates. Pursuant to the PISA, Ameren Missouri’s electric rates are limited to a 2.85% compound annual growth rate cap. Continued long-term declines in sales volumes, along with increased capital investments and operating costs, could result in Ameren Missouri’s inability to recover amounts exceeding the rate cap. Ameren Illinois also experienced decreases in electric and natural gas sales volumes in 2020. While the revenues from Ameren Illinois’ electric distribution business, residential and small nonresidential customers of Ameren Illinois’ natural gas distribution business, and Ameren Illinois’ and ATXI’s electric transmission businesses are decoupled from changes in sales volumes, changes in sales volumes at Ameren Missouri and those associated with Ameren Illinois’ large nonresidential natural gas customers may affect net income.

Our customers’ payment for our services has been adversely affected by the COVID-19 pandemic, resulting in a decrease to our cash flow from operations. Ameren Missouri suspended disconnections for customer nonpayment and late fees in mid-March 2020, and resumed those activities for commercial and industrial customers in mid-July 2020 and residential customers in early August 2020. Ameren Illinois resumed disconnection activities for commercial and industrial customers for nonpayment in early August 2020 and residential customers in mid-September 2020, with the exception of residential customers classified as low income, expressing a financial hardship, or relying on medical equipment. Disconnections for nonpayment for these and all other residential customers are expected to begin in April 2021, which is after the annual winter moratorium period on disconnections that ends March 31, 2021. Ameren Illinois began the winter moratorium on November 18, 2020, which has historically started at the beginning of December. Ameren Illinois also resumed charging late fees to all customers in late July 2020, following the suspension of both disconnections and late fees for all customers in mid-March 2020. Future regulatory or legislative action could require suspension of customer disconnections and/or late fees, among other things, for an extended period of time. As of December 31, 2020, accounts receivable balances that were 30 days or greater past due or that were a part of a deferred payment arrangement represented 29%, 22%, and 35%, or $133 million, $40 million, and $93 million, of Ameren’s, Ameren Missouri’s, and Ameren Illinois’ customer trade receivables before allowance for doubtful accounts, respectively. As of December 31, 2019, these percentages were 18%, 18%, and 20%, or $75 million, $30 million, and $45 million, for Ameren, Ameren Missouri, and Ameren Illinois, respectively. Ameren Illinois’ electric distribution and natural gas distribution businesses have bad debt riders, which provide for recovery of bad debt write-offs, net of any subsequent recoveries. Pursuant to a June 2020 ICC order, Ameren Illinois’ electric bad debt rider provided for the recovery of bad debt expense in 2020, which reverted to the recovery of bad debt write-offs, net of any subsequent recoveries, in 2021. Ameren Missouri does not have a bad debt rider or tracker, and thus its earnings are exposed to increases in bad debt expense, absent regulatory relief. However, Ameren Missouri does not expect a material impact to earnings from increases in bad debt expense. While Ameren Missouri is seeking recovery of certain COVID-19 pandemic related costs incurred, net of savings, and forgone customer late revenues, it could be unsuccessful in obtaining regulatory approval to recover them, which may adversely affect Ameren and Ameren Missouri’s results of operations.

In addition, suppliers and contractors may not perform as provided under their contracts. This could cause delays in construction projects, or the performance of necessary maintenance to our electric and natural gas infrastructure, which could lead to failures of equipment that can result in unanticipated liabilities or unplanned outages. Delays in our construction projects could also result in reduced planned capital expenditures and decreased rate base growth.

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Also, our businesses depend on skilled professional and technical employees. Our operations could be adversely affected if a large portion of our employees contracted COVID-19 or became quarantined at the same time. This could lead to facility shutdowns and disruptions in the delivery of electricity and natural gas to our customers. In addition, remote working arrangements increase our data security risks, including loss of data related to sensitive customer, employee, financial, and operating system information, through insider or outsider actions.

Ameren cannot predict the extent or duration of the COVID-19 pandemic or its effects on the global, national, or local economy, the capital markets, or its customers, suppliers, business continuity plans, results of operations, financial position, liquidity, planned rate base growth, or sales volumes.

The construction and acquisition of, and capital improvements to, electric and natural gas utility infrastructure, along with Ameren Missouri’s ability to implement its Smart Energy Plan, which is aligned with its 2020 IRP, involve substantial risks.

We expect to make significant capital expenditures to maintain and improve our electric and natural gas utility infrastructure and to comply with existing environmental regulations. We estimate that we will invest up to $17.8 billion (Ameren Missouri – up to $9.3 billion; Ameren Illinois – up to $8.2 billion; ATXI – up to $0.2 billion) of capital expenditures from 2021 through 2025. For additional information on these estimates, see Liquidity and Capital Resources – Capital Expenditures in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, of this report. Investments in Ameren’s rate-regulated operations are expected to be recoverable from customers, but they are subject to prudence reviews and are exposed to regulatory lag of varying degrees by jurisdiction.

Our ability to complete construction projects successfully within projected estimates, including schedule, performance, and/or cost, and to implement Ameren Missouri’s Smart Energy Plan, which may include acquisition of generation facilities after they are constructed, is contingent upon many factors and subject to substantial risks. These factors include, but are not limited to, the following: project management expertise; escalating costs and/or shortages for labor, materials, and equipment, including changes to tariffs on materials; the ability of suppliers, contractors, and developers to meet contractual commitments timely; changes in the scope and timing of projects; the ability to obtain required regulatory, project, and permit approvals; the ability to obtain necessary rights-of-way, easements, and transmission connections at an acceptable cost in a timely fashion; unsatisfactory performance by the projects when completed; the inability to earn an adequate return on invested capital; the ability to raise capital on reasonable terms; and other events beyond our control, including construction delays due to weather. With respect to the transition of Ameren Missouri’s generation fleet and achievement of the carbon emission reduction targets outlined in the 2020 IRP, factors also include MoPSC approval for the retirement of energy centers and new or continued customer energy-efficiency programs; the cost of wind, solar, and other renewable generation and storage technologies; the ability to qualify for, and use, federal production or investment tax credits; changes in environmental laws or requirements, including those related to carbon emissions; and energy prices and demand.

Any of these risks could result in higher costs, the inability to complete anticipated projects, or facility closures, and could adversely affect our results of operations, financial position, and liquidity.

Our electric generation, transmission, and distribution facilities are subject to operational risks.

Our financial performance depends on the successful operation of electric generation, transmission, and distribution facilities. Operation of electric generation, transmission, and distribution facilities involves many risks, including:

•facility shutdowns due to operator error, or a failure of equipment or processes;

•longer-than-anticipated maintenance outages;

•failures of equipment that can result in unanticipated liabilities or unplanned outages, such as the unplanned outage resulting from non-nuclear operating issues related to the Callaway Energy Center’s generator;

•aging infrastructure that may require significant expenditures to operate and maintain;

•an energy center that might not be permitted to continue to operate if pollution control equipment is not installed by prescribed deadlines or does not perform as expected;

•lack of adequate water required for cooling plant operations;

•labor disputes;

•disruptions in the delivery of electricity to our customers;

•suppliers and contractors who do not perform as required under their contracts;

•failure of other operators’ facilities and the effect of that failure on our electric system and customers;

•inability to comply with regulatory or permit requirements, including those relating to environmental laws;

•handling, storage, and disposition of CCR;

•unusual or adverse weather conditions or other natural disasters, including severe storms, droughts, floods, tornadoes, earthquakes, sustained high or low temperatures, icing, solar flares, and electromagnetic pulses, such as the extremely low temperatures experienced in mid-February 2021;

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•the level of wind and solar resources;

•inability to operate wind generation facilities at full capacity resulting from requirements to protect natural resources, including wildlife;

•the occurrence of catastrophic events such as fires, explosions, acts of sabotage or terrorism, civil unrest, pandemic health events, including the COVID-19 pandemic, or other similar events;

•accidents that might result in injury or loss of life, extensive property damage, or environmental damage;

•ineffective vegetation management programs;

•cybersecurity risks, including loss of operational control of Ameren Missouri’s energy centers and our transmission and distribution systems and loss of data, including sensitive customer, employee, financial, and operating system information, through insider or outsider actions;

•limitations on amounts of insurance available to cover losses that might arise in connection with operating our electric generation, transmission, and distribution facilities;

•inability to implement or maintain information systems;

•failure to keep pace with and the ability to adapt to rapid technological change; and

•other unanticipated operations and maintenance expenses and liabilities.

The foregoing risks could affect the controls and operations of our facilities or impede our ability to meet regulatory requirements, which could increase operating costs, increase our capital requirements and costs, reduce our revenues, or have an adverse effect on our liquidity.

Ameren Missouri’s ability to obtain an adequate supply of coal could limit operation of its coal-fired energy centers.

Ameren Missouri owns and operates coal-fired energy centers. About 97% of Ameren Missouri’s coal is purchased from the Powder River Basin in Wyoming, which has a limited number of suppliers. Deliveries from the Powder River Basin have occasionally been restricted because of rail congestion and maintenance, derailments, weather, and supplier financial hardship. Coal suppliers in the Power River Basin are experiencing financial hardship because of a decrease in demand resulting from increased natural gas and renewable energy generation, and the impact of environmental regulations, as well as concerns related to coal-fired generation. These financial hardships have resulted in bankruptcy filings by certain coal suppliers in recent years. As of December 31, 2020, coal inventories for Ameren Missouri were near targeted levels. However, disruptions in the delivery of coal, failure of our coal suppliers to provide adequate quantities or quality of coal, or lack of adequate inventories of coal, including low-sulfur coal used to comply with environmental regulations, could have adverse effects on Ameren Missouri’s electric generation operations. If Ameren Missouri is unable to obtain an adequate supply of coal under existing agreements, it may be required to purchase coal at higher prices or be forced to reduce generation at its coal-fired energy centers, which could adversely affect Ameren’s and Ameren Missouri’s results of operations, financial position, and liquidity.

Ameren Missouri’s ownership and operation of a nuclear energy center creates business, financial, and waste disposal risks.

Ameren Missouri’s ownership of the Callaway Energy Center subjects it to risks associated with nuclear generation, including:

•potential harmful effects on the environment and human health resulting from radiological releases associated with the operation of nuclear facilities and the storage, handling, and disposal of radioactive materials;

•continued uncertainty regarding the federal government’s plan to permanently store spent nuclear fuel and, as a result, the need to provide for long-term storage of spent nuclear fuel at the Callaway Energy Center;

•limitations on the amounts and types of insurance available to cover losses that might arise in connection with the Callaway Energy Center or other United States nuclear facilities;

•uncertainties about contingencies and retrospective premium assessments relating to claims at the Callaway Energy Center or any other United States nuclear facilities;

•public and governmental concerns about the safety and adequacy of security at nuclear facilities;

•limited availability of fuel supply and our reliance on licensed fuel assemblies from the one NRC-licensed supplier of Callaway Energy Center’s assemblies;

•costly and extended outages for scheduled or unscheduled maintenance and refueling;

•uncertainties about the technological and financial aspects of decommissioning nuclear facilities at the end of their licensed lives;

•the adverse effect of poor market performance and other economic factors on the asset values of nuclear decommissioning trust funds and the corresponding increase, upon MoPSC approval, in customer rates to fund the estimated decommissioning costs; and

•potential adverse effects of a natural disaster, acts of sabotage or terrorism, including a cyber attack, or any accident leading to a radiological release.

The NRC has broad authority under federal law to impose licensing and safety requirements for nuclear facilities. In the event of noncompliance, the NRC has the authority to impose fines or to shut down a unit, or both, depending upon its assessment of the severity of the situation, until compliance is achieved. Revised safety requirements promulgated from time to time by the NRC could necessitate substantial capital expenditures at the Callaway Energy Center. In addition, if a serious nuclear incident were to occur, it could adversely affect Ameren’s and Ameren Missouri’s results of operations, financial condition, and liquidity. A major incident at a nuclear facility anywhere

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in the world could cause the NRC to limit or prohibit the operation of any domestic nuclear unit and could also cause the NRC to impose additional conditions or requirements on the industry, which could increase costs and result in additional capital expenditures. NRC standards relating to seismic risk require Ameren Missouri to further evaluate the impact of an earthquake on its Callaway Energy Center due to its proximity to a fault line, which could require the installation of additional capital equipment.

Our natural gas distribution and storage activities involve numerous risks that may result in accidents and increased operating costs.

Inherent in our natural gas distribution and storage activities are a variety of hazards and operating risks, such as leaks, explosions, mechanical problems and cybersecurity risks, which could cause substantial financial losses, including fines and penalties. In addition, these hazards could result in serious injury, loss of human life, significant damage to property, environmental impacts, and impairment of our operations, which in turn could lead us to incur substantial losses. The location of distribution mains and storage facilities near populated areas, including residential areas, business centers, industrial sites, and other public gathering places, could increase the level of damages resulting from these risks. A major domestic incident involving natural gas distribution, and storage systems could result in additional capital expenditures and/or increased operations and maintenance expenses for us and increased regulation of natural gas utilities. The occurrence of any of these events could adversely affect our results of operations, financial position, and liquidity.

Significant portions of our electric generation, transmission, and distribution facilities and natural gas transmission and distribution facilities are aging. This aging infrastructure may require significant additional maintenance or replacement. Ameren Missouri could be adversely affected if it is unable to recover the remaining investment, if any, and decommissioning costs associated with the retirement of an energy center, as well as the ability to earn a return on that remaining investment and those decommissioning costs.

Our aging infrastructure may pose risks to system reliability and expose us to expedited or unplanned significant capital expenditures and operating costs. All of Ameren Missouri’s coal-fired energy centers were constructed prior to 1978, and the Callaway Energy Center began operating in 1984. The age of these energy centers increases the risks of unplanned outages, reduced generation output, and higher maintenance expense. Further, Ameren Missouri would be adversely affected if the MoPSC does not allow recovery of the remaining investment and decommissioning costs associated with the retirement of an energy center, as well as the ability to earn a return on that remaining investment and those decommissioning costs. As indicated it its 2020 IRP, Ameren Missouri intends to advance the retirement dates of the Sioux and Rush Island coal-fired energy centers to 2028 and 2039, respectively, which are subject to the approval of a change in the assets’ depreciable lives by the MoPSC in a future regulatory rate review. Aging transmission and distribution facilities are more prone to failure than new facilities, which results in higher maintenance expense and the need to replace these facilities with new infrastructure. Even if the system is properly maintained, its reliability may ultimately deteriorate and negatively affect our ability to serve our customers, which could result in increased costs associated with regulatory oversight. The frequency and duration of customer outages are among the IEIMA performance standards. Any failure to achieve these standards will result in a reduction in Ameren Illinois’ allowed ROE on electric distribution assets. The higher maintenance costs associated with aging infrastructure and capital expenditures for new or replacement infrastructure could cause additional rate volatility for our customers, resistance by our regulators to allow customer rate increases, and/or regulatory lag in some of our jurisdictions, any of which could adversely affect our results of operations, financial position, and liquidity.

Energy conservation, energy efficiency, distributed generation, energy storage, technological advances, and other factors could reduce energy demand from our customers.

Without a regulatory mechanism to ensure recovery, declines in energy usage could result in an under-recovery of our revenue requirement or an increase in our customer rates, as the revenue requirement would be spread over less sales volumes, which could adversely affect our results of operations, financial position, and liquidity. Such declines could occur due to a number of factors, including:

•customer energy-efficiency programs that are designed to reduce energy demand;

•energy-efficiency efforts by customers not related to our energy-efficiency programs;

•increased customer use of distributed generation sources, such as solar panels and other technologies, which have become more cost-competitive, with decreasing costs expected in the future, as well as the use of energy storage technologies; and

•macroeconomic factors resulting in low economic growth or contraction within our service territories, which could reduce energy demand.

Decreased use of our generation, transmission, and distribution services might result in stranded costs, which ultimately might not be recovered through rates, and therefore, could lead to an impairment of assets.

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FINANCIAL, ECONOMIC, AND MARKET RISKS

Ameren’s holding company structure could limit its ability to pay common stock dividends and to service its debt obligations.

Ameren is a holding company; therefore, its primary assets are its investments in the common stock of its subsidiaries, including Ameren Missouri, Ameren Illinois, and ATXI. As a result, Ameren’s ability to pay dividends on its common stock depends on the earnings of its subsidiaries and the ability of its subsidiaries to pay dividends or otherwise transfer funds to Ameren. Similarly, Ameren’s ability to service its debt obligations is dependent upon the earnings of its operating subsidiaries and the distribution of those earnings and other payments, including payments of principal and interest under affiliate indebtedness. The payment of dividends to Ameren by its subsidiaries in turn depends on their results of operations, and other items affecting retained earnings, and available cash. Ameren’s subsidiaries are separate and distinct legal entities and have no obligation, contingent or otherwise, to pay any dividends or make any other distributions (except for payments required pursuant to the terms of affiliate borrowing arrangements and cash payments under the tax allocation agreement) to Ameren. Certain financing agreements, corporate organizational documents, and certain statutory and regulatory requirements may impose restrictions on the ability of Ameren Missouri, Ameren Illinois, and ATXI to transfer funds to Ameren in the form of cash dividends, loans, or advances.

Costs associated with our defined benefit retirement and postretirement plans, health care plans, and other employee benefits could increase.

Ameren has defined benefit pension plans covering substantially all of its employees and has postretirement benefit plans covering non-union employees hired before October 2015 and union employees hired before January 2020. Assumptions related to future costs, returns on investments, interest rates, timing of employee retirements, and mortality, as well as other actuarial matters, have a significant impact on our customers’ rates and our plan funding requirements. Ameren’s total pension and postretirement benefit plans were overfunded by $249 million as of December 31, 2020. Ameren expects to fund its pension plans at a level equal to the greater of the pension cost or the legally required minimum contribution. Based on Ameren’s assumptions at December 31, 2020, its investment performance in 2020, and its pension funding policy, Ameren expects to make aggregate contributions of $60 million over the next five years. Ameren Missouri’s and Ameren Illinois’ portions of the future funding requirements are estimated to be 30% and 60%, respectively. These estimates may change with actual investment performance, changes in interest rates, changes in our assumptions, changes in government regulations, and any voluntary contributions.

In addition to the costs of our pension plans, the costs of providing health care benefits to our employees and retirees have increased in recent years. We believe that our employee benefit costs, including costs of health care plans for our employees and former employees, will continue to rise. Future legislative changes related to health care could also significantly change our benefit programs and costs. The increasing costs and funding requirements associated with our defined benefit retirement plans, health care plans, and other employee benefits could increase our financing needs and otherwise adversely affect our financial position and liquidity.

GENERAL RISKS

Customers’, investors’, legislators’, and regulators’ opinions of us are affected by many factors, including system reliability, implementation of our strategic plan, protection of customer information, rates, media coverage, and environmental, social, and governance practices, as well as actions by other utility companies. Negative opinions developed by customers, investors, legislators, or regulators could harm our reputation.

Service interruptions and facility shutdowns can occur due to failures of equipment as a result of severe or destructive weather or other causes. The ability of Ameren Missouri and Ameren Illinois to respond promptly to such failures can affect customer satisfaction. In addition to system reliability issues, the success of modernization efforts, our ability to safeguard sensitive customer information and protect our systems from cyber attacks, and other actions can affect customer satisfaction. The level of rates, the timing and magnitude of rate increases, and the volatility of rates can also affect customer satisfaction.

Our ability to successfully execute our strategic plan, including the transition of Ameren Missouri’s generation fleet and achievement of the carbon emission reduction targets outlined in the 2020 IRP, may affect customers’, investors’, legislators’, and regulators’ opinions and actions. Additionally, negative perceptions or publicity resulting from increasing scrutiny of environmental, social, and governance practices could negatively impact our reputation, investment in our common stock, or our access to capital markets. Customers’, investors’, legislators’, and regulators’ opinions of us can also be affected by media coverage, including social media, which may include information, whether factual or not, that damages our brand and reputation.

If customers, investors, legislators, or regulators have or develop a negative opinion of us and our utility services, this could result in increased costs associated with regulatory oversight and could affect the ROEs we are allowed to earn, as well as the access to, and the cost of, capital. Additionally, negative opinions about us or other utility companies could make it more difficult for our businesses to achieve

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favorable legislative or regulatory outcomes. Negative opinions could also result in sales volume reductions or increased use of distributed generation by our customers. Any of these consequences could adversely affect our results of operations, financial position, and liquidity.

We are subject to employee work force factors that could adversely affect our operations.

Our businesses depend upon our ability to employ and retain key officers and other skilled professional and technical employees. Certain specialized knowledge that focuses on skilled-craft and STEM-related disciplines is required to construct and operate generation, transmission, and distribution assets. Further, a significant portion of our work force is nearing retirement. We are also party to collective bargaining agreements that collectively represent about 48% of Ameren’s total employees. Certain events, such as an aging workforce without adequately trained replacement employees, the mismatch of skill sets to future needs, or any work stoppage experienced in connection with negotiations of collective bargaining agreements, could adversely affect our operations.

Our operations are subject to acts of terrorism, cyber attacks, and other intentionally disruptive acts.

Like other electric and natural gas utilities, our energy centers, fuel storage facilities, transmission and distribution facilities, and information systems may be affected by terrorist activities and other intentionally disruptive acts, including cyber attacks, which could disrupt our ability to produce or distribute our energy products. There have been attacks on energy infrastructure, such as substations and related assets, in the past, and there may be more attacks in the future as technology becomes more prevalent in energy infrastructure. Any such incident could limit our ability to generate, purchase, or transmit power or natural gas and could have significant regional economic consequences. Any such disruption could result in a significant decrease in revenues, a significant increase in costs including those for repair, or adversely affect economic activity in our service territory which, in turn, could adversely affect our results of operations, financial position, and liquidity.

There has been an increase in the number and sophistication of cyber attacks across all industries worldwide. Cyber attacks could include viruses, malicious or destructive code, phishing attacks, denial of service attacks, ransomware and other ransom-based attacks, improper access by third parties, attacks on email systems, and ransom demands to not expose sensitive data, operational control, or security vulnerabilities specific to our systems, among various other security breaches. A security breach at our physical assets or in our information systems could affect the reliability of the transmission and distribution system, disrupt electric generation, including nuclear generation, and/or subject us to financial harm resulting from theft or the inappropriate release or destruction of certain types of information, including sensitive customer, employee, financial, and operating system information. Many of our suppliers, vendors, contractors, and information technology providers have access to systems that support our operations and maintain customer and employee data. A breach of these third-party systems could adversely affect our business as if it was a breach of our own system. If a significant breach occurred, our reputation could be adversely affected, customer confidence could be diminished, and/or we could be subject to increased costs associated with regulatory oversight, fines or legal claims, any of which could result in a significant decrease in revenues or significant costs for remedying the impacts of such a breach. Our generation, transmission, and distribution systems are part of an interconnected system. Therefore, a disruption caused by a cyber incident at another utility, electric generator, RTO, or commodity supplier could also adversely affect our businesses. Insurance might not be adequate to cover losses that arise in connection with these events. In addition, new regulations could require changes in our security measures and result in increased costs. The occurrence of any of these events could adversely affect our results of operations, financial position, and liquidity.

Our businesses are dependent on our ability to access the capital markets successfully. We might not have access to sufficient capital in the amounts and at the times needed, as well as on reasonable terms.

We rely on the issuance of short-term and long-term debt and equity as significant sources of liquidity and funding for capital requirements not satisfied by our operating cash flow, as well as to refinance existing long-term debt. The inability to raise debt or equity capital on reasonable terms, or at all, could negatively affect our ability to maintain or to expand our businesses. Events beyond our control, such as depressed economic conditions, the COVID-19 pandemic, or extreme volatility in the debt, equity, or credit markets, might create uncertainty that could increase our cost of capital or impair or eliminate our ability to access the debt, equity, or credit markets, including our ability to draw on bank credit facilities. Any adverse change in our credit ratings could reduce access to capital and trigger collateral postings and prepayments. Such changes could also increase the cost of borrowing and the costs of fuel, power, and natural gas supply, among other things, which could adversely affect our results of operations, financial position, and liquidity.

ITEM 1B. UNRESOLVED STAFF COMMENTS

None.

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ITEM 2.PROPERTIES

For information on our principal properties, see the energy center table below. See also Liquidity and Capital Resources and Regulatory Matters in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, of this report for a discussion of planned additions, replacements, or transfers. See also Note 5 – Long-term Debt and Equity Financings and Note 14 – Commitments and Contingencies under Part II, Item 8, of this report.

The following table shows the anticipated capability of Ameren Missouri’s energy centers at the time of Ameren Missouri’s expected 2021 peak summer electrical demand for all energy centers owned as of December 31, 2020:

Primary Fuel Source Energy Center Location Net Kilowatt Capability(a)

Coal Labadie(b) Franklin County, Missouri 2,372,000

Rush Island(c) Jefferson County, Missouri 1,178,000

Sioux(c) St. Charles County, Missouri 972,000

Meramec(c) St. Louis County, Missouri 540,000

Nuclear Callaway(d) Callaway County, Missouri 1,194,000

Hydroelectric Osage(d) Lakeside, Missouri 235,000

Pumped-storage Taum Sauk(d) Reynolds County, Missouri 440,000

Wind(e) High Prairie Adair and Schuyler Counties, Missouri 400,000

Natural gas Audrain(f) Audrain County, Missouri 616,000

Venice Venice, Illinois 495,000

Goose Creek Piatt County, Illinois 444,000

Pinckneyville Pinckneyville, Illinois 316,000

Raccoon Creek Clay County, Illinois 308,000

Meramec(c)(g) St. Louis County, Missouri 226,000

Kinmundy Kinmundy, Illinois 210,000

Peno Creek(f) Bowling Green, Missouri 192,000

Oil (CTs) Fairgrounds(c) Jefferson City, Missouri 55,000

Mexico(c) Mexico, Missouri 55,000

Moberly(c) Moberly, Missouri 55,000

Moreau(c) Jefferson City, Missouri 55,000

Methane gas (CT) Maryland Heights Maryland Heights, Missouri 8,000

Solar O’Fallon O’Fallon, Missouri 4,500

Lambert St. Louis County, Missouri 1,000

BJC St. Louis, Missouri 1,500

Total Ameren and Ameren Missouri 10,521,000

(a)Net kilowatt capability, except for wind and solar generating facilities, is the generating capacity available for dispatch from the energy center into the electric transmission grid. Capability for wind and solar facilities represents nameplate capacity. This capacity is only attainable when wind/solar conditions are sufficiently available. The on-demand capability for wind and solar units is zero.

(b)The Labadie Energy Center is scheduled to retire 1,186,000 kilowatts by 2036 and 1,186,000 kilowatts by 2042.

(c)The Rush Island, Sioux, and Meramec energy centers are scheduled to retire by 2039, 2028, and 2022, respectively. The retirement dates of the Rush Island and Sioux energy centers are proposed to be advanced from their previous retirement dates of 2045 and 2033, respectively, as part of the 2020 IRP. The Fairgrounds, Mexico, Moberly, and Moreau energy centers are scheduled to be retired by 2026 as part of the 2020 IRP. Advancing the retirement date of an energy center is subject to the approval of a change in the assets’ depreciable lives by the MoPSC in a future regulatory rate review.

(d)The operating licenses for the Callaway, Osage, and Taum Sauk energy centers expire in 2044, 2047, and 2044, respectively.

(e)Ameren Missouri acquired the Atchison Renewable Energy Center in January 2021. As of the date of this filing, 120,000 kilowatts were in service. Ameren Missouri expects approximately 150,000 kilowatts of the up-to 300,000-kilowatt project to be in service by the end of the first quarter of 2021, and the remaining portion to be in service later in 2021.

(f)There are economic development arrangements applicable to these CTs, as discussed below.

(g)Its two operating units are steam-powered.

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The following table presents in-service electric and natural gas utility-related properties for Ameren Missouri and Ameren Illinois as of December 31, 2020:

AmerenMissouri AmerenIllinois

Circuit miles of electric transmission lines(a) 3,150 4,662

Circuit miles of electric distribution lines 34,122 46,911

Percentage of circuit miles of electric distribution lines underground 24 % 16 %

Miles of natural gas transmission and distribution mains 3,466 18,565

Underground natural gas storage fields — 12

(a)ATXI owns 544 miles of transmission lines not reflected in this table.

Our other properties include office buildings, warehouses, garages, and repair shops.

With only a few exceptions, we have fee title to all principal energy centers and other units of property material to the operation of our businesses, and to the real property on which such facilities are located (subject to mortgage liens securing our outstanding first mortgage bonds and to certain permitted liens and judgment liens). The exceptions are as follows:

•Certain property is situated on lands occupied under leases, easements, franchises, licenses, or permits. That property includes a portion of Ameren Missouri’s Osage Energy Center reservoir; certain facilities at Ameren Missouri’s Sioux Energy Center; most of Ameren Missouri’s High Prairie Renewable, Atchison Renewable, Peno Creek CT and Audrain CT energy centers; Ameren Missouri’s Maryland Heights, Lambert, and BJC energy centers; certain substations; and most transmission and distribution lines and natural gas mains. The United States or the state of Missouri may own or may have paramount rights with respect to certain lands lying in the bed of the Osage River or located between the inner and outer harbor lines of the Mississippi River on which certain of Ameren Missouri’s energy centers and other properties are located.

•The United States, the state of Illinois, the state of Iowa, or the city of Keokuk, Iowa, may own or may have paramount rights with respect to certain lands lying in the bed of the Mississippi River on which a portion of Ameren Missouri’s Keokuk Energy Center is located.

Substantially all of the properties and plant of Ameren Missouri and Ameren Illinois are subject to the liens of the indentures securing their mortgage bonds.

Ameren Missouri has conveyed most of its Peno Creek CT Energy Center to the city of Bowling Green, Missouri through December 2022. Ameren Missouri has rights and obligations as the operator of the energy center under a long-term agreement with the city of Bowling Green. Under the terms of this agreement, Ameren Missouri is responsible for all operation and maintenance for the energy center. Ownership of the energy center will transfer to Ameren Missouri at the expiration of the agreement, at which time the property, plant, and equipment will become subject to the lien of the Ameren Missouri mortgage bond indenture.

Ameren Missouri operates a CT energy center located in Audrain County, Missouri. Ameren Missouri has rights and obligations as the operator of the energy center under a long-term agreement with Audrain County. Under the terms of this agreement, Ameren Missouri is responsible for all operation and maintenance for the energy center. The agreement will expire in December 2023. Ownership of the energy center will transfer to Ameren Missouri at the expiration of the agreement, at which time the property, plant, and equipment will become subject to the lien of the Ameren Missouri mortgage bond indenture.

ITEM 3.LEGAL PROCEEDINGS

We are involved in legal and administrative proceedings before various courts and agencies with respect to matters that arise in the ordinary course of business, some of which involve substantial amounts of money. We believe that the final disposition of these proceedings, except as otherwise disclosed in this report, will not have a material adverse effect on our results of operations, financial position, or liquidity. Risk of loss is mitigated, in some cases, by insurance or contractual or statutory indemnification. We believe that we have established appropriate reserves for potential losses. For additional information on material legal and administrative proceedings, see Note 2 – Rate and Regulatory Matters, Note 9 – Callaway Energy Center, and Note 14 – Commitments and Contingencies under Part II, Item 8, of this report. Pursuant to Item 103(c)(3)(iii) of Regulation S-K, our policy is to disclose environmental proceedings to which a governmental entity is a party if we reasonably believe such proceedings will result in monetary sanctions of $1 million or more.

ITEM 4.MINE SAFETY DISCLOSURES

Not applicable.

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INFORMATION ABOUT OUR EXECUTIVE OFFICERS:

The executive officers of the Ameren Companies, including major subsidiaries, are listed below, along with their ages as of December 31, 2020, all their positions and offices held with the Ameren Companies as of February 22, 2021, their tenures as officers, and their business backgrounds for at least the last five years. Some executive officers hold multiple positions within the Ameren Companies; their titles are given in the description of their business experience.

AMEREN CORPORATION:

Name Age Positions and Offices Held

Michael L. Moehn 51 Executive Vice President and Chief Financial Officer

Chonda J. Nwamu 49 Senior Vice President, General Counsel, and Secretary

Bruce A. Steinke 59 Senior Vice President, Finance, and Chief Accounting Officer

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SUBSIDIARIES:

Name Age Positions and Offices Held

Mary P. Heger 64 Senior Vice President, Customer Experience (Ameren Illinois)

Richard J. Mark 65 Chairman and President (Ameren Illinois)

Martin J. Lyons, Jr. 54 Chairman and President (Ameren Missouri)

Shawn E. Schukar 59 Chairman and President (ATXI)

Officers are generally elected or appointed annually by the respective board of directors of each company, following the election of board members at the annual meetings of shareholders. No special arrangement or understanding exists between any of the above-named executive officers and the Ameren Companies nor, to our knowledge, with any other person or persons pursuant to which any executive officer was selected as an officer. There are no family relationships among the executive officers or between any executive officers and any directors of the Ameren Companies. Except as noted, the above-named executive officers have been employed by an Ameren company for more than five years in executive or management positions.

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PART II

ITEM 5.MARKET FOR REGISTRANTS’ COMMON EQUITY, RELATED STOCKHOLDER MATTERS, AND ISSUER PURCHASE OF EQUITY SECURITIES

Ameren’s common stock is listed on the NYSE (ticker symbol: AEE). Ameren common shareholders of record totaled 42,072 on January 29, 2021. There is no trading market for the common stock of Ameren Missouri and Ameren Illinois. Ameren holds all outstanding common stock of Ameren Missouri and Ameren Illinois.

Purchases of Equity Securities

Ameren Corporation, Ameren Missouri, and Ameren Illinois did not purchase any equity securities reportable under Item 703 of Regulation S-K during the period from October 1, 2020, to December 31, 2020.

Performance Graph

The following graph shows Ameren’s cumulative TSR during the five years ended December 31, 2020. The graph also shows the cumulative total returns of the S&P 500 Index, S&P 500 Utility Index, and the Philadelphia Utility Index. The S&P 500 Utility Index and the Philadelphia Utility Index are market capitalization-weighted indices of U.S. public utility companies. The comparison assumes that $100 was invested on December 31, 2015, in Ameren common stock and in each of the indices shown and that all of the dividends were reinvested.

Comparison of Five-Year Cumulative Return

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Ameren management cautions that the stock price performance shown above should not be considered indicative of future stock price performance.

ITEM 6.SELECTED FINANCIAL DATA

Ameren has early adopted the SEC’s Disclosure Modernization Final Rule, effective February 10, 2021, for Item 301 of Regulation S-K. As such, Item 6 – Selected Financial Data has not been provided.

ITEM 7.MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

Ameren, headquartered in St. Louis, Missouri, is a public utility holding company whose primary assets are its equity interests in its subsidiaries.Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. Dividends on Ameren’s common stock and the payment of expenses by Ameren depend on distributions made to it by its subsidiaries.

Below is a summary description of Ameren’s principal subsidiaries – Ameren Missouri, Ameren Illinois, and ATXI. Ameren also has other subsidiaries that conduct other activities, such as providing shared services. A more detailed description can be found in Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of this report.

•Ameren Missouri operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri.

•Ameren Illinois operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois.

•ATXI operates a FERC rate-regulated electric transmission business in the MISO.

Ameren has four segments: Ameren Missouri, Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Transmission. The Ameren Missouri segment includes all of the operations of Ameren Missouri. Ameren Illinois Electric Distribution consists of the electric distribution business of Ameren Illinois. Ameren Illinois Natural Gas consists of the natural gas business of Ameren Illinois. Ameren Transmission primarily consists of the aggregated electric transmission businesses of Ameren Illinois and ATXI. See Note 16 – Segment Information under Part II, Item 8, of this report for further discussion of Ameren’s and Ameren Illinois’ segments.

Ameren’s financial statements are prepared on a consolidated basis and therefore include the accounts of its majority-owned subsidiaries. All intercompany transactions have been eliminated, except as disclosed inNote 13 – Related-party Transactions under Part II, Item 8, of this report. Ameren Missouri and Ameren Illinois have no subsidiaries. All tabular and graphical dollar amounts are in millions, unless otherwise indicated.

The following discussion should be read in conjunction with the financial statements contained in this Form 10-K. We intend for this discussion to provide the reader with information that will assist in understanding our financial statements, the changes in certain key items in those financial statements, and the primary factors that accounted for those changes, as well as how certain accounting principles affect our financial statements. The discussion also provides information about the financial results of our business segments to provide a better understanding of how those segments and their results affect the financial condition and results of operations of Ameren as a whole. Discussion regarding our financial condition and results of operations for the year ended December 31, 2018, including comparisons with the year ended December 31, 2019, is included in Item 7 of our Form 10-K for the year ended December 31, 2019, filed with the SEC on February 28, 2020.

In addition to presenting results of operations and earnings amounts in total, we present certain information in cents per share. These amounts reflect factors that directly affect Ameren’s earnings. We believe this per share information helps readers to understand the impact of these factors on Ameren’s earnings per share.

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OVERVIEW

Our core strategy is driven by the following three pillars:

Customer Rates, (¢/KWH)(e)

Segment Regulatory Framework

AmerenTransmission Formula ratemakingAllowed ROE is 10.52%

(a) Reflects year-end rate base except for Ameren Transmission, which is average rate base.

(b) Compound annual growth rate.

(d) Allowed ROE applicable to electric service.

(e) Average residential electric prices. Source: Edison Electric Institute, “Typical Bills and Average Rates Report” for the 12 months ended June 30, 2020.

(f) Ameren management cautions that the stock price performance shown above should not be considered indicative of future stock price performance.

Key announcements, updates, and regulatory outcomes

The COVID-19 pandemic continues to be a constantly evolving situation. In 2020, we experienced a net decrease in our sales volumes, an increase in our accounts receivable balances that were past due or that were a part of a deferred payment arrangement, and a decline in our cash collections from customers. The continued effect of the COVID-19 pandemic on our results of operations, financial position, and liquidity in subsequent periods will depend on its severity and longevity, future regulatory or legislative actions with respect thereto, and the resulting impact on business, economic, and capital market conditions. Shelter-in-place orders began taking effect in our service territories in mid-March 2020. These orders generally required individuals to remain at home and precluded or limited the operation of businesses that were deemed nonessential. In early 2020, Ameren began implementing its business continuity plans, and continues to take measures to mitigate the risk of COVID-19 transmission. Actions included restricting travel for employees, implementing work-from-home policies, securing and supplying personal protective equipment, and implementing work practices to protect the safety of our employees and customers. While our business operations were deemed essential and were not directly impacted by the shelter-in-place orders, approximately 65% of our workforce transitioned to remote working arrangements in mid-March 2020. In order to work more effectively in certain areas, a portion of our workforce returned to our work locations in early June 2020 under a phased approach, and, as of the date of this filing, approximately 50% of our workforce continues to work remotely. In mid-May 2020, shelter-in-place orders effective in our service territories began to be relaxed, with fewer restrictions on social activities and nonessential businesses beginning to reopen. However, certain

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restrictions remain in place that limit individual activities and the operation of nonessential businesses. Additional restrictions may be imposed in the future. We continue to assess the impacts the pandemic is having on our businesses, including impacts on electric and natural gas sales volumes, liquidity, and bad debt expense, among other things. For further discussion of these and other matters, see Note 1 – Summary of Significant Accounting Policies and Note 2 – Rate and Regulatory Mattersunder Part II, Item 8, of this report, and Results of Operations, Liquidity and Capital Resources, and Outlook sections below. In addition, for information regarding Ameren Missouri’s and Ameren Illinois’ suspensions and reinstatement of customer disconnection activities and late fee charges for nonpayment, see Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report.

In February 2020, the MoPSC issued an order approving a stipulation and agreement allowing Ameren Missouri to defer and amortize maintenance expenses related to scheduled refueling and maintenance outages at its Callaway Energy Center. Maintenance expenses associated with the fall 2020 refueling and maintenance outage were deferred as a regulatory asset. Amortization of those expenses began in January 2021, and will be amortized until the completion of the next refueling and maintenance outage. During its return to full power after the completion of the last refueling and maintenance outage in late December 2020, the Callaway Energy Center experienced a non-nuclear operating issue related to its generator. A thorough investigation of this matter was conducted. Work has begun to replace certain key components of the generator in order to return the energy center to service. Ameren Missouri expects generator repairs of $65 million, which are expected to be largely capital expenditures. Due to the long lead time for the manufacture, repair, and installation of the components, the energy center is expected to return to service in late June or early July 2021. See Note 9 – Callaway Energy Center under Part II, Item 8, of this report for additional information.

In March 2020, the MoPSC issued an order in Ameren Missouri’s July 2019 electric service regulatory rate review, approving nonunanimous stipulation and agreements. The order resulted in a decrease of $32 million to Ameren Missouri’s annual revenue requirement for electric retail service, which reflected infrastructure investments as of December 31, 2019. The order also provided for the continued use of the FAC and trackers for pension and postretirement benefits, uncertain income tax positions, and certain excess deferred income taxes that the MoPSC previously authorized in earlier electric rate orders. In addition, the order required Ameren Missouri to donate $8 million to low-income assistance programs, which was reflected in results of operations in the first quarter of 2020.The new rates became effective on April 1, 2020.

In August 2020, the MoPSC issued an order approving a unanimous stipulation and agreement with respect to the 2022 program year of Ameren Missouri’s six-year MEEIA 2019 program and related performance incentives. The order also approved Ameren Missouri’s energy savings results for the first year of the MEEIA 2019 program. As a result of this order and in accordance with revenue recognition guidance, Ameren Missouri recognized revenues of $6 million in the third quarter of 2020.

In September 2020, Ameren Missouri filed its 2020 IRP with the MoPSC. In connection with the 2020 IRP filing, Ameren established a goal of achieving net-zero carbon emissions by 2050. Ameren is also targeting a 50% CO2 emission reduction by 2030 and an 85% reduction by 2040 from the 2005 level. The plan, which is subject to review by the MoPSC for compliance with Missouri law, targets cleaner and more diverse sources of energy generation, including solar, wind, hydro, and nuclear power, and supports increased investment in new energy technologies. It also includes expanding renewable sources by adding 3,100 MWs of renewable generation by the end of 2030 and a total of 5,400 MWs of renewable generation by 2040. These amounts include the 700 MWs of wind generation projects discussed below, which will support Ameren Missouri’s compliance with the state of Missouri’s requirement of achieving 15% of native load sales from renewable energy sources beginning in 2021. The plan also includes advancing the retirement dates of the Sioux and Rush Island coal-fired energy centers to 2028 and 2039, respectively, which are subject to the approval of a change in the assets’ depreciable lives by the MoPSC in a future regulatory rate review, the continued implementation of customer energy-efficiency programs, and the expectation that Ameren Missouri will seek NRC approval for an extension of the operating license for the Callaway Energy Center beyond its current 2044 expiration date. Additionally, the plan includes retiring the Meramec and Labadie coal-fired energy centers at the end of their useful lives (by 2022 and 2042, respectively).

In October 2020, Ameren Missouri filed requests with the MoPSC for accounting authority orders related to its electric and natural gas services. If issued as requested, the orders would allow Ameren Missouri to accumulate certain costs incurred related to the COVID-19 pandemic, including bad debt write-offs, net of cost savings, as well as forgone customer late fee and reconnection fee revenues, for a specified time period, for potential recovery in future electric and natural gas service regulatory rate reviews. Costs incurred, net of savings, and forgone customer late fee and reconnection fee revenues related to the COVID-19 pandemic from March 2020 through December 2020 were immaterial. The MoPSC is under no deadline to issue orders, and Ameren Missouri cannot predict the ultimate outcome of these regulatory proceedings.

In December 2020, Ameren Missouri acquired a 400-MW wind generation project located in northeastern Missouri for approximately $615 million, and placed the assets in service as the High Prairie Renewable Energy Center. In January 2021, Ameren Missouri acquired an up-to 300-MW wind generation project located in northwestern Missouri. At the date of this filing, Ameren Missouri placed 120 MWs in service as the Atchison Renewable Energy Center, with a purchase price of approximately $200 million. There have been changes to the schedule

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for this project, particularly as a result of component delivery delays. Ameren Missouri expects approximately 150 MWs of the up-to 300-MW project to be in service by the end of the first quarter of 2021, and the remaining portion to be in service later in 2021.

In February 2021, Ameren Missouri filed an update to its Smart Energy Plan with the MoPSC, which includes a five-year capital investment overview with a detailed one-year plan for 2021. The plan is designed to upgrade Ameren Missouri’s electric infrastructure and includes investments that will upgrade the grid and accommodate more renewable energy. Investments under the plan are expected to total approximately $8.4 billion over the five-year period from 2021 through 2025, with expenditures largely recoverable under the PISA and the RESRAM. The planned investments in 2024 and 2025 are based on the assumption that Ameren Missouri requests and receives MoPSC approval of an extension of the PISA through December 2028.

In December 2020, the ICC issued an order in Ameren Illinois’ annual update filing that approved a $49 million decrease in Ameren Illinois’ electric distribution service rates beginning in January 2021. This order reflected a decrease to the annual formula rate based on 2019 actual costs, a decrease to include the 2019 revenue requirement reconciliation adjustment, and a decrease for the conclusion of the 2018 revenue requirement reconciliation adjustment, which was fully collected from customers in 2020, consistent with the ICC’s December 2019 annual update filing order. It also reflected an increase based on expected net plant additions for 2020.

In January 2021, the ICC issued an order in Ameren Illinois’ February 2020 natural gas delivery service regulatory rate review, which resulted in an increase to its annual revenues for natural gas delivery service of $76 million, based on a 9.67% allowed ROE, a capital structure composed of 52% common equity, and a rate base of $2.1 billion. The new rates became effective in January 2021. As a result of this order, the rate base under the QIP was reset to zero. Ameren Illinois used a 2021 future test year in this proceeding.

In October 2020, Ameren’s board of directors increased the quarterly common stock dividend to 51.5 cents per share. In February 2021, the board increased the quarterly common stock dividend to 55 cents per share, resulting in an annualized equivalent dividend rate of $2.20 per share.

Earnings

Net income attributable to Ameren common shareholders was $871 million, or $3.50 per diluted share, for 2020, and $828 million, or $3.35 per diluted share, for 2019. Net income was favorably affected in 2020, compared with 2019, by the results of Ameren Missouri’s March 2020 electric rate order; infrastructure investments that drove higher earnings at Ameren Transmission, Ameren Illinois Electric Distribution, and Ameren Illinois Natural Gas; and increased Ameren Transmission earnings resulting from the May 2020 FERC order addressing the allowed base ROE. Earnings in 2020, compared with 2019, were also favorably affected by lower other operations and maintenance expenses not subject to riders or trackers, primarily due to the absence in 2020 of expenses related to the Callaway Energy Center’s 2019 scheduled refueling and maintenance outage; and by lower electric system infrastructure maintenance expenses as a result of decreased system load, disciplined cost management, and the deferral of projects to future periods. Net income was unfavorably affected in 2020, compared with 2019, by decreased electric retail sales at Ameren Missouri largely due to the COVID-19 pandemic, and due to milder summer and warmer winter temperatures in 2020; higher net financing costs at Ameren Missouri and Ameren (parent); lower revenues due to reduced MEEIA performance incentives at Ameren Missouri; and a lower recognized ROE at Ameren Illinois Electric Distribution.

Liquidity

At December 31, 2020, Ameren, on a consolidated basis, had available liquidity in the form of cash on hand and amounts available under the Credit Agreements of $1.9 billion.

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Ameren remains focused on strategic capital allocation. The following chart presents 2020 capital expenditures by segment and the midpoint of projected cumulative capital expenditures for 2021 through 2025 by segment:

Ameren Missouri(a) Ameren Illinois Natural Gas

Ameren Illinois Electric Distribution Ameren Transmission

(a)Ameren Missouri capital expenditures include $564 million for the acquisition of the High Prairie Renewable Energy Center for the year ended December 31, 2020.

For 2021 through 2025, Ameren’s cumulative capital expenditures are projected to range from $16.4 billion to $17.8 billion. The following table presents the range of projected spending by segment:

Range (in billions)

Ameren Missouri(a) $ 8.7 – $ 9.3

Ameren Illinois Electric Distribution 2.6 – 2.8

Ameren Illinois Natural Gas 1.7 – 1.8

Ameren Transmission 3.5 – 3.8

(a)Amounts include 300 MWs of wind generation at the Atchison Renewable Energy Center, but exclude incremental renewable generation investment opportunities of 1,200 MWs by 2025, which are included in Ameren Missouri’s 2020 IRP.

RESULTS OF OPERATIONS

Our results of operations and financial position are affected by many factors. Economic conditions, including those resulting from the COVID-19 pandemic discussed below, energy-efficiency investments by our customers and by us, technological advances, distributed generation, and the actions of key customers can significantly affect the demand for our services. Ameren and Ameren Missouri results are also affected by seasonal fluctuations in winter heating and summer cooling demands, as well as by energy center maintenance outages. Additionally, fluctuations in interest rates and conditions in the capital and credit markets affect our cost of borrowing, and our pension and postretirement benefits costs. Almost all of Ameren’s revenues are subject to state or federal regulation. This regulation has a material impact on the rates we charge customers for our services. Our results of operations, financial position, and liquidity are affected by our ability to align our overall spending, both operating and capital, with the frameworks established by our regulators. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for additional information regarding Ameren Missouri’s, Ameren Illinois’, and ATXI’s regulatory frameworks.

We continue to assess the impacts of the COVID-19 pandemic on our businesses, including impacts on electric and natural gas sales volumes, supply chain operations, and bad debt expense. Ameren Missouri and Ameren Illinois suspended customer disconnections and late

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fee charges for nonpayment in mid-March 2020 and began resuming these activities, with certain exceptions, in the third quarter of 2020. For additional information on Ameren Missouri’s and Ameren Illinois’ reinstatement of customer disconnection and late fee charges for non-payment, see Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report. With respect to uncollectible accounts receivable, Ameren Illinois’ electric distribution and natural gas distribution businesses have bad debt riders, which provide for recovery of bad debt write-offs, net of any subsequent recoveries. Pursuant to a June 2020 ICC order, Ameren Illinois’ electric bad debt rider provided for the recovery of bad debt expense in 2020, which reverted to the recovery of bad debt write-offs, net of any subsequent recoveries, in 2021. Ameren Missouri does not have a bad debt rider or tracker, and thus its earnings are exposed to increases in bad debt expense, absent regulatory relief. However, Ameren Missouri does not expect a material impact to earnings from increases in bad debt expense. In October 2020, Ameren Missouri filed requests with the MoPSC for accounting authority orders related to certain impacts resulting from the COVID-19 pandemic. If issued as requested, the orders would allow Ameren Missouri to accumulate certain costs incurred related to the COVID-19 pandemic, including bad debt write-offs, net of cost savings, as well as forgone customer late fee and reconnection fee revenues, for a specified time period, for potential recovery in future electric and natural gas service regulatory rate reviews.As of December 31, 2020, accounts receivable balances that were 30 days or greater past due or that were a part of a deferred payment arrangement represented 29%, 22%, and 35%, or $133 million, $40 million, and $93 million, of Ameren’s, Ameren Missouri’s, and Ameren Illinois’ customer trade receivables before allowance for doubtful accounts, respectively. As of December 31, 2019, these percentages were 18%, 18%, and 20%, or $75 million, $30 million, and $45 million, for Ameren, Ameren Missouri, and Ameren Illinois, respectively. Ameren Missouri’s electric sales volumes have been, and continue to be, affected by the COVID-19 pandemic. In 2020, compared to 2019, Ameren Missouri experienced a reduction in commercial and industrial electric sales volumes, partially offset by increased electric sales volumes to higher margin residential customers, excluding the estimated effects of weather and customer energy-efficiency programs. For 2021, Ameren Missouri expects gradual improvement in economic activities to result in increased electric sales volumes, excluding the estimated effects of weather and customer energy-efficiency programs. The table below provides the increases and (decreases) in Ameren Missouri electric sales volumes by customer class for 2020, compared to 2019, and the estimated increases and (decreases) for 2021, compared to 2020, excluding the estimated effects of weather and customer energy-efficiency programs:

Ameren Missouri Customer Class

Residential 3.0 % 1 %

Commercial (7.0) % 2 %

Industrial (2.1) % 3 %

Total (2.2) % 2 %

Assuming a ratable change in Ameren Missouri’s electric sales volumes by month, a 1% change for the calendar year 2021 to residential, commercial, and industrial customers would affect earnings per diluted share by approximately 3 cents, 2 cents, and a half-cent, respectively. The actual change in earnings per diluted share will be affected by the timing of sales volume changes due to seasonal customer rates.

Ameren Missouri principally uses coal and enriched uranium for fuel in its electric operations and purchases natural gas for its customers. Ameren Illinois purchases power and natural gas for its customers. The prices for these commodities can fluctuate significantly because of the global economic and political environment, weather, supply, demand, and many other factors. We have natural gas cost recovery mechanisms for our Illinois and Missouri natural gas distribution businesses, a purchased power cost recovery mechanism for Ameren Illinois’ electric distribution business, and a FAC for Ameren Missouri’s electric business.

We employ various risk management strategies to reduce our exposure to commodity risk and other risks inherent in our business. The reliability of Ameren Missouri’s energy centers and our transmission and distribution systems and the level and timing of operations and maintenance costs and capital investment are key factors that we seek to manage in order to optimize our results of operations, financial position, and liquidity.

Earnings Summary

The following table presents a summary of Ameren’s earnings for the years ended December 31, 2020 and 2019:

Net income attributable to Ameren common shareholders $ 871 $ 828

Earnings per common share – diluted 3.50 3.35

Net income attributable to Ameren common shareholders in 2020 increased $43 million, or $0.15 per diluted share, from 2019. The increase was due to net income increases of $31 million, $15 million, and $10 million, at Ameren Transmission, Ameren Illinois Natural Gas, and Ameren Missouri, respectively. The increases in net income were partially offset by an increase in the net loss for activity not reported as part of a segment, primarily at Ameren (parent) of $10 million and a decrease in net income at Ameren Illinois Electric Distribution of $3 million.

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Earnings per share in 2020, compared with 2019, were favorably affected by:

•lower base level of expenses, partially offset by lower base rates, net of recovery for amounts associated with the reduction in sales volumes resulting from MEEIA programs and recoverable depreciation under the PISA, at Ameren Missouri pursuant to the March 2020 MoPSC electric rate order as discussed in Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report (23 cents per share);

•increased rate base investments, which increased earnings at Ameren Transmission and Ameren Illinois Electric Distribution, including energy-efficiency investments at Ameren Illinois (14 cents per share);

•decreased Callaway Energy Center scheduled refueling and maintenance expenses, due to the treatment of the 2019 scheduled refueling and maintenance outage costs at the Callaway Energy Center, which were expensed as incurred, as compared with the deferral of expenses for the fall 2020 scheduled refueling and maintenance outage pursuant to the February 2020 MoPSC order, which decreased other operations and maintenance expenses (10 cents per share);

•decreased system load, disciplined cost management, the deferral of projects to future periods, and decreased other costs not recoverable under riders or trackers, excluding decreased costs associated with the Callaway Energy Center’s scheduled refueling and maintenance outage, which decreased other operations and maintenance expenses (10 cents per share);

•the result of the May 2020 FERC order addressing the allowed base ROE for FERC regulated transmission rate base under the MISO tariff, which increased Ameren Transmission earnings (4 cents per share); and

•increased investments in qualifying infrastructure recovered under the QIP, which increased earnings at Ameren Illinois Natural Gas (4 cents per share).

Earnings per share in 2020, compared with 2019, were unfavorably affected by:

•lower MEEIA performance incentives recognized at Ameren Missouri (9 cents per share);

•increased net financing costs at Ameren (parent) and Ameren Missouri, primarily due to higher long-term debt balances (9 cents per share);

•decreased electric retail sales, excluding the estimated effects of weather, at Ameren Missouri, largely due to the COVID-19 pandemic, which decreased sales volumes and demand charge revenue from commercial and industrial customers, partially offset by increased sales volumes to higher margin residential customers (8 cents per share);

•the impact of weather on electric retail sales at Ameren Missouri, primarily resulting from milder summer and warmer winter temperatures experienced in 2020 (estimated at 7 cents per share);

•a lower recognized ROE at Ameren Illinois Electric Distribution under performance-based formula ratemaking driven by lower annual average monthly yields on 30-year United States Treasury bonds (7 cents per share);

•increased charitable donations, primarily at Ameren Missouri, which included an increase of 2 cents per share pursuant to its March 2020 electric rate order (4 cents per share);

•decreased electric margins from transmission services, and customer late fees and reconnection fees at Ameren Missouri, largely due to the COVID-19 pandemic (3 cents per share);

•decreased income tax benefits at Ameren (parent) related to stock-based compensation (3 cents per share);

•increased depreciation and amortization expenses not recoverable under riders or trackers at Ameren Missouri, primarily due to additional property, plant, and equipment investments (2 cents per share); and

•increased weighted-average basic common shares outstanding (2 cents per share).

The cents per share information presented is based on the weighted-average basic shares outstanding in 2019 and does not reflect any change in earnings per share resulting from dilution, unless otherwise noted. Amounts other than variances related to income taxes have been presented net of income taxes using Ameren’s 2020 statutory tax rate of 26%. For additional details regarding the Ameren Companies’ results of operations, including explanations of Electric and Natural Gas Margins, Other Operations and Maintenance Expenses, Depreciation and Amortization, Taxes Other Than Income Taxes, Other Income, Net, Interest Charges, and Income Taxes, see the major headings below.

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Below is Ameren’s table of income statement components by segment for the years ended December 31, 2020 and 2019:

Noncontrolling interests – preferred stock dividends (3) (1) (1) (1) — (6)

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Below is Ameren Illinois’ table of income statement components by segment for the years ended December 31, 2020 and 2019:

Natural gas margins — 531 — 531

Other operations and maintenance expenses (506) (221) (48) (775)

Depreciation and amortization (288) (81) (65) (434)

Taxes other than income taxes (72) (65) (3) (140)

Preferred stock dividends (1) (1) (1) (3)

Net income attributable to common shareholder $ 143 $ 99 $ 137 $ 379

Natural gas margins — 519 — 519

Other operations and maintenance expenses (498) (233) (51) (782)

Depreciation and amortization (273) (78) (55) (406)

Taxes other than income taxes (73) (67) (3) (143)

Preferred stock dividends (1) (1) (1) (3)

Net income attributable to common shareholder $ 146 $ 84 $ 113 $ 343

Margins

Electric margins are defined as electric revenues less fuel and purchased power costs. Natural gas margins are defined as natural gas revenues less natural gas purchased for resale. We consider electric and natural gas margins useful measures to analyze the change in profitability of our electric and natural gas operations between periods. We have included the analysis below as a complement to the financial information we provide in accordance with GAAP. However, these margins may not be a presentation defined under GAAP, and they may not be comparable to other companies’ presentations or more useful than the GAAP information we provide elsewhere in this report.

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Electric Margins

Total by Segment(a) Increase (Decrease) by Segment

(Overall Ameren Increase of $18 Million)

(a)Includes other/intersegment eliminations of $(29) million and $(29) million in 2020and 2019, respectively.

Natural Gas Margins

Total by Segment(a) Increase (Decrease) by Segment

(Overall Ameren Increase of $13 Million)

(a)Includes other/intersegment eliminations of $(2) million and $(2) million in 2020and 2019, respectively.

Ameren Missouri Ameren Illinois Natural Gas

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The following table presents the favorable (unfavorable) variations by segment for electric and natural gas margins in 2020, compared with 2019:

Electric and Natural Gas Margins

Electric revenue change:

Effect of weather (estimate)(b) $ (30) $ — $ — $ — $ — $ (30)

Base rates (estimate)(c) (58) (3) — 59 — (2)

Customer demand charges (7) — — — — (7)

MEEIA performance incentives (31) — — — — (31)

Off-system sales 47 — — — — 47

Customer late fees and reconnection fees (4) — — — — (4)

Energy-efficiency program investments — 12 — — — 12

Transmission service revenues (3) — — — — (3)

Other cost recovery mechanisms(e) 2 3 — — — 5

Total electric revenue change $ (125) $ (6) $ — $ 59 $ 2 $ (70)

Fuel and purchased power change:

Effect of weather (estimate)(b) 8 — — — — 8

Effect of lower net energy costs included in base rates 92 — — — — 92

Transmission service charges (3) — — — — (3)

Other — — — — (2) (2)

Cost recovery mechanisms – offset in electric revenue(d) 4 23 — — — 27

Total fuel and purchased power change $ 67 $ 23 $ — $ — $ (2) $ 88

Net change in electric margins $ (58) $ 17 $ — $ 59 $ — $ 18

Natural gas revenue change:

Effect of weather (estimate)(b) $ (5) $ — $ — $ — $ — $ (5)

Software licensing agreement — — (5) — — (5)

Other 3 — (1) — — 2

Other cost recovery mechanisms(e) (1) — (5) — — (6)

Total natural gas revenue change $ (9) $ — $ (37) $ — $ — $ (46)

Natural gas purchased for resale change:

Effect of weather (estimate)(b) $ 4 $ — $ — $ — $ — $ 4

Cost recovery mechanisms – offset in natural gas revenue(d) 6 — 49 — — 55

Total natural gas purchased for resale change $ 10 $ — $ 49 $ — $ — $ 59

Net change in natural gas margins $ 1 $ — $ 12 $ — $ — $ 13

(a)Includes an increase in transmission electric margins of $41 million in 2020, compared with 2019, at Ameren Illinois.

(b)Represents the estimated variation resulting primarily from changes in cooling and heating degree days on electric and natural gas demand compared with the prior year; this variation is based on temperature readings from the National Oceanic and Atmospheric Administration weather stations at local airports in our service territories.

(c)For Ameren Illinois Electric Distribution and Ameren Transmission, base rates include increases or decreases to operating revenues related to the revenue requirement reconciliation adjustment under formula rates. For Ameren Missouri, base rates exclude an increase of $43 million for the recovery of lost electric margins in 2020, compared with 2019, resulting from the MEEIA 2016 and 2019 customer energy-efficiency programs. This amount is included in the “sales volumes and changes in customer usage patterns (excluding the estimated effects of weather and MEEIA)” line item.

(d)Electric and natural gas revenue changes are offset by corresponding changes in “Fuel,” “Purchased power,” and “Natural gas purchased for resale” on the statement of income, resulting in no change to electric and natural gas margins.

(e)Offsetting expense increases or decreases are reflected in “Other operations and maintenance,” “Depreciation and amortization,” or in “Taxes other than income taxes,” within the “Operating Expenses” section of the statement of income. These items have no overall impact on earnings.

Ameren

Ameren’s electric margins increased $18 million, or less than 1%, in 2020, compared with 2019, primarily because of increased margins at Ameren Transmission and Ameren Illinois Electric Distribution, partially offset by decreased margins at Ameren Missouri, as discussed

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below. Ameren’s natural gas margins increased $13 million, or 2%, between years primarily because of increased margins at Ameren Illinois Natural Gas, as discussed below.

Ameren Transmission

Ameren Transmission’s electric margins increased $59 million, or 13%, in 2020, compared with 2019. Margins were favorably affected by increased capital investment, as evidenced by a 13% increase in the 13-month average rate base used to calculate the revenue requirement between years, and an increase in the allowed ROE resulting from the May 2020 FERC order. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for additional information regarding the May 2020 FERC order.

Ameren Missouri

Ameren Missouri’s electric margins decreased $58 million, or 2%, in 2020, compared with 2019. Ameren Missouri’s natural gas margins were comparable between years.

The following items had an unfavorable effect on Ameren Missouri’s electric margins in 2020, compared with 2019:

•The aggregate effect of changes in customer usage, excluding the estimated effects of weather and the MEEIA customer energy-efficiency programs, decreased electric revenues an estimated $43 million. The decrease was primarily due to a reduction in sales volumes (-$44 million) and decreased revenues from customer demand charges (-$7 million), both of which were unfavorably affected by the COVID-19 pandemic. An increase in the average retail price per kilowatthour due to changes in customer usage patterns partially offset the decreases by a favorable $8 million. While the MEEIA customer energy-efficiency programs reduced retail sales volumes, the recovery of lost electric margins under the MEEIA ensured that electric margins were not affected.

•The absence of revenues associated with MEEIA 2013 and 2016 performance incentives in 2020, partially offset by revenues from the MEEIA 2019 performance incentive, decreased revenues $31 million. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for information regarding the MEEIA performance incentives.

•Summer temperatures were milder as cooling degree days decreased 7%, and winter temperatures were warmer as heating degree days decreased 9%. The aggregate effect of weather decreased margins by an estimated $22 million. The change in margins due to weather is the sum of the “Effect of weather (estimate)” on electric revenues (-$30 million) and the “Effect of weather (estimate)” on fuel and purchased power (+$8 million) in the table above.

•Additional investments made by other transmission entities contributed to increased transmission service charges of $3 million and lower system load contributed to decreased transmission service revenues of $3 million.

•In response to the COVID-19 pandemic, suspensions of customer late fees and reconnection fees resulted in a $4 million decrease in revenue. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for information on the suspension of customer late fees and disconnections.

The following items had a favorable effect on Ameren Missouri’s electric margins in 2020, compared with 2019:

•The March 2020 MoPSC electric rate order, with new rates effective April 1, 2020, increased margins $34 million. The change in electric base rates is the sum of the “Change in base rates (estimate)” (-$58 million) and the “Effect of lower net energy costs included in base rates” (+$92 million) in the table above.

•Decreased sales volumes, which were affected by the COVID-19 pandemic, resulted in lower net energy costs and increased margins $13 million. The change in net energy costs is the sum of the effect of the revenue change in “Off-system sales” (+$47 million) and the “Effect of the change in energy costs” (-$34 million) in the table above.

Ameren Illinois

Ameren Illinois’ electric margins increased $58 million, or 4%, in 2020, compared with 2019, driven by increased margins at Ameren Illinois Transmission (+$41 million) and Ameren Illinois Electric Distribution (+$17 million). Ameren Illinois Natural Gas’ margins increased $12 million, or 2%, between years.

Ameren Illinois Electric Distribution

Ameren Illinois Electric Distribution’s margins increased $17 million, or 2%, in 2020, compared with 2019. Revenues increased $12 million due to increased energy-efficiency program investments under performance-based formula ratemaking. Margins decreased due to a lower recognized ROE (-$17 million), as evidenced by a decrease of 102 basis points in the annual average of the monthly yields of the 30-year United States Treasury bonds, partially offset by increased capital investment (+$8 million), as evidenced by a 6% increase in year-end rate base, and higher recoverable non-purchased power expenses (+$6 million). The sum of these base rate changes collectively decreased margins $3 million in 2020, compared with 2019.

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Ameren Illinois Natural Gas

Ameren Illinois Natural Gas’ margins increased $12 million, or 2%, in 2020, compared with 2019. Revenues from increased QIP recoveries due to additional investment in qualified natural gas infrastructure increased margins $23 million. The absence of revenues from a software licensing agreement with Ameren Missouri decreased margins $5 million. See the Software Licensing Agreement section within Note 13 – Related-party Transactions under Part II, Item 8, of this report for information regarding this transaction.

Ameren Illinois Transmission

Ameren Illinois Transmission’s electric margins increased $41 million, or 14%, in 2020, compared with 2019. Margins were favorably affected by increased capital investment, as evidenced by a 19% increase in the 13-month average rate base between years, and an increase in the allowed ROE resulting from the May 2020 FERC order. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for additional information regarding the May 2020 FERC order.

Other Operations and Maintenance Expenses

Total by Segment(a) Increase (Decrease) by Segment

(Overall Ameren Decrease of $84 Million)

(a)Includes $57 million and $60 million at Ameren Transmission in 2020 and 2019, respectively, and other/intersegment eliminations of $(9) million and $(6) million in 2020and 2019, respectively.

Ameren Missouri Ameren Illinois Natural Gas Other/Intersegment Eliminations

Ameren Illinois Electric Distribution Ameren Transmission

Ameren

Other operations and maintenance expenses were $84 million lower in 2020, compared with 2019. In addition to changes by segments discussed below, other operations and maintenance expenses decreased $3 million in 2020 for activity not reported as part of a segment, as reflected in “Other/Intersegment Eliminations” above, primarily because of decreased costs for support services.

Ameren Transmission

Other operations and maintenance expenses were $3 million lower in 2020, compared with 2019, primarily due to a decrease in transmission expenditures at Ameren Illinois Transmission resulting from disciplined cost management.

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Ameren Missouri

The $74 million decrease in other operations and maintenance expenses in 2020, compared with 2019, was primarily due to the following items:

•Callaway Energy Center refueling operations and maintenance costs decreased $34 million, due to the treatment of the 2019 scheduled refueling and maintenance outage costs at the Callaway Energy Center, which were expensed as incurred, as compared with the deferral of expenses for the fall 2020 scheduled refueling and maintenance outage pursuant to the February 2020 MoPSC order.

•Energy center maintenance costs, other than those associated with the Callaway refueling and maintenance outage, decreased $29 million, primarily because of lower electric system infrastructure maintenance expenses as a result of decreased system load, disciplined cost management, and the deferral of projects to future periods.

•Transmission and distribution expenditures decreased $15 million, primarily resulting from less maintenance due to recent capital improvements and disciplined cost management.

•Amortization of solar rebate costs incurred prior to the RESRAM decreased $13 million as a result of the March 2020 MoPSC electric rate order.

The following items partially offset the above decreases in other operations and maintenance expenses between years:

•Solar rebate costs recoverable under the RESRAM increased $9 million, primarily because of the amortization of previously-deferred rebates included in customer rates in 2020.

•Bad debt costs increased $7 million, primarily because of an increase in accounts receivable balances that were past due or that were a part of a deferred payment arrangement, which increased primarily due to the COVID-19 pandemic.

•Technology-related expenditures increased $5 million, primarily because of costs associated with the implementation of cloud computing technology.

Ameren Illinois

Other operations and maintenance expenses were $7 million lower at Ameren Illinois in 2020, compared with 2019, as discussed below.

Ameren Illinois Electric Distribution

The $8 million increase in other operations and maintenance expenses in 2020, compared with 2019, was primarily due to the following items:

•Amortization of energy-efficiency program investments under performance-based formula ratemaking increased $8 million.

•Labor and benefit costs increased $8 million, primarily because of higher pension costs.

The following items partially offset the above increases in other operations and maintenance expenses between years:

•Meter reading costs decreased $4 million, as deployment of automated smart meters was substantially completed in 2019.

•Distribution expenditures decreased $3 million, primarily because of lower storm costs.

Ameren Illinois Natural Gas

The $12 million decrease in other operations and maintenance expenses in 2020, compared with 2019, was primarily due to a $4 million reduction in costs recovered through riders and a $4 million reduction in meter reading costs, as deployment of automated smart meters was substantially completed in 2019. Other operations and maintenance expenses also decreased because of a $4 million reduction in distribution expenditures due to disciplined cost management.

Ameren Illinois Transmission

The $3 million decrease in other operations and maintenance expenses in 2020, compared with 2019, was primarily due to a decrease in transmission expenditures resulting from disciplined cost management.

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Depreciation and Amortization

Total by Segment(a) Increase (Decrease) by Segment

(Overall Ameren Increase of $80 Million)

(a)Includes other/intersegment eliminations of $4 million and $4 million in 2020 and 2019, respectively.

Ameren Missouri Ameren Illinois Natural Gas Other/Intersegment Eliminations

Ameren Illinois Electric Distribution Ameren Transmission

The $80 million, $48 million, and $28 million increase in depreciation and amortization expenses in 2020, compared with 2019, at Ameren, Ameren Missouri, and Ameren Illinois, respectively, was primarily due to additional property, plant, and equipment across their respective segments. Ameren’s and Ameren Missouri’s depreciation and amortization expenses reflected a deferral to a regulatory asset of depreciation and amortization expenses pursuant to the PISA. The PISA deferral of depreciation and amortization expenses was $27 million and $24 million in 2020 and 2019, respectively.

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Taxes Other Than Income Taxes

Total by Segment(a) Increase (Decrease) by Segment

(Overall Ameren Increase of $2 Million)

(a)Includes $8 million and $4 million at Ameren Transmission in 2020 and 2019, respectively, and other/intersegment eliminations of $10 million and $8 million in 2020and2019, respectively.

Ameren Missouri Ameren Illinois Natural Gas Other/Intersegment Eliminations

Ameren Illinois Electric Distribution Ameren Transmission

Taxes other than income taxes were comparable at Ameren between 2020 and 2019. Excise taxes decreased $8 million and $4 million at Ameren Missouri and Ameren Illinois Natural Gas, respectively, because of reduced sales. These decreases were mostly offset by increases of $7 million and $4 million in property taxes at Ameren Missouri and Ameren Transmission, respectively, primarily due to higher assessed property values. See Excise Taxes in Note 15 – Supplemental Information under Part II, Item 8, of this report for additional information.

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Other Income, Net

Total by Segment Increase (Decrease) by Segment

(Overall Ameren Increase of $21 Million)

Ameren Missouri Ameren Illinois Natural Gas Other/Intersegment Eliminations

Ameren Illinois Electric Distribution Ameren Transmission

Other income, net, increased $21 million at Ameren in 2020, compared with 2019. An increase of $28 million in the non-service cost components of net periodic benefit income at Ameren Missouri was partially offset by a $9 million increase in donations, primarily due to charitable donations made pursuant to the March 2020 MoPSC electric rate order. Additionally, other income, net, increased because of a $4 million increase in the equity portion of allowance for funds used during construction at Ameren Transmission. See Note 6 – Other Income, Net under Part II, Item 8, of this report for additional information. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for additional information regarding Ameren Missouri’s March 2020 electric rate order. See Note 10 – Retirement Benefits under Part II, Item 8, of this report for more information on the non-service cost components of net periodic benefit income.

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Interest Charges

Total by Segment Increase (Decrease) by Segment

(Overall Ameren Increase of $38 Million)

Ameren Missouri Ameren Illinois Natural Gas Other/Intersegment Eliminations

Ameren Illinois Electric Distribution Ameren Transmission

Interest charges increased $38 million in 2020, compared with 2019, primarily because of a long-term debt issuance at Ameren (parent) in April 2020, which increased interest charges by $21 million, which was partially offset by a decrease associated with the reduction in average short-term debt outstanding, as proceeds from the long-term debt issuance were used to repay outstanding short-term debt. Interest charges also increased due to long-term debt issuances at Ameren Missouri in March 2020 and October 2020, partially offset by lower average interest rates applicable to long-term debt, which increased interest charges by $14 million. Interest charges at Ameren Missouri reflected a deferral to a regulatory asset of interest charges pursuant to PISA. The PISA deferral of interest charges was $12 million and $15 million in 2020 and 2019, respectively.

Income Taxes

The following table presents effective income tax rates for the years ended December 31, 2020and 2019:

Ameren Missouri 7% 14%

Ameren Illinois 24% 24%

Ameren Illinois Electric Distribution 22% 23%

Ameren Illinois Natural Gas 26% 26%

Ameren Illinois Transmission 25% 24%

Ameren Transmission 26% 25%

See Note 12 – Income Taxes under Part II, Item 8, of this report for information regarding reconciliations of effective income tax rates for Ameren, Ameren Missouri, and Ameren Illinois. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for information regarding reductions in revenues related to the lower federal statutory corporate income tax rate enacted under the TCJA and the return of excess deferred income taxes to customers.

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LIQUIDITY AND CAPITAL RESOURCES

Collections from our tariff-based revenues are our principal source of cash provided by operating activities. A diversified retail customer mix, primarily consisting of rate-regulated residential, commercial, and industrial customers, provides us with a reasonably predictable source of cash. In addition to using cash provided by operating activities, we use available cash, drawings under committed credit agreements, commercial paper issuances, and/or, in the case of Ameren Missouri and Ameren Illinois, short-term affiliate borrowings to support normal operations and temporary capital requirements. We may reduce our short-term borrowings with cash provided by operations or, at our discretion, with long-term borrowings, or, in the case of Ameren Missouri and Ameren Illinois, with capital contributions from Ameren (parent). We expect to make significant capital expenditures over the next five years as we invest in our electric and natural gas utility infrastructure to support overall system reliability, grid modernization, renewable energy targets requirements, environmental compliance, and other improvements. As part of its plan to fund these cash flow requirements, Ameren is using newly issued shares of common stock, rather than market-purchased shares, to satisfy requirements under the DRPlus and employee benefit plans and expects to continue to do so through at least 2025. Ameren expects these issuances to provide equity of about $100 million annually. In addition to the issuance of common shares in connection with the 2021 settlement of the remaining portion of the forward sale agreement, Ameren plans to issue incremental equity of about $150 million in 2021 and about $300 million each year from 2022 to 2025. Ameren expects its equity to total capitalization to be about 45% through December 31, 2025, with the long-term intent to support solid investment-grade credit ratings.

The use of cash provided by operating activities and short-term borrowings to fund capital expenditures and other long-term investments at the Ameren Companies frequently results in a working capital deficit, defined as current liabilities exceeding current assets, as was the case at December 31, 2020, for Ameren and Ameren Illinois. With the credit capacity available under the Credit Agreements, and cash and cash equivalents, Ameren (parent), Ameren Missouri, and Ameren Illinois, collectively had net available liquidity of $1.9 billion at December 31, 2020. As a result of capital market volatility, due, in part, to the COVID-19 pandemic, and to increase net available liquidity, Ameren (parent) accelerated a debt issuance to April 2020, which had been planned for later in 2020, and used a portion of the proceeds to repay $350 million of senior unsecured notes held by Ameren (parent) in October 2020. Also, in August 2019, Ameren entered into a forward sale agreement with a counterparty relating to 7.5 million shares of common stock. In December 2020, Ameren partially settled the forward sale agreement by physically delivering 5.9 million shares of common stock for cash proceeds of $425 million. In February 2021, Ameren settled the remainder of the forward sale agreement by physically delivering 1.6 million shares of common stock for cash proceeds of $113 million. The proceeds were used to fund a portion of Ameren Missouri’s wind generation investments. See Credit Facility Borrowings and Liquidity and Long-term Debt and Equity below for additional information.

The following table presents net cash provided by (used in) operating, investing, and financing activities for the years ended December 31, 2020 and 2019:

Cash Flows from Operating Activities

Our cash provided by operating activities is affected by fluctuations of trade accounts receivable, inventories, and accounts and wages payable, among other things, as well as the unique regulatory environment for each of our businesses. Substantially all expenditures related to fuel, purchased power, and natural gas purchased for resale are recovered from customers through riders, which may be adjusted without a traditional regulatory rate review, subject to prudence reviews. Similar regulatory mechanisms exist for certain operating expenses that can also affect the timing of cash provided by operating activities. The timing of cash payments for costs recoverable under our regulatory mechanisms differs from the recovery period of those costs. Additionally, the seasonality of our electric and natural gas businesses, primarily caused by seasonal customer rates and changes in customer demand due to weather, significantly affect the amount and timing of our cash provided by operating activities. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for more information about our regulatory frameworks.

Our customers’ payment for our services has been adversely affected by the COVID-19 pandemic, resulting in a decrease to our cash flow from operations. For information regarding Ameren Missouri’s and Ameren Illinois’ suspensions and reinstatement of customer disconnection activities and late fee charges for nonpayment, see Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report. In addition, see Results of Operations above for more information on Ameren’s, Ameren Missouri’s, and Ameren Illinois’ accounts receivable balances that were 30 days or greater past due or that were a part of a deferred payment arrangement.

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Ameren

Ameren’s cash provided by operating activities decreased $443 million in 2020, compared with 2019. The following items contributed to the decrease:

•A $381 million decrease resulting from reduced customer collections, primarily resulting from a decrease in sales volumes and an increase in accounts receivable balances, which were primarily due to the COVID-19 pandemic, and a net decrease attributable to regulatory recovery mechanisms, partially offset by decreased fuel and purchased power costs at Ameren Missouri and decreased purchased power costs and volumes, and natural gas costs, at Ameren Illinois.

•A $38 million increase in payments to settle ARO liabilities, primarily related to Ameren Missouri’s CCR storage facilities.

•A $28 million increase in pension and postretirement benefit plan contributions.

•A $27 million decrease in net collateral activity with counterparties, primarily resulting from changes in the market prices of power and natural gas, changes in contracted commodity volumes, and decreases resulting from Ameren Illinois’ renewable energy contracts entered into pursuant to the FEJA.

•A $25 million decrease, primarily resulting from increases to materials and supplies to support operations as levels were increased in 2020 to mitigate against any potential supply disruptions associated with the COVID-19 pandemic.

•A $16 million increase in interest payments, primarily due to an increase in the average outstanding debt at Ameren (parent) and Ameren Illinois.

•A $13 million increase in property tax payments at Ameren Missouri due to higher assessed property tax values.

•Refunds paid in 2020 of $13 million associated with the November 2013 FERC complaint case, as discussed in Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report.

The following items partially offset the decrease in Ameren’s cash from operating activities between periods:

•A $37 million decrease in payroll tax payments primarily due to the employer portion of Social Security taxes as a result of a payment deferral allowed under the Coronavirus Aid, Relief, and Economic Security Act. Half of this deferral will be paid at the end of 2021 and the remaining half will be paid at the end of 2022.

•A $35 million decrease in energy center maintenance costs, other than those associated with the Callaway refueling and maintenance outage, at Ameren Missouri, primarily due to lower electric system infrastructure maintenance expenses as a result of decreased system load, disciplined cost management, and the deferral of projects to future periods.

•An $11 million decrease in coal inventory at Ameren Missouri primarily as a result of decreased market prices and inventory reductions at the coal-fired energy centers.

Ameren Missouri

Ameren Missouri’s cash provided by operating activities decreased $156 million in 2020, compared with 2019. The following items contributed to the decrease:

•A $190 million decrease resulting from reduced customer collections, primarily resulting from a decrease in sales volumes and an increase in accounts receivable balances, which were primarily due to the COVID-19 pandemic, and a net decrease attributable to regulatory recovery mechanisms, partially offset by decreased fuel and purchased power costs.

•A $38 million increase in payments to settle ARO liabilities, primarily related to CCR storage facilities.

•A $17 million decrease in net collateral activity with counterparties, primarily resulting from changes in the market prices of power and natural gas and changes in contracted commodity volumes.

•A $14 million increase in pension and postretirement benefit plan contributions.

•A $13 million increase in property tax payments due to higher assessed property tax values.

•A $12 million decrease, primarily resulting from increases to materials and supplies to support operations as levels were increased in 2020 to mitigate against any potential supply disruptions associated with the COVID-19 pandemic.

The following items partially offset the decrease in Ameren Missouri’s cash from operating activities between periods:

•A $76 million decrease in income tax payments to Ameren (parent) pursuant to the tax allocation agreement, primarily due to the timing of payments and lower taxable income in 2020.

•A $35 million decrease in energy center maintenance costs, other than those associated with the Callaway refueling and maintenance outage, primarily due to lower electric system infrastructure maintenance expenses as a result of decreased system load, disciplined cost management, and the deferral of projects to future periods.

•A $17 million decrease in payroll tax payments primarily due to the employer portion of Social Security taxes as a result of a payment deferral allowed under the Coronavirus Aid, Relief, and Economic Security Act. Half of this deferral will be paid at the end of 2021 and the remaining half will be paid at the end of 2022.

•An $11 million decrease in coal inventory primarily as a result of decreased market prices and inventory reductions at the coal-fired

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energy centers.

Ameren Illinois

Ameren Illinois’ cash provided by operating activities decreased $283 million in 2020, compared with 2019. The following items contributed to the decrease:

•A $195 million decrease resulting from reduced customer collections, primarily resulting from a decrease in sales volumes and an increase in accounts receivable balances, which were primarily due to the COVID-19 pandemic, and a net decrease attributable to regulatory recovery mechanisms, partially offset by decreased purchased power costs and volumes, and natural gas costs.

•A $37 million increase in income tax payments to Ameren (parent) pursuant to the tax allocation agreement, primarily due to the timing of payments in 2020.

•A $13 million decrease, primarily resulting from increases to materials and supplies to support operations as levels were increased in 2020 to mitigate against any potential supply disruptions associated with the COVID-19 pandemic.

•A $10 million increase in interest payments, primarily due to an increase in the average outstanding debt.

•A $10 million decrease in net collateral activity with counterparties, primarily resulting from changes in the market prices of power and natural gas, changes in contracted commodity volumes, and decreases resulting from renewable energy contracts entered into pursuant to the FEJA.

•Refunds paid in 2020 of $9 million associated with the November 2013 FERC complaint case, as discussed in Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report.

•A $8 million increase in pension and postretirement benefit plan contributions.

The decrease in Ameren Illinois’ cash from operating activities between periods was partially offset by a $14 million decrease in payroll tax payments primarily due to the employer portion of Social Security taxes as a result of a payment deferral allowed under the Coronavirus Aid, Relief, and Economic Security Act. Half of this deferral will be paid at the end of 2021 and the remaining half will be paid at the end of 2022.

Pension Plans

Ameren’s pension plans are funded in compliance with income tax regulations, federal funding requirements, and other regulatory requirements. As a result, Ameren expects to fund its pension plans at a level equal to the greater of the pension cost or the legally required minimum contribution. Based on Ameren’s assumptions at December 31, 2020, its investment performance in 2020, and its pension funding policy, Ameren expects to make aggregate contributions of $60 million over the next five years. We estimate that Ameren Missouri’s and Ameren Illinois’ portions of the future funding requirements will be approximately 30% and 60%, respectively. These estimates may change based on actual investment performance, changes in interest rates, changes in our assumptions, changes in government regulations, and any voluntary contributions. In 2020, Ameren contributed $52 million to its pension plans. See Note 10 – Retirement Benefits under Part II, Item 8, of this report for additional information.

Cash Flows from Investing Activities

Ameren’s cash used in investing activities increased $894 million during 2020, compared with 2019, primarily as a result of a $564 million increase from the acquisition of the High Prairie Renewable Energy Center and a $258 million increase in capital expenditures. Cash used in investing activities also increased due to a $45 million increase in net investment activity in the nuclear decommissioning trust fund at Ameren Missouri and a $35 million increase due to the timing of nuclear fuel expenditures. In addition to the capital expenditure changes at Ameren Missouri and Ameren Illinois discussed below, Ameren’s capital expenditures were partially offset by a $43 million decrease in capital expenditures at ATXI and other electric transmission subsidiaries, primarily as a result of decreased Mark Twain transmission line expenditures, as it was placed in service in 2019. In 2020, ATXI placed the ninth and final line segment of the Illinois Rivers transmission line in service.

Ameren Missouri’s cash used in investing activities increased $809 million during 2020, compared with 2019, primarily as a result of $564 million in cash paid for the acquisition of the High Prairie Renewable Energy Center and a $139 million increase in net money pool advances. Cash used in investing activities also increased due to a $45 million increase in net investment activity in the nuclear decommissioning trust fund, a $35 million increase due to the timing of nuclear fuel expenditures, and a $26 million increase in capital expenditures, primarily related to electric delivery infrastructure upgrades and electric transmission system reliability projects.

Ameren Illinois’ cash used in investing activities increased $239 million during 2020, compared with 2019, due to an increase in capital expenditures, primarily related to electric transmission system reliability projects.

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Capital Expenditures

The following charts present our capital expenditures for the years ended December 31, 2020 and 2019:

Ameren Illinois Electric Distribution Ameren Illinois Transmission

(a)Includes Other capital expenditures of $7 million and $(29) million for the years ended December 31, 2020 and 2019, respectively, which includes amounts for the elimination of intercompany transfers.

(b)Ameren Missouri capital expenditures include $564 million for the acquisition of the High Prairie Renewable Energy Center for the year ended December 31, 2020.

Ameren’s 2020 capital expenditures consisted of expenditures made by its subsidiaries, including ATXI and other electric transmission subsidiaries, which spent $113 million primarily on the Illinois Rivers transmission line. Of the $301 million in capital expenditures spent by Ameren Illinois Natural Gas during 2020, $189 million related to natural gas projects eligible for QIP recovery. In addition, Ameren Missouri expenditures included approximately $564 million for the acquisition of the High Prairie Renewable Energy Center. In both years, other capital expenditures were made principally to maintain, upgrade, and improve the reliability of the transmission and distribution systems of Ameren Missouri and Ameren Illinois by investing in substation upgrades, energy center projects, and smart-grid technology. Additionally, the Ameren Companies invested in various software projects.

Ameren’s 2019 capital expenditures consisted of expenditures made by its subsidiaries, including ATXI, which spent $156 million primarily on the Mark Twain and Illinois Rivers transmission lines. Of the $318 million in capital expenditures spent by Ameren Illinois Natural Gas during 2019, $203 million related to natural gas projects eligible for QIP recovery. Ameren Illinois exceeded the minimum capital spending levels required pursuant to IEIMA in 2019.

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The following table presents Ameren’s estimate of capital expenditures that will be incurred from 2021 through 2025, including construction expenditures, allowance for funds used during construction, and expenditures for compliance with existing environmental regulations:

ATXI and Other Electric Transmission Subsidiaries 55 130 – 140 185 – 195

Ameren Missouri’s estimated capital expenditures include transmission, distribution, grid modernization, and generation-related investments, as well as expenditures for compliance with environmental regulations. In addition, Ameren Missouri’s estimated capital expenditures include approximately $500 million related to 300 MWs of wind generation at the Atchison Renewable Energy Center, but exclude incremental renewable generation investment opportunities of 1,200 MWs by 2025, which are included in Ameren Missouri’s 2020 IRP. As of the date of this filing, no contractual agreements have been entered into, and no regulatory approvals have been requested, related to these opportunities. Ameren Illinois’ estimated capital expenditures are primarily for electric and natural gas transmission and distribution-related investments, including capital expenditures to modernize its electric and gas distribution systems. These planned investments are based on the assumption of continued constructive regulatory frameworks, including an assumption that Ameren Missouri requests and receives MoPSC approval of an extension of the PISA through December 2028.

Ameren Missouri continually reviews its generation portfolio and expected power needs. As a result, Ameren Missouri could modify its plan for generation capacity, the type of generation asset technology that will be employed, and whether capacity or power may be purchased, among other changes. Additionally, we continually review the reliability of our transmission and distribution systems, expected capacity needs, and opportunities for transmission investments within and outside our service territories. The timing and amount of investments could vary because of changes in expected capacity, the condition of transmission and distribution systems, and our ability and willingness to pursue transmission investments, among other factors. Any changes in future generation, transmission, or distribution needs could result in significant changes in capital expenditures or losses, which could be material. Compliance with environmental regulations could also have significant impacts on the level of capital expenditures.

Environmental Capital Expenditures

Ameren Missouri will continue to incur costs to comply with federal and state regulations, including those requiring the reduction of SO2, NOx, and mercury emissions from its coal-fired energy centers. See Note 14 – Commitments and Contingencies under Part II, Item 8, of this report for a discussion of existing and proposed environmental laws that affect, or may affect, our facilities and capital expenditures to comply with such laws.

Cash Flows from Financing Activities

Cash provided by, or used in, financing activities is a result of our financing needs, which depend on the level of cash provided by operating activities, the level of cash used in investing activities, the level of dividends, and our long-term debt maturities, among other things. As a result of capital market volatility, due, in part, to the COVID-19 pandemic, and to increase net available liquidity, Ameren (parent) accelerated a debt issuance to April 2020, which had been planned for later in 2020.

Ameren’s cash provided by financing activities increased $1,393 million during 2020, compared with 2019. During 2020, Ameren utilized net proceeds of $2,183 million from the issuance of long-term debt for general corporate purposes, including to repay then-outstanding short-term debt, including short-term debt incurred in connection with the repayment at maturity of long-term debt, to partially finance the acquisition of two wind generation facilities, and to repay other long-term debt. In addition, Ameren received cash proceeds of $425 million from the partial settlement of a forward sale agreement of common stock that were used to fund a portion of Ameren Missouri’s wind generation investments. Collectively, in 2020, Ameren repaid long-term debt of $442 million, received $50 million from net commercial paper issuances, and used cash provided by financing activities to fund, in part, investing activities. In comparison, in 2019, Ameren utilized net proceeds of $1,527 million from the issuance of long-term debt to repay then-outstanding short-term debt, including short-term debt incurred in connection with the repayment at maturity of long-term debt, and to repay at maturity other long-term debt. Collectively, in 2019, Ameren repaid long-term debt of $580 million, repaid net short-term debt of $157 million, and used cash provided by financing activities to fund, in part, investing activities. During 2020, Ameren paid common stock dividends of $494 million, compared with $472 million, in dividend payments in 2019.

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Ameren Missouri’s cash provided by financing activities increased $1,040 million during 2020, compared with 2019. During 2020, Ameren Missouri utilized net proceeds of $1,012 million from the issuance of long-term debt to repay then-outstanding short-term debt, including short-term debt incurred in connection with the repayment at maturity of long-term debt, and to partially finance the acquisition of two wind generation facilities. Collectively, in 2020, Ameren Missouri repaid long-term debt of $92 million, repaid net short-term debt of $234 million, and used cash provided by financing activities to fund, in part, investing activities. In comparison, in 2019, Ameren Missouri utilized net proceeds of $778 million from the issuance of long-term debt to repay then-outstanding short-term debt, including short-term debt incurred in connection with the repayment at maturity of long-term debt, and to repay at maturity other long-term debt. Collectively, in 2019, Ameren Missouri repaid long-term debt of $580 million, received $179 million from net commercial paper issuances, and used cash provided by financing activities to fund, in part, investing activities. During 2020, Ameren Missouri received $491 million in capital contributions from Ameren (parent), of which, $67 million was associated with the tax allocation agreement, compared with $124 million in capital contributions received in 2019. During 2020, Ameren Missouri paid common stock dividends of $66 million, compared with $430 million in dividend payments in 2019, due to an increase in investing cash needs, including the acquisition of wind generation facilities.

Ameren Illinois’ cash provided by financing activities increased $499 million during 2020, compared with 2019. During 2020, Ameren Illinois received $464 million in capital contributions from Ameren (parent), of which, $9 million was associated with the tax allocation agreement, compared with $15 million in capital contributions received in 2019. In addition, Ameren Illinois utilized net proceeds of $373 million from the issuance of long-term debt to repay then-outstanding short-term debt. Collectively, in 2020, Ameren Illinois repaid net short-term debt of $53 million, and used cash provided by financing activities to fund, in part, investing activities. In comparison, in 2019, Ameren Illinois utilized net proceeds of $299 million from the issuance of long-term debt to repay then-outstanding short-term debt. Collectively, in 2019 Ameren Illinois repaid net short-term debt of $19 million, and used cash provided by financing activities to fund, in part, investing activities. In addition, during 2020, Ameren Illinois borrowed $19 million from the money pool and paid common stock dividends of $9 million.

Credit Facility Borrowings and Liquidity

The liquidity needs of the Ameren Companies are typically supported through the use of available cash, drawings under committed credit agreements, commercial paper issuances, and/or, in the case of Ameren Missouri and Ameren Illinois, short-term affiliate borrowings. See Note 4 – Short-term Debt and Liquidity under Part II, Item 8, of this report for additional information on credit agreements, commercial paper issuances, Ameren’s money pool arrangements and related borrowings, and relevant interest rates.

The following table presents Ameren’s consolidated net available liquidity as of December 31, 2020:

Ameren (parent) and Ameren Missouri(a):

Missouri Credit Agreement – borrowing capacity $ 1,200

Less: Ameren (parent) commercial paper outstanding 315

Less: Letters of credit 3

Missouri Credit Agreement – subtotal 882

Ameren (parent) and Ameren Illinois(b):

Illinois Credit Agreement – borrowing capacity 1,100

Less: Ameren (parent) commercial paper outstanding 175

Less: Letters of credit 1

Illinois Credit Agreement – subtotal 924

Cash and cash equivalents 139

Net Available Liquidity $ 1,945

(a) The maximum aggregate amount available to Ameren (parent) and Ameren Missouri under the Missouri Credit Agreement is $900 million and $850 million, respectively. See Note 4 – Short-term Debt and Liquidity under Part II, Item 8, of this report for further discussion of the Credit Agreements.

(b) The maximum aggregate amount available to Ameren (parent) and Ameren Illinois under the Illinois Credit Agreement is $500 million and $800 million, respectively. See Note 4 – Short-term Debt and Liquidity under Part II, Item 8, of this report for further discussion of the Credit Agreements.

AEE US Equity

AEE · 10-K · period ended 2020-12-31

ITEM 1A. RISK FACTORS

ITEM 1B. UNRESOLVED STAFF COMMENTS

ITEM 2.PROPERTIES

ITEM 3.LEGAL PROCEEDINGS

ITEM 4.MINE SAFETY DISCLOSURES

ITEM 5.MARKET FOR REGISTRANTS’ COMMON EQUITY, RELATED STOCKHOLDER MATTERS, AND ISSUER PURCHASE OF EQUITY SECURITIES

ITEM 6.SELECTED FINANCIAL DATA

ITEM 7.MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

AEE US Equity☆

AEE · 10-K · period ended 2020-12-31

ITEM 1A. RISK FACTORS

ITEM 1B. UNRESOLVED STAFF COMMENTS

ITEM 2.PROPERTIES

ITEM 3.LEGAL PROCEEDINGS

ITEM 4.MINE SAFETY DISCLOSURES

ITEM 5.MARKET FOR REGISTRANTS’ COMMON EQUITY, RELATED STOCKHOLDER MATTERS, AND ISSUER PURCHASE OF EQUITY SECURITIES

ITEM 6.SELECTED FINANCIAL DATA

ITEM 7.MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

AEE US Equity