Trinseo PLC TSEOQ US Equity☆

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations

The following discussion summarizes the significant factors affecting the operating results, financial condition, liquidity and cash flows of our Company as of and for the periods presented below. The following discussion and analysis should be read in conjunction with the audited consolidated financial statements and the accompanying notes thereto, included elsewhere within this Annual Report. The statements in this discussion regarding industry outlook, our expectations regarding our future performance, liquidity and capital resources and all other non-historical statements in this discussion are forward-looking statements and are based on the beliefs of our management, as well as assumptions made by, and information currently available to, our management and are made as of the date of this Annual Report. See “Cautionary Note Regarding Forward-Looking Statements.” Actual results could differ materially from those discussed in or implied by forward-looking statements as a result of various factors, including those discussed below and elsewhere within this Annual Report, particularly in Item 1A—“Risk Factors.” Definitions of capitalized terms not defined herein appear in the notes to our consolidated financial statements.

2025 Highlights and Recent Developments

For the year ended December 31, 2025, we had net loss of $545.6 million, including $140.3 million of restructuring and other charges, and Adjusted EBITDA of $162.5 million. Adjusted EBITDA decreased compared to 2024 primarily due to lower volumes across all business segments and margin compression in Polymer Solutions and Latex Binders as a result of competitive price pressure particularly in Europe and Asia.

The Company continues to critically review its liquidity and anticipated capital requirements, including for service of the Company's debt. The consolidated financial statements have been prepared assuming that the Company will continue as a going concern. As of December 31, 2025, the Company had liquidity of $334.2 million and an accumulated deficit of $1,339.3 million and used cash in operations of $102.4 million during the year ended December 31, 2025. The Company expects continued operating losses and significant cash outflows from operating activities in the near term. Current macroeconomic and geopolitical conditions, including inflation, conflicts (such as the Russia-Ukraine war and military conflict in Iran), have created, and continue to create, significant uncertainty in operations, and weaker demand in many of our end markets, which have had, and are expected to continue to have, a material adverse effect on the Company's financial performance and liquidity forecasts.

The Company’s debt agreements include financial covenants, including a minimum liquidity requirement of $100.0 million under the 2028 Refinance Credit Agreement and additional liquidity‐related covenants under the OpCo

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Super‐Priority Revolver. Although the Company was in compliance with these covenants as of December 31, 2025, based on current forecasts, available borrowing capacity, and expected operating conditions, the Company believes it is unlikely to remain in compliance with these covenants for at least the twelve months following issuance of these financial statements. Failure to meet these covenant requirements in the future would cause the Company to be in default and could cause the maturity of the related debt to be accelerated and become immediately payable absent obtaining waivers from its lenders or negotiating amendments to avoid acceleration of its indebtedness. There can be no assurance that any such waivers or amendments would be available on acceptable terms or at all.

In February 2026 we entered into an amendment to the credit agreement governing our 2028 Term Loan B (the “Senior Credit Facility”), which extended the grace period for payment of interest due before March 1, 2026 until March 19, 2026, and elected to utilize the contractually-available grace periods for payment of interest on both the 2028 Term Loan B and our 2029 Refinance Senior Notes. These grace periods will both expire on March 19, 2026. A failure to make interest payments owed under the Senior Credit Facility or the 2029 Refinance Senior Notes indenture (the “2L Note Indenture”) at the end of the contractually-available grace periods would result in an event of default under these facilities, and also result in a cross-default under our 2028 Refinance Credit Facility, our Opco Super-Priority Revolver, and our accounts receivable securitization facility.

We expect to seek amendments to our Senior Credit Facility, our 2028 Refinance Credit Facility, our OpCo Super-Priority Revolver and our accounts receivable securitization facility to waive certain acceleration and collateral enforcement rights under such facilities following certain events of default or cross-defaults and to remove certain covenants and other provisions, prior to the end of the contractually-available grace periods. There can be no assurance that any such additional waivers or amendments would be available on acceptable terms or at all.

As a result of these factors, the Company has concluded that substantial doubt exists about its ability to continue as a going concern within one year after the date of issuance of these consolidated financial statements.

Financing and Liquidity Actions

In early 2025, we completed a series of refinancing transactions pursuant to a Transaction Support Agreement executed with key creditor groups. These actions extended our nearest debt maturity to 2028, improved operating liquidity, and reduced outstanding principal through an exchange of our 2029 senior notes. We issued approximately $380.0 million of new second-lien notes in exchange for substantially all of the existing 2029 notes, added a $115.0 million tranche under our 2028 term loan facility to retire the existing notes, and established a new $300.0 million super-priority revolving credit facility that replaced our prior revolver.

Polycarbonate Technology License Transaction

During 2025, we completed the delivery of a polycarbonate technology license and related production equipment under agreements valued at approximately $52.5 million. As a result, we recognized $27.4 million of income in the Polymer Solutions segment upon satisfying our performance obligations in 2025.

Strategic Operational Initiatives

In the fourth quarter of 2025, the Company, upon authorization from the Board of Directors, approved two restructuring plans to streamline our manufacturing footprint and exit underperforming assets. These actions include the planned closure of our MMA and ACH production sites in Italy and the closure of our polystyrene facility in Schkopau, Germany, with consolidation of remaining PS production in Belgium. Once fully implemented, these initiatives are expected to deliver roughly $30.0 million of annualized profitability improvements beginning in 2026.

Dividend Suspension

On October 3, 2025, the Company’s Board of Directors indefinitely suspended the quarterly dividend of $0.01 per share which is expected to save approximately $1.5 million annually.

New York Stock Exchange Delisting Notification

On March 2, 2026, we received written notice (the “Notice”) from the New York Stock Exchange (the “NYSE”) that the NYSE had determined to commence proceedings to delist the Company’s ordinary shares. Trading in our

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ordinary shares was suspended on February 27, 2026. As stated in the Notice, the NYSE reached its decision to delist the Company’s securities pursuant to Section 802.01B of the NYSE Listed Company Manual because the Company had fallen below the NYSE continued listing standard requiring listed companies to maintain an average market capitalization over a 30-trading day period of at least $15 million. The Company had previously received written notice from the NYSE on December 12, 2025 that it was no longer in compliance with Section 802.01B of the NYSE Listed Company Manual due to the fact that the Company’s average total market capitalization over a consecutive 30 trading-day period was less than $50 million and, at the same time, its stockholders’ equity was less than $50 million, and that it was also not in compliance with Section 802.01C of the NYSE Listed Company Manual because its average closing share price had fallen below $1.00 per share for 30 consecutive trading days. As stated in the Notice, the NYSE will file a Form 25 with the SEC to delist the Company’s ordinary shares from the NYSE. The delisting will be effective 10 days after the filing of the Form 25.

Exploration for Divestiture of Americas Styrenics

In March 2024, the Company announced it commenced a sale process for the Company’s interest in Americas Styrenics, via the initiation of an ownership exit provision in the joint venture agreement. Trinseo and Chevron Phillips Chemical Company LP, co-owners of Americas Styrenics, have decided to pursue a joint sale process. We, along with our partner, remain committed to sell Americas Styrenics, with our focus being to maximize value, given recent volatility in equity and debt markets, a signing may not occur until there are improvements in those underlying markets.

Results of Operations

Results of Operations for the Years Ended December 31, 2025, 2024, and 2023

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ Year Ended ​

​ ​ December 31, ​

(in millions) ​ ​ ​ 2025 ​ % ​ ​ ​ ​ 2024 ​ % ​ ​ ​ ​ ​ ​ 2023 ​ % ​

Impairment and other charges ​ ​ — ​ — % ​ ​ — ​ — % ​ ​ 349.5 ​ 10 %

Other expense (income), net ​ (25.2) ​ (1) % ​ 3.9 ​ — % ​ (17.2) ​ — %

Provision for income taxes ​ 42.6 ​ 1 % ​ 30.5 ​ 1 % ​ 68.4 ​ 2 %

2025 vs. 2024

Net Sales

Net sales decreased 15% compared to the prior year, reflecting a 10% reduction in sales volumes across all business segments due to continued weakness in end-market demand and a 6% decrease from lower pricing. These impacts were partially offset by a 1% benefit from favorable foreign currency exchange rates.

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Cost of Sales

Cost of Sales decreased 14% year-over-year primarily due to a 7% reduction from lower sales volumes and a 7% decrease due to lower pricing.

Gross Profit

The $99.7 million, or 38% decrease in gross profit was primarily due to margin compression in Polymer Solutions and Latex Binders from competitive price pressure particularly in Europe and Asia. See the segment discussion below for further information.

Selling, General and Administrative Expenses

SG&A expenses increased $90.0 million, or 28%, compared to the prior year. The increase was driven by $41.5 million of non-cash accelerated amortization of capitalized software assets related to the transition of our current ERP system to a cloud-based platform, $27.1 million of costs associated with the debt refinancing completed in the first quarter, $19.2 million of restructuring-related costs, $7.1 million reflecting prior-year pre-tax gains on asset sales that did not recur, and $4.6 million of higher spending on strategic initiatives. These increases were partially offset by a $9.5 million reduction in employee-related compensation accruals.

Equity in Earnings of Unconsolidated Affiliates

The decrease in equity earnings of $18.5 million was due to lower polystyrene volumes and higher raw material input costs, as well as unplanned outages during 2025.

Impairment and other charges

There were no impairment charges during the years ended December 31, 2025 and 2024. During the year ended December 31, 2023, the Company recorded a non-cash goodwill impairment charge of $349.0 million related to the Engineered Materials reporting unit, as described within Note 14 in the consolidated financial statements. The Company also recorded impairment charges of $0.5 million related to the Boehlen styrene monomer assets during the year ended December 31, 2023, as described within Note 18 in the consolidated financial statements.

Interest Expense, Net

The increase in interest expense, net of $6.3 million, or 2%, was primarily attributable to the increased year-over-year usage of our short-term borrowings under the Accounts Receivable Securitization Facility and the OpCo Super-Priority Revolver as well as the additional interest margin incurred from payment in kind elections (“PIK Interest Election”) during 2025. These increases were partially offset by a decrease in market interest rates on our variable rate debt, specifically the 2028 Term Loan B. Refer to Note 16 in the condensed consolidated financial statements for further information.

Loss on Extinguishment of Long-Term Debt

Loss on extinguishment of long-term debt was $0.2 million for the year ended December 31, 2025, this is comprised entirely of the write-off of unamortized deferred financing costs due to the Company redeeming the 2025 Senior Notes in January 2025, in which the notes were cancelled and the related indenture was satisfied and discharged.

Loss on extinguishment of long-term debt was $0.6 million for the year ended December 31, 2024, this is comprised entirely of the write-off of unamortized deferred financing costs due to the Company terminating the 2010 A/R Facility in July 2024 and paying the outstanding amount in full.

Other Expense (Income), Net

Other income, net for the year ended December 31, 2025 was $25.2 million. Other income, net was primarily comprised of $27.4 million of license income for polycarbonate technology. This was partially offset by $0.3 million of foreign exchange translation gains, which included $27.6 million of foreign exchange transaction gains primarily from

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the remeasurement of our euro denominated payables due to the relative change in rates between the U.S. dollar and the euro during the period, offset by $27.3 million of losses from our foreign exchange forward contracts.

Other expense, net for the year ended December 31, 2024 was $3.9 million. Other expense, net was comprised of foreign exchange transaction losses of $1.7 million, which included $19.5 million of foreign exchange transaction losses primarily from the remeasurement of our euro denominated payables due to the relative changes in rates between the U.S. dollar and the euro during the period, partially offset by $17.8 million of gains from our foreign exchange forward contracts.

Provision for Income Taxes

Provision for income taxes was $42.6 million and $30.5 million for the years ended December 31, 2025 and 2024, respectively, which resulted in an effective tax rate of (8)% and (10)%, respectively. The increase in provision for income taxes in 2025 was primarily driven by the increase in valuation allowance in France, Germany and the Netherlands, as well as the geographical mix of earnings, partially offset by the increase in valuation allowance in China in 2024.

Selected Segment Information

The Company’s reportable segments are as follows: Engineered Materials, Latex Binders, Polymer Solutions, and Americas Styrenics. Refer to Item 1—Business for a description of our segments, including a detailed overview, products and end uses, and competition and customers.

The following sections present net sales, Adjusted EBITDA, and Adjusted EBITDA margin by segment for the years ended December 31, 2025, 2024, and 2023. Inter-segment sales have been eliminated. Refer to Note 23 in the consolidated financial statements for a detailed definition of Adjusted EBITDA and a reconciliation of income from continuing operations before income taxes to segment Adjusted EBITDA.

Engineered Materials Segment

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ Year Ended ​ ​ ​ ​

​ ​ December 31, ​ ​ Percentage Change ​

Adjusted EBITDA margin ​ 11 % ​ 9 % ​ 4 % ​ ​ ​ ​ ​

2025 vs. 2024

The 8% decrease in net sales was attributable to an 8% decrease due to lower sales volumes from PMMA Resins, Rigid Compounds, and MMA.

Adjusted EBITDA increased $14.8 million, of which $29.8 million was due to higher margins resulting from mix improvements, $14.0 million was from lower fixed costs, $0.6 million was from favorable currency impacts, and $0.4 million was from favorable foreign exchange rate impacts. These increases were partially offset by a $30.0 million decrease due to the lower sales volumes from PMMA Resins, Rigid Compounds, and MMA.

Latex Binders Segment

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ Year Ended ​ ​ ​ ​

​ ​ December 31, ​ ​ Percentage Change ​

Adjusted EBITDA margin ​ 9 % ​ 10 % ​ 9 % ​ ​ ​ ​ ​

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2025 vs. 2024

The 17% decrease in net sales was primarily due to a 11% decrease due to lower sales volumes in paper and board and textile applications in Europe and a 7% decrease from lower price from the pass-through of lower raw material costs. These decreases were partially offset by a 1% increase from favorable foreign exchange rate impacts.

The $28.3 million, or 30%, decrease in Adjusted EBITDA was primarily due to a $28.8 million, or 30%, decrease due to lower sales volumes and a $10.0 million decrease from lower margins. These decreases were partially offset by a $9.3 million increase from lower fixed costs, a $0.8 million increase from favorable foreign exchange rate impacts, and a $0.4 million increase from favorable currency impacts.

Polymer Solutions Segment

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ Year Ended ​ ​ ​ ​

​ ​ December 31, ​ ​ Percentage Change ​

Adjusted EBITDA margin ​ 6 % ​ 6 % ​ 3 % ​ ​ ​ ​ ​

2025 vs. 2024

Net sales decreased 20% year-over-year, driven by an 11% decline in sales volumes and a 10% decrease from lower pricing due to unfavorable product mix. These impacts were partially offset by a 1% benefit from favorable foreign currency exchange rates.

The $16.8 million, or 20%, decrease in Adjusted EBITDA was primarily due to a $56.2 million, or 66%, decrease due to lower sales volume and a $39.7 million, or 46%, decrease due to lower margins. These decreases were partially offset by a $50.7 million, or 59%, increase from lower fixed costs from the exit of styrene production, a $27.4 million, or 32% increase from polycarbonate technology licensing income, and a $0.8 million, or 1%, increase from favorable foreign exchange rate impacts.

Americas Styrenics Segment

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ Year Ended ​ ​ ​ ​

​ ​ December 31, ​ ​ Percentage Change ​

Adjusted EBITDA* ​ $ (3.1) ​ ​ $ 15.4 ​ ​ $ 62.1 ​ ​ (120) % (75) %

*The results of this segment are comprised entirely of earnings from Americas Styrenics, our equity method investment. As such, Adjusted EBITDA related to this segment is included within “Equity in earnings of unconsolidated affiliates” in the consolidated statements of operations.

2025 vs. 2024

The decrease in Adjusted EBITDA was mainly due to a costs associated with unplanned outages in the second and third quarter at its styrene production facility, lower polystyrene volumes, as well as lower margins from higher raw material input costs.

Outlook

The Company is expecting a delay in demand recovery and lower cumulative growth than previously expected. Geopolitical events continue to disproportionally impact European chemical producers and the Chinese chemical industry continues to benefit from low-cost Russian crude, which enables lower downstream pricing. Because of these market factors, including the delay in demand recovery, 2026 demand will likely be similar to 2025. However, the proactive management actions taken to exit underperforming assets in 2025 are expected to result in improved operational results for the Company.

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The Company continues to execute on cash management and strategic operational plans to manage liquidity and debt covenant compliance, including evaluating contractual obligations and productivity initiatives to manage operating expenses. Additionally, as previously disclosed, the Company is engaged in ongoing discussions with its financial stakeholders regarding its capital structure to evaluate and execute potential strategic alternatives to our existing capital structure including modification of the terms of our outstanding indebtedness. The Company is unable to predict, with certainty, the impact that the current macroeconomic conditions will have on its ability to consummate these potential transactions or maintain compliance with the financial covenants contained in the Company's debt agreements.

Non-GAAP Performance Measures

We present Adjusted EBITDA as a non-GAAP financial performance measure, which we define as income from continuing operations before interest expense, net; provision for income taxes; depreciation and amortization expense; loss on extinguishment of long-term debt; asset impairment charges; gains or losses on the dispositions of businesses and assets; restructuring charges; acquisition related costs and other items. In doing so, we are providing management, investors, and credit rating agencies with an indicator of our ongoing performance and business trends, removing the impact of transactions and events that we would not consider a part of our core operations.

There are limitations to using financial performance measures such as Adjusted EBITDA. This performance measure is not intended to represent net income or other measures of financial performance. As such, it should not be used as an alternative to net income as an indicator of operating performance. Other companies in our industry may define Adjusted EBITDA differently than we do. As a result, it may be difficult to use this or similarly-named financial measures that other companies may use to compare the performance of those companies to our performance. We compensate for these limitations by providing a reconciliation of this performance measure to our net income, which is determined in accordance with accounting principles generally accepted in the United States of America (“GAAP”).

Adjusted EBITDA is calculated as follows for the years ended December 31, 2025, 2024, and 2023. For discussion related to 2023 activity, refer to the Company’s Form 10-K filed on February 27, 2025.

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ Year Ended ​

​ ​ December 31,

Provision for income taxes ​ 42.6 ​ 30.5 ​ 68.4 ​

Loss on financing transactions(c) ​ ​ 26.5 ​ ​ — ​ — ​

Net gain on disposition of businesses and assets(d) ​ ​ — ​ ​ (7.1) ​ (25.6) ​

Restructuring and other charges(e) ​ ​ 63.9 ​ ​ 44.7 ​ 31.4 ​

Acquisition transaction and integration net costs(f) ​ ​ — ​ ​ — ​ ​ (1.4) ​

Asset impairment charges or write-offs(g) ​ ​ — ​ ​ — ​ ​ 2.7 ​

Goodwill impairment charges(h) ​ ​ — ​ ​ — ​ ​ 349.0 ​

Other items(i) ​ ​ 9.7 ​ ​ 6.4 ​ 21.5 ​

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Note that the accelerated depreciation charges incurred as part of both the Company’s asset restructuring plan and corporate restructuring program are included within the “Depreciation and amortization” caption above and therefore are not included as a separate adjustment within this caption.

Other items for the years ended December 31, 2024 and 2023 primarily relate to third party fees incurred in conjunction with certain of the Company’s strategic initiatives, including the ERP upgrade project.

Liquidity and Capital Resources

Capital Resources, Indebtedness and Liquidity

We require cash primarily to fund day-to-day operations, capital investments and other strategic initiatives, purchase raw materials, and service our outstanding debt obligations. Our liquidity is generated from cash on hand, cash flows from continuing operations, and borrowing availability under the OpCo Super-Priority Revolver and the Accounts Receivable Securitization Facility.

The 2028 Refinance Credit Agreement includes customary affirmative, negative, and financial covenants, with events of default that include (i) a change of control, (ii) failure to maintain at least $100.0 million of Liquidity at each month-end, and (iii) a cross-default to the Credit Agreement. If a default occurs, the Term Lenders may accelerate amounts due under the 2028 Refinance Term Loans. Liquidity, as defined consistently under both the OpCo Super-Priority Revolver and the 2028 Refinance Credit Agreement, includes cash and cash equivalents held by certain restricted subsidiaries and available borrowing capacity under both facilities, subject to terms in the 2028 Refinance Credit Agreement.

The OpCo Super-Priority Revolver also includes an anti-cash hoarding provision requiring repayment of borrowings to the extent cash and cash equivalents on the 15th of each month exceed $100.0 million at loan parties or $50.0 million at nonloan parties. The OpCo Super-Priority Revolver also features a springing covenant which applies when 30% or more of the OpCo Super-Priority Revolver’s capacity is drawn which then requires the Company to meet a superpriority lien net leverage ratio (as defined in the secured credit agreement) not to exceed 1.50:1.00 at the end of each financial quarter. As of December 31, 2025, the outstanding borrowings, inclusive of certain letters of credit, did

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exceed the 30% threshold, however the superpriority lien net leverage ratio was below the 1.50x threshold, (0.38):1.00. As of December 31, 2025, the Company was in compliance with all covenants in its debt agreements.

As of December 31, 2025, we had total Liquidity of $334.2 million, consisting of $139.4 million of cash and cash equivalents and $194.8 million of borrowing availability under the 2026 Revolving Facility and the Accounts Receivable Securitization Facility ($191.6 million and $3.2 million, respectively). We had $2,591.4 million of outstanding indebtedness as of December 31, 2025, compared to $2,448.4 million at December 31, 2024, and working capital of $150.0 million and $267.3 million at those respective dates. Of our cash, $89.6 million and $107.7 million, respectively, was held outside Ireland (our country of domicile), all of which is readily convertible into other currencies including U.S. dollars. Because we do not intend to indefinitely reinvest foreign cash, we record deferred tax liabilities on unremitted earnings. Additional information about our debt, rates, and maturities is provided in Note 16 to the consolidated financial statements.

Potential Restructuring of Our Indebtedness

We have been reviewing a number of potential alternatives regarding our outstanding indebtedness. These alternatives include refinancings, exchange offers, consent solicitations, the issuance of new indebtedness, amendments to the terms of our existing indebtedness and/or other transactions. We are currently in active discussions with holders of our indebtedness and have engaged outside advisors with respect to these alternatives. Additionally, the Company has appointed two new board members with significant experience in debt restructuring and strategic transactions.

Among these alternatives is a restructuring that would, on a consensual basis, seek to modify the terms of substantially all of our outstanding indebtedness, potentially through an in-court or out-of-court process. We may offer to exchange the indebtedness under our 2028 Refinance Term Loans, 2028 Term Loan B, or 2029 Refinance Senior Notes for new debt and/or equity securities of our parent and/or subsidiary companies. In conjunction with any such transactions, we may seek consents to amend the documents governing our indebtedness to amend or eliminate certain covenants or collateral provisions. Because the terms of any such transactions will be subject to negotiations with the holders of our indebtedness, they may differ materially from those described above and are, to a large extent, outside of our control. There can be no assurance that we will be able to complete any such transactions, and, as no decision with respect to the terms of any such transactions has been made, we may decide not to pursue any such transactions. If we are unable or elect not to complete any such transactions, or if the Company is unable to obtain necessary waivers or amendments and its debt is accelerated, there can be no assurance that the Company would be able to obtain replacement financing or to satisfy its obligations, in which case the Company may pursue a process to restructure its indebtedness, through an in-court or out-of-court process. We continue to focus on our initiatives to drive operational performance, maintain safe manufacturing processes, retain talent in our organization and continue our objective to become a specialties materials provider.

The accompanying consolidated financial statements have been prepared on a going concern basis, which contemplates realization of assets and satisfaction of liabilities in the ordinary course of business. As such, they do not include any adjustments to the recoverability and reclassification of recorded amounts that might be necessary should the Company be unable to continue as a going concern. Refer to Note 16 and Item 1A— Risk Factors, for additional information.

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DebtOverview

The table below summarizes our outstanding indebtedness as of December 31, 2025 and 2024, including related interest expense and effective interest rates:

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ As of and for the Year Ended ​ As of and for the Year Ended

​ ​ ​ ​ Effective ​ ​ ​ ​ ​ Effective ​ ​

​ ​ ​ ​ Interest ​ Interest ​ ​ ​ Interest ​ Interest

2029 Refinance Senior Notes ​ $ 441.6 ​ 5.0 % $ 20.4 ​ $ — ​ — % $ —

Senior Credit Facility ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

OpCo Super-Priority Revolver ​ ​ 75.0 ​ 6.9 % ​ 5.8 ​ ​ — ​ — % ​ —

2026 Revolving Facility ​ ​ — ​ — % ​ — ​ ​ — ​ — % ​ 2.9

As of December 31, 2025, our Senior Credit Facility—comprising the OpCo Super-Priority Revolver—had a total capacity of $300.0 million, with $191.6 million available after considering $33.4 million in letters of credit. Unused commitments incur a quarterly fee of 0.375% per annum.

The 2028 Term Loan B (original principal $750.0 million, maturing May 2028) requires quarterly amortization of 0.25% of original principal and bears interest at SOFR + 2.50% (0.00% floor). During 2025, we made $7.5 million in net principal payments and have an additional $7.5 million due within one year.

The 2028 Refinance Term Loans bear interest at Term SOFR + 8.50% (3.00% SOFR floor) and were issued with a 3% original issue discount. In 2025, we made $11.3 million in net principal payments, with $11.3 million classified as current. Through September 8, 2025, we were permitted to elect PIK interest, and during 2025 we deferred $39.6 million of interest, resulting in $48.1 million capitalized to principal.

Our second-lien 2029 Refinance Senior Notes include $379.5 million of 7.625% notes maturing May 3, 2029. Interest is payable semi-annually. Under the 2L Note Indenture, we elected PIK interest on 2.50% of interest during 2025, deferring $9.1 million.

We maintain an Accounts Receivable Securitization Facility maturing January 2028 with an optional one-year extension. The facility allows up to $150.0 million of borrowings and carries a minimum interest charge on $75.0 million regardless of actual borrowings. As of December 31, 2025, $118.0 million was outstanding, supported by $121.2 million of eligible receivables, leaving $3.2 million of availability.

During 2025, the remaining 2025 Senior Notes were redeemed, and the 2029 Senior Notes were exchanged or redeemed in conjunction with the issuance of the 2029 Refinance Senior Notes, resulting in the satisfaction and discharge of both related indentures.

Additional Considerations

Our debt costs and access to capital depend on credit ratings and leverage/coverage metrics. We may also opportunistically repurchase or retire debt based on market conditions and liquidity needs. On November 27, 2025, S&P Global Ratings downgraded the Company’s issuer credit rating to ‘CCC’ and, on March 3, 2026, further downgraded the credit rating to ‘SD’. The ratings agency also highlighted the Company’s heightened refinancing risk associated with its 2028 maturities and the potential for further downward rating actions if liquidity deteriorates or if end-market conditions do not materially improve over the next twelve months. Moody’s outlook remained stable, maintaining their Caa2 rating.

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The borrowers and issuers of our debt depend on upstream cash flows from subsidiaries. Although no material restrictions currently exist, jurisdictional regulations may introduce future constraints. The Senior Credit Facility, Refinance Credit Agreement, and 2L Note Indenture restrict dividends to Trinseo PLC. In 2025, we declared dividends of $0.8 million before the Board elected to suspend future dividends.

Macroeconomic conditions—including tariff uncertainty, higher interest rates, and geopolitical factors—have negatively impacted demand, earnings, and liquidity. We have experienced recurring net losses and negative operating cash flows and expect to remain unprofitable in the near term.

We do not have any off-balance-sheet arrangements that are expected to have a material effect on our financial condition or liquidity.

Cash Flows

The table below summarizes our primary sources and uses of cash for the years ended December 31, 2025, 2024, and 2023. We have derived the summarized cash flow information from our audited financial statements. Refer to the Company’s Form 10-K filed on February 27, 2025 for discussion related to 2023.

​

​ ​ ​ ​ ​ ​ ​

​ ​ Year Ended

​ ​ December 31,

Net cash provided by (used in): ​ ​ ​ ​ ​ ​

Operating activities ​ $ (102.4) ​ $ (14.2)

Investing activities ​ ​ (41.0) ​ ​ (55.1)

Financing activities ​ 73.5 ​ 26.4

Effect of exchange rates on cash ​ 7.0 ​ (6.3)

Net change in cash, cash equivalents, and restricted cash ​ $ (62.9) ​ $ (49.2)

Operating Activities

Net cash used in operating activities during the year ended December 31, 2025 totaled $102.4 million, which included a$97.1 million decrease in working capital and the impact of $26.3 million in expenses related to refinancing that were not eligible for capitalization as deferred financing costs.

Net cash used in operating activities during the year ended December 31, 2024 totaled $14.2 million, which included a $123.7 million decrease in working capital, principally related to continued inventory management actions and cash collections, $45.0 million of dividends received from Americas Styrenics and $33.9 million in deferred interest cash payments via the PIK Interest Election.

Investing Activities

Net cash used in investing activities during the year ended December 31, 2025 totaled $41.0 million, which was primarily attributable to capital expenditures of $51.0 million offset by proceeds from the sale of business and other assets of $10.0 million. During 2025, the Company continued to proactively reduce or defer capital expenditures during the year to preserve liquidity.

Capital expenditures for 2026 are expected to be similar to 2025, approximately $51.0 million, inclusive of spending for both compliance and maintenance costs, and growth initiatives, including material substitution applications as well as products containing recycled or bio-based materials.

Net cash used in investing activities during the year ended December 31, 2024 totaled $55.1 million, which was primarily attributable to capital expenditures of $63.3 million offset by proceeds from the sale of business and other assets of $8.2 million.

Financing Activities

Net cash provided by financing activities during the year ended December 31, 2025 totaled $73.5 million. During the year, the Company drew $265.0 million and $145.0 million in proceeds and repaid $190.0 million and $102.0 million

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from the A/R Facility and OpCo Super-Priority Revolver, respectively, principally related to funding working capital and other requirements. This activity also included the issuance of additional 2028 Refinance Term Loans ($115.0 million of aggregate principal) in exchange for the redemption of the 2025 Senior Notes ($115.0 million reduction in aggregate principal), $19.8 million in debt issuance costs that met the criteria for deferred financing charges, $19.4 million in debt repayments, $1.2 million of dividends paid, and $3.4 million of net repayments of short-term borrowings.

Net cash provided by financing activities during the year ended December 31, 2024 totaled $26.4 million. During the year, the Company drew $513.2 million in proceeds from the A/R Facility, and repaid $438.2 million, principally related to funding working capital and other requirements. This activity was partially offset by $18.3 million in debt repayments, $1.7 million of dividends paid, and $19.3 million of net repayments of short-term borrowings.

Free Cash Flow

We use Free Cash Flow as a non-GAAP measure to evaluate and discuss the Company’s liquidity position and results. Free Cash Flow is defined as cash from operating activities, less capital expenditures. We believe that Free Cash Flow provides an indicator of the Company’s ongoing ability to generate cash through core operations, as it excludes the cash impacts of various financing transactions as well as cash flows from business combinations that are not considered organic in nature. We also believe that Free Cash Flow provides management and investors with useful analytical indicator of our ability to service our indebtedness, pay dividends (when declared), and meet our ongoing cash obligations.

Free Cash Flow is not intended to represent cash flows from operations as defined by GAAP, and therefore, should not be used as an alternative for that measure. Other companies in our industry may define Free Cash Flow differently than we do. As a result, it may be difficult to use this or similarly-named financial measures that other companies may use to compare the liquidity and cash generation of those companies to our own. We compensate for these limitations by providing a reconciliation to cash provided by operating activities, which is determined in accordance with GAAP.

​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ Year Ended

​ ​ December 31,

Cash provided by (used in) operating activities ​ $ (102.4) ​ $ (14.2) ​ $ 148.7

Capital expenditures ​ ​ (51.0) ​ ​ (63.3) ​ ​ (69.7)

Refer to the discussion above for significant impacts to cash provided by operating activities for the years ended December 31, 2025 and 2024. Refer to the Company’s Form 10-K filed on February 27, 2025 for discussion related to 2023.

​

Contractual Obligations and Commercial Commitments

The Company’s primary contractual obligations and commercial commitments consist of the payments for principal and interest on our outstanding long-term debt, raw material purchases, funding requirements under our pension and other postretirement benefits, lease commitments, and obligations under our SAR SSAs.

The Company has both fixed and variable-rate long-term debt arrangements, which have varying principal and interest payment requirements over their contractual terms. Refer to the table and section above as well as to Note 16 in the consolidated financial statements for more information on our debt arrangements. Additionally, refer to Item 7A—Quantitative and Qualitative Disclosures about Market Risk for discussion of our interest rate and foreign currency risks related to our debt and debt-related hedging arrangements.

The Company has certain raw material purchase contracts where we are required to purchase certain minimum volumes at prevailing market prices. As of December 31, 2025, the Company had $694.0 million of raw material purchase obligations, of which $219.7 million is due within the next twelve months. These commitments have remaining terms ranging from one to five years. Refer to Note 19 in the consolidated financial statements for more information on

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raw material purchase commitments. Additionally, refer to Item 1 – Business – Sources and Availability of Raw Materials for further description of the sources of our key raw materials.

The Company has various pension and other postretirement plans. The Company is required to make minimum contributions to certain of our funded pension plans and is also obligated to make benefit payments to employees for the unfunded pension plans and other postretirement plans. As of December 31, 2025, the Company’s estimated future benefit payments through 2035, reflecting expected future service, as appropriate, was $154.1 million, of which $14.4 million is due within the next twelve months. Refer to the section of our Critical Accounting Policies and Estimates entitled “Pension Plans and Postretirement Benefits” for more information on the factors impacting our pension and postretirement costs. Additionally, refer to Note 21 in the consolidated financial statements for more details on these employee benefit plans and the future payments expected to be made for them through 2034.

The Company has operating and finance leases for certain of its plant and warehouse sites, office spaces, rail cars, storage facilities, and equipment. The Company’s leases have remaining terms of one month through eleven years. As of December 31, 2025, the Company’s estimated minimum commitments related to our finance and operating lease obligations was $83.1 million, of which $16.8 million is due within the next twelve months. Refer to Note 20 in the consolidated financial statements for further information on our lease portfolio and future lease obligations.

As described in Item 1— Business— Our Relationship with Dow, the Company is party to SAR SSAs with Dow, which are agreements under which Dow provides certain site services to the Company at Dow-owned locations. Based on our current year known costs and assuming that we continue with the SAR SSAs with similar annualized costs going forward, we estimate our contractual obligations under these agreements to be approximately $17.5 million annually for 2025 through 2029, and a total of $108.5 million thereafter through June 2041. Refer to the aforementioned section of Item 1 for more information regarding these agreements, including details regarding the rights of the Company and Dow to terminate said agreements.

Derivative Instruments

The Company’s ongoing business operations expose it to various risks, including fluctuating foreign exchange rates, interest rate risk, and commodity price risk. To manage this risk, the Company periodically enters into derivative financial instruments, such as foreign exchange forward contracts, interest rate swap agreements, and commodity swap agreements. A summary of these derivative financial instrument programs is described below; however, refer to Note 17 of the consolidated financial statements for further information. The Company does not hold or enter into financial instruments for trading or speculative purposes.

Foreign Exchange Forward Contracts

Certain subsidiaries have assets and liabilities denominated in currencies other than their respective functional currencies, which creates foreign exchange risk. Our principal strategy in managing exposure to changes in foreign currency exchange rates is to naturally hedge the foreign currency-denominated liabilities on our consolidated balance sheets against corresponding assets of the same currency such that any changes in liabilities due to fluctuations in exchange rates are offset by changes in their corresponding foreign currency assets. In order to further reduce our exposure, the Company uses foreign exchange forward contracts to economically hedge the impact of the variability in exchange rates on our assets and liabilities denominated in certain foreign currencies. These derivative contracts are not designated for hedge accounting treatment.

Foreign Exchange Cash Flow Hedges

The Company also enters into forward contracts with the objective of managing the currency risk associated with forecasted U.S. dollar-denominated raw materials purchases by one of our subsidiaries whose functional currency is the euro. By entering into these forward contracts, which are designated as cash flow hedges, the Company buys a designated amount of U.S. dollars and sells euros at the prevailing market rate to mitigate the risk associated with the fluctuations in the euro-to-U.S. dollar foreign currency exchange rate.

Commodity Cash Flow Hedges & Commodity Economic Hedges

The Company purchased certain commodities, primarily natural gas, to operate facilities and generate heat and steam for various manufacturing processes, which are subject to price volatility. In order to manage the risk of price

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fluctuations associated with these commodity purchases, as deemed appropriate, the Company may enter into commodity swaps agreements or option contracts. Under these derivative contracts, the Company is effectively converting a portion of our natural gas costs into a fixed rate obligation to mitigate the risk of price fluctuations associated with the underlying commodity purchases. Certain of these commodity swaps were designated as cash flow hedges (“commodity cash flow hedges”), and the remaining commodity swaps were not designated for hedge accounting treatment (“commodity economic hedges”). The Company does not have any outstanding commodity cash flow or economic agreements as of December 31, 2025.

Critical Accounting Policies and Estimates

Our discussion and analysis of results of operations and financial condition are based upon our financial statements, which have been prepared in accordance with GAAP. The preparation of these financial statements requires us to make estimates and judgments that affect the amounts reported. We base these estimates and judgments on historical experiences and assumptions believed to be reasonable under the circumstances. Actual results could vary from our estimates under different conditions. Our significant accounting policies, which may be affected by our estimates and assumptions, are more fully described in Note 2 in the consolidated financial statements. An accounting policy is deemed to be critical if it requires an accounting estimate to be made based on assumptions about matters that are highly uncertain at the time the estimate is made, and if different estimates that reasonably could have been used, or changes in the accounting estimates that are reasonably likely to occur periodically, could materially impact the financial statements. The following critical accounting policies reflect our most significant estimates and assumptions used in the preparation of the consolidated financial statements.

Valuation of Assets and Impairment Considerations

Valuation of Assets

Acquisitions that qualify as a business combination are accounted for using the purchase accounting method. Amounts paid for an acquisition are allocated to the assets acquired and liabilities assumed based on their fair value as of the date of acquisition. Goodwill is recorded as the difference between the fair value of the acquired assets and liabilities assumed (net assets acquired) and the purchase price. Goodwill is not amortized, but is reviewed for impairment annually as of October 1, or when events or changes in the business environment indicate that the carrying value of a reporting unit may exceed its fair value. Refer to the discussion below for further information on asset impairments.

Specifically, the calculation of the fair value of tangible assets, including property, plant and equipment, typically utilize the cost approach, which computes the cost to replace the asset, less accrued depreciation resulting from physical deterioration and functional and external obsolescence. The calculation of the fair value of identified intangible assets is determined using cash flow models following the income and cost approaches (or some combination thereof). Significant inputs include estimated future cash flows, discount rates, royalty rates, growth rates, sales projections, customer retention rates, and terminal values, all of which require significant management judgment. Definite-lived intangible assets, which are primarily comprised of customer relationships, developed technology, tradenames, and software, are amortized over their estimated useful lives using the straight-line method and are assessed for impairment whenever events or changes in circumstances indicate the carrying value of the asset may not be recoverable.

Impairment Considerations

As of December 31, 2025, net property, plant and equipment, net identifiable finite-lived intangible assets, and goodwill totaled $523.6 million, $492.9 million, and $67.7 million, respectively. Management makes estimates and assumptions in preparing the consolidated financial statements for which actual results will emerge over long periods of time. This includes the recoverability of long-lived assets employed in the business. These estimates and assumptions are closely monitored by management and periodically adjusted as circumstances warrant. For instance, expected asset lives may be shortened or impairment may be recorded based on a change in the expected use of the asset or performance of the related asset group.

We evaluate long-lived assets and identifiable finite-lived intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset grouping may not be recoverable. In the event the carrying value of the asset exceeds its undiscounted future cash flows and the carrying value is not considered

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recoverable, impairment may exist. An impairment loss, if any, is measured as the excess of the asset’s carrying value over its fair value, generally based on a discounted future cash flow method, independent appraisals, etc.

In connection with our strategy to focus efforts and increase investments in certain product offerings serving specific applications that are less cyclical and offer significantly higher growth and margin potential, and other management considerations, in March of 2020, the Company initiated a consultation process with the Economic Council and Works Councils of Trinseo Deutschland regarding the disposition of our styrene monomer assets in Boehlen, Germany. The Company’s assessments of these long-lived asset groups for impairment indicated that the carrying values of the asset groups at each location were not recoverable when compared to the expected undiscounted future cash flows from the operation and potential disposition of these assets. The fair value of the depreciable assets at each location was determined through an analysis of the underlying fixed asset records in conjunction with the use of industry experience and available market data. Based on the Company’s assessments, for the year ended December 31, 2023, we recorded impairment charges on the Boehlen styrene monomer assets of $0.5 million, which include charges recorded subsequent to March 2020 related to capital expenditures at the facility that we determined to be impaired. The amounts are included within “Impairment and other charges” in the consolidated statements of operations. Refer to Note 18 for more information.

Long-lived assets to be disposed of by sale are classified as held-for-sale and are reported at the lower of carrying amount or fair value less cost to sell, and depreciation is ceased. Long-lived assets to be disposed of in a manner other than by sale are classified as held-and-used until they are disposed. The Company had no material assets classified as held-for-sale as of December 31, 2025.

As noted above, our goodwill impairment testing is performed annually as of October 1 at a reporting unit level. We perform more frequent impairment tests when events or changes in circumstances indicate that the fair value of a reporting unit has more likely than not declined below the carrying value.

A goodwill impairment loss generally would be recognized when the carrying amount of the reporting unit’s net assets exceeds the estimated fair value of the reporting unit. When supportable, the Company employs the qualitative assessment of goodwill impairment prescribed by Accounting Standards Codification 350. Otherwise, the estimated fair value of a reporting unit is primarily determined using an income approach (under the discounted cash flow method). Key assumptions and estimates used in the goodwill impairment testing include projections of revenues and EBITDA, the estimated weighted average cost of capital (“WACC”), and a projected long-term growth rate, all of which are based on data available at the time of the testing. The WACC is calculated incorporating weighted average returns on debt and equity from similar market participants, and therefore, changes in the market, which are beyond the control of the Company, may have an impact on future calculations of estimated fair value.

As of January 1, 2023, the Company realigned the Engineered Materials segment reporting structure. The PMMA business and Aristech Surfaces reporting units were combined with the Legacy Engineered Materials reporting unit to form the Engineered Materials reporting unit. Impairment assessments on each reporting unit were performed immediately before and after the change in organizational structure where it was concluded there was no goodwill impairment.

During the second quarter 2023, the Company determined that a triggering event had occurred for the Engineered Materials reporting unit indicating it was more likely than not that the fair value of this goodwill was less than the associated carrying value. This determination resulted from the persistence of the challenging operating conditions, customer destocking and underlying demand weakness that contributed to a revised outlook reflecting a further reduction in near-term forecasted operating results, growth projections, as well as an additional decrease in market capitalization. Therefore, the Company performed a goodwill impairment assessment as of June 1, 2023 and recorded a goodwill impairment charge of $349.0 million, reflected within “Impairment and other charges” on the consolidated statement of operations.

As of October 1, 2024, the Company combined the management of its Engineered Materials, Plastics Solutions and Polystyrene businesses. Certain components of the Plastics Solutions segment were combined with the Polystyrene segment and renamed Polymer Solutions to better reflect the Company’s strategic focus on providing solutions in areas such as sustainability and material substitution. Impairment assessments on each reporting unit were performed immediately before and after the change in organizational structure where it was concluded there was no goodwill impairment for the year ended December 31, 2024.

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As of December 31, 2025, the remaining $67.7 million in total goodwill is allocated to the reportable segments as follows: $35.6 million to Polymer Solutions, $16.3 million to Latex Binders, and $15.8 million to Engineered Materials, with no amounts allocated to the Americas Styrenics segment.

Factors which could result in future impairment charges, among others, include changes in worldwide economic conditions, changes in technology, changes in competitive conditions and customer preferences, and fluctuations in foreign currency exchange rates. These factors are discussed in Item 7A—Quantitative and Qualitative Disclosures about MarketRisk and Item 1A— Risk Factors included in this Annual Report.

Income Taxes

We account for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences of temporary differences between the carrying amounts and tax bases of assets and liabilities using enacted rates. The effect of a change in tax rates on deferred taxes is recognized in income in the period that includes the enactment date.

Deferred taxes are provided on the outside basis differences and unremitted earnings of subsidiaries outside of Ireland. All undistributed earnings of foreign subsidiaries and affiliates are expected to be repatriated as of December 31, 2025. Based on the evaluation of available evidence, both positive and negative, we recognize future tax benefits, such as net operating loss carryforwards and tax credit carryforwards, to the extent that realizing these benefits is considered to be more likely than not.

As of December 31, 2025, we had net deferred tax liabilities of $28.4 million, after valuation allowances of $442.7 million. In evaluating the ability to realize the deferred tax assets, we rely on, in order of increasing subjectivity, taxable income in prior carryback years, the future reversals of existing taxable temporary differences, tax planning strategies and forecasted taxable income using historical and projected future operating results.

For the year ended December 31, 2025, Management assessed whether there were any changes in facts and circumstances that would result in any changes to the valuation allowance conclusions reached in the prior years. During the year ended December 31, 2025, Management believed there was enough negative evidence to determine that it was no longer more likely than not that the net deferred tax assets would be realized in some of the Company’s European subsidiaries, primarily France, Germany and the Netherlands. Among this evidence is the overall cumulative losses of its Europe operations, as well as Management’s recognition that these subsidiaries’ ability to generate taxable income in the future is no longer considered reliable or sustainable. These negative factors combined with no other tax planning strategies identified that could allow the Company to utilize its deferred tax asset, resulted in Management’s decision to establish a full valuation allowance against the net deferred tax asset position during the year ended December 31, 2025.

As of December 31, 2025, we had deferred tax assets for tax loss carryforward of approximately $256.7 million, $42.5 million of which is subject to expiration in the years between 2026 and 2030. We continue to evaluate our historical and projected operating results for several legal entities for which we maintain valuation allowances on net deferred tax assets.

We are subject to income taxes in Ireland, Luxembourg, the United States and numerous foreign jurisdictions, and are subject to income tax audits within these jurisdictions. The tax provision includes amounts considered sufficient to pay assessments that may result from examinations of prior year tax returns; however, the amount ultimately paid upon resolution of issues raised may differ from the amounts accrued. Since significant judgment is required to assess the future tax consequences of events that have been recognized in our financial statements or tax returns, the ultimate resolution of these events could result in adjustments to our financial statements and such adjustments could be material. Therefore, we consider such estimates to be critical in preparation of our financial statements.

The financial statement effect of an uncertain income tax position is recognized when it is more likely than not, based on the technical merits, that the position will be sustained upon examination. Accruals are recorded for other tax contingencies when it is probable that a liability to a taxing authority has been incurred and the amount of the contingency can be reasonably estimated. Uncertain income tax positions have been recorded in “Other noncurrent obligations” in the consolidated balance sheets for the periods presented.

Management judgment is required in determining our provision for income taxes, our deferred tax assets and liabilities, and any valuation allowance recorded against our deferred tax assets. The valuation allowance is based on our estimates of future taxable income and the period over which we expect the deferred tax assets to be recovered. Our

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estimate of future taxable income is based on management’s judgment and assumptions about various factors including historical experience and results, cyclicality of the business, and future industry and macroeconomic conditions and trends. Changes in these assumptions in future periods may require we adjust our valuation allowance, which could materially impact our financial position and results of operations.

Pension Plans and Postretirement Benefits

We have various company-sponsored retirement plans covering substantially all employees. We also provide certain health care and life insurance benefits to retired employees in the United States (the “OPEB Plans”). The OPEB plans provide health care benefits, including hospital, physicians’ services, drug and major medical expense coverage, and life insurance benefits. We recognize the underfunded or overfunded status of a defined benefit pension or postretirement plan as an asset or liability in our consolidated balance sheets and recognize changes in the funded status in the year in which the changes occur through AOCI, which is a component of shareholders’ equity.

A settlement is a transaction that is an irrevocable action that relieves the employer (or the plan) of primary responsibility for a pension or postretirement benefit obligation, and that eliminates significant risks related to the obligation and the assets used to effect the settlement. The Company does not record settlement gains or losses during interim periods when the cost of all settlements in a year is less than or equal to the sum of the service cost and interest cost components of net periodic benefit cost for the plan in that year.

Pension benefits associated with these plans are generally based on each participant’s years of service, compensation, and age at retirement or termination. The discount rate is an important element of expense and liability measurement. We evaluate our assumptions at least once each year, or as facts and circumstances dictate, and make changes as conditions warrant.

We determine the discount rate used to measure plan liabilities as of the December 31 measurement date for the pension and postretirement benefit plans. The discount rate reflects the current rate at which the associated liabilities could be effectively settled at the end of the year. We set our discount rates to reflect the yield of a portfolio of high quality, fixed-income debt instruments that would produce cash flows sufficient in timing and amount to settle projected future benefits.

We use a fully-yield curve approach in the estimation of the future service and interest cost components of net periodic benefit cost for our defined benefit pension and other postretirement benefit plans by applying the specific spot rates along the yield curve used in the determination of the benefit obligation to the relevant projected cash flows. Service cost related to our defined benefit pension plans and other postretirement plans is included within “Cost of sales” and “Selling, general and administrative expenses,” whereas all other components of net periodic benefit cost are included within “Other expense (income), net” in the consolidated statements of operations.

We determine the expected long-term rate of return on assets by performing an analysis of historical and expected returns based on the underlying assets, which generally are insurance contracts. We also consider our historical experience with pension fund asset performance. The expected return of each asset class is derived from a forecasted future return confirmed by current and historical experience. Future actual net periodic benefit cost will depend on the performance of the underlying assets and changes in future discount rates, among other factors.

The weighted average assumptions used to determine pension plan obligations and net periodic benefit costs are provided below:

​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

​ ​ Non-U.S. Plans ​ U.S. Plan ​ OPEB Plans ​

​ ​ December 31, ​ December 31, ​ December 31, ​

Pension and other postretirement plan obligations: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Net periodic benefit costs: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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Holding all other factors constant, a 0.25% increase (decrease) in the discount rate used to determine net periodic benefit cost would decrease (increase) 2026 pension expense for our non-U.S. plans by approximately $1.0 million and $(0.9) million, respectively. Holding all other factors constant, a 0.25% increase (decrease) in the long-term rate of return on assets used to determine net periodic benefit cost for our non-U.S. plans would decrease (increase) 2026 pension expense by approximately $0.1 million and $(0.1) million, respectively. Holding all other factors constant, a 0.25% increase or decrease in the discount rate, or the long-term rate of return on assets, used to determine net periodic benefit cost for our U.S. plan would change our 2026 pension expense by less than $0.1 million.

Plan assets totaled $108.2 million and $106.7 million as of December 31, 2025 and 2024. As noted above, plan assets are invested primarily in insurance contracts that provide for guaranteed returns. Investments in the pension plan insurance contracts are valued utilizing unobservable inputs, which are contractually determined based on returns, fees, and the present value of the future cash flows, or cash surrender values, of the contracts, and are classified as Level 3 investments. The Company presents certain pension plan assets valued at net asset value per share as a practical expedient outside of the fair value hierarchy.

Recent Accounting Pronouncements

We describe the impact of recent accounting pronouncements in Note 2 of the consolidated financial statements, included elsewhere within this Annual Report.

Item 7A. Quantitative and Qualitative Disclosures About Market Risk

We are exposed to changes in interest rates and foreign currency exchange rates because we finance certain operations through fixed and variable rate debt instruments and denominate our transactions in a variety of foreign currencies. We are also exposed to changes in the prices of certain commodities that we use in production. Changes in these rates and commodity prices may have an impact on future cash flows and earnings. We manage these risks through normal operating and financing activities and, when deemed appropriate, through the use of derivative financial instruments. We do not enter into financial instruments for trading or speculative purposes.

By using derivative instruments, we are subject to credit and market risk. The fair market value of the derivative instruments is determined by using valuation models whose inputs are derived using market observable inputs, including interest rate yield curves, as well as foreign exchange and commodity spot and forward rates, and reflects the asset or liability position as of the end of each reporting period. When the fair value of a derivative contract is positive, the counterparty owes us, thus creating a receivable risk for us. We are exposed to counterparty credit risk in the event of non-performance by counterparties to our derivative agreements. We minimize counterparty credit (or repayment) risk by entering into transactions with various major financial institutions of investment grade credit rating.

Our exposure to market risk is not hedged in a manner that completely eliminates the effects of changing market conditions on earnings or cash flows.

Interest Rate Risk

Given the Company’s debt structure, we have certain exposure to changes in interest rates. Refer to Note 16 in the consolidated financial statements for further information regarding the Company’s debt facilities.

The Company’s 2028 Refinance Term Loans bear interest at a rate per annum equal to Term SOFR (as defined in the 2028 Refinance Credit Agreement) plus 8.50%, subject to a 3.00% SOFR floor. The Company’s 2028 Term Loan B bears an interest rate of SOFR plus 2.50% (subject to a 0.00% SOFR floor). The Company’s 2024 Term Loan B bore an interest rate of LIBOR plus 2.00% (subject to a 0.00% LIBOR floor) as of December 31, 2022. Based on weighted average outstanding borrowings under the 2028 Term Loan B and 2028 Refinance Term Loans for the year ended December 31, 2025, an increase in 100 basis points in SOFR would have resulted in approximately $1.4 million of additional interest expense for the period.

Loans under the OpCo Super-Priority Revolver, at the Borrowers’ option, may be maintained as (a) SOFR loans, which bear interest at a rate per annum equal to SOFR plus the applicable margin (as defined in the Credit Agreement), if applicable, or (b) base rate loans which shall bear interest at a rate per annum equal to the base rate plus the applicable margin (as defined in the Credit Agreement). As of December 31, 2025, the Borrowers are required to pay a quarterly

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commitment fee in respect of any unused commitments under the OpCo Super-Priority Revolver equal to 0.375% per annum. As of December 31, 2025, the Company had $75.0 million of variable debt issued under our OpCo Super-Priority Revolver and during the year ended December 31, 2025 the Company drew $265.0 million and repaid $190.0 million from the facility. As such, we incurred $3.3 million variable rate interest related to the OpCo Super-Priority Revolver during the period.

Our 2024 Accounts Receivable Securitization Facility is subject to interest charges on both the amount of outstanding borrowings as well as the amount of available, but undrawn commitments under the facility. As of December 31, 2025, the Accounts Receivable Securitization Facility borrowings bear interest at a rate per annum equal to Adjusted Term SOFR or EURIBOR (each as defined in the Accounts Receivable Securitization Facility credit agreement, subject to a 1.00% floor), depending on the borrowing currency, plus a margin of 4.75% and the Company incurs interest on a minimum of $75.0 million of advances, irrespective of actual amounts outstanding. As of December 31, 2025, the Company had $118.0 million of variable debt issued under our Accounts Receivable Securitization Facility and during the year ended December 31, 2025 the Company drew $145.0 million and repaid $102.0 million from the facility. As such, we incurred $12.1 million variable rate interest related to our Accounts Receivable Securitization Facility during the period.

Foreign Currency Exchange Rate Risks

The Company’s ongoing business operations expose us to foreign currency risks, including fluctuating foreign exchange rates. Our primary foreign currency exposure is the euro-to-U.S. dollar exchange rate, noting that approximately 46% of our net sales were generated in Europe for the year ended December 31, 2025. To a lesser degree, we are also exposed to the exchange rates between the U.S. dollar and other currencies, including, among others, the Chinese yuan, South Korean won, Swiss franc, and New Taiwan dollar. To manage these risks, the Company periodically enters into derivative financial instruments such as foreign exchange forward contracts.

Certain subsidiaries have monetary assets and liabilities denominated in currencies other than their respective functional currencies, which creates foreign exchange risk. Our principal strategy in managing exposure to changes in foreign currency exchange rates is to naturally hedge the foreign currency-denominated liabilities on our consolidated balance sheets against corresponding assets of the same currency such that any changes in liabilities due to fluctuations in exchange rates are offset by changes in their corresponding foreign currency assets. In order to further reduce our exposure, we use foreign exchange forward contracts to economically hedge the impact of the variability in exchange rates on our monetary assets and liabilities denominated in certain foreign currencies. These derivative contracts are not designated for hedge accounting treatment.

The Company also enters into forward contracts with the objective of managing the currency risk associated with forecasted U.S. dollar-denominated raw materials purchases by one of our subsidiaries whose functional currency is the euro. By entering into these forward contracts, which are designated as cash flow hedges, the Company buys a designated amount of U.S. dollars and sells euros at the prevailing market rate to mitigate the risk associated with the fluctuations in the euro-to-U.S. dollar foreign currency exchange rate. The qualifying hedge contracts are marked-to-market at each reporting date and any unrealized gains or losses are included in AOCI to the extent effective, and reclassified to cost of sales in the period during which the transaction affects earnings or it becomes probable that the forecasted transaction will not occur. As of December 31, 2025, the Company does not have any outstanding forward contracts for the purposes of hedging its exposure to the euro. The Company continues to monitor prevailing rate forecasts and its euro-denominated exposure to determine when to enter into these forward contracts. A 1% change in the euro will impact our annual profitability by approximately $0.7 million on a pre-tax basis.

We have legal entities consolidated in our financial statements that have functional currencies other than the U.S. dollar, our reporting currency. As a result of currencies fluctuating against the U.S. dollar, currency translation gains and losses are recorded in other comprehensive income, primarily as a result of the remeasurement of our euro functional legal entities as of December 31, 2025, 2024, and 2023.

Raw Material Price Risk

We purchase certain raw materials such as styrene, butadiene, BPA, MMA, PC, and acetone primarily under short- and long-term supply contracts. The pricing terms for these raw material purchases are generally determined based on commodity indices and prevailing market conditions within the relevant geography. The selling prices of our products

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are generally based, in part, on the current or forecasted costs of our key raw materials but are often subject to a predetermined lag period for the pass through of these costs. As such, during periods of significant raw material price volatility, the Company may experience material volatility in earnings and cash flows due to the lag in passing through raw material costs, primarily for styrene, butadiene, MMA, and acetone. Assuming no changes in sales price, volume or mix, a hypothetical 10% change in the market price of our raw materials would have impacted cost of sales by approximately $193.7 million for the year ended December 31, 2025.

We mitigate the risk of volatility in raw material prices where possible by passing changes in raw material costs through to our customers by adjusting our prices or including provisions in our contracts that allow us to adjust prices in such a circumstance or by including pricing formulas which utilize commodity indices. Nevertheless, we may be subject to the timing differences described above for the pass through of these costs. In addition, even when raw material costs may be passed on to our customers, during periods of high raw material price volatility, customers without minimum purchase requirements with us may choose to delay purchases of our materials or, in some cases, substitute purchases of our materials with less costly products. We do not currently enter into derivative financial instruments to manage our price risk relating to our raw material contracts.

Commodity Price Risk

We purchase certain commodities, primarily natural gas, to operate facilities and generate heat and steam for various manufacturing processes, which purchases are subject to price volatility, generally based on commodity indices and prevailing market conditions within the relevant geography. In certain instances, the selling prices of our products are based, in part, on the current or forecasted costs of our key commodities but are subject to a predetermined lag period for the pass through of these costs. As such, during periods of significant commodity price volatility, the Company may experience material volatility in earnings and cash flows due to the lag in or inability to pass through these commodity costs.

We mitigate the risk of price fluctuations associated with these commodity purchases where possible by passing changes in commodity costs through to our customers by adjusting our prices or including provisions in our contracts that allow us to adjust prices in such a circumstance or by including pricing formulas which utilize commodity indices. Additionally, as deemed appropriate, we may enter into derivative financial instruments such as commodity swaps, which effectively converts a portion of our natural gas costs into a fixed rate obligation. Certain of these commodity swap agreements are designated as cash flow hedges, and as such, the contracts are marked-to-market at each reporting date and any unrealized gains or losses are included in AOCI to the extent effective, and reclassified to cost of sales in the period during which the transaction affects earnings or it becomes probable that the forecasted transaction will not occur. We may also enter into commodity swap agreements to economically hedge the impact of these price fluctuations, which are not designated for hedge accounting treatment. Inclusive of these hedges, a hypothetical 10% increase in natural gas prices will impact cost of sales by approximately $2.6 million.

Item 8. Financial Statements and Supplementary Data

The financial statements and supplementary data required by Regulation S-X are included in Item 15- Exhibits, Financial Statements Schedules contained in Part IV of this Annual Report.

Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure

None.

Item 9A. Controls and Procedures

Evaluation of Disclosure Controls and Procedures

Our management is responsible for establishing and maintaining disclosure controls and procedures designed to provide reasonable assurance that information required to be disclosed by us in our reports that we file or submit under the Exchange Act (as defined in Rules 13a-15e and 15d-15(e) of the Securities Exchange Act of 1934, as amended) is recorded, processed, summarized, and reported within the time periods specified in the SEC’s rules and forms, and that such information is accumulated and communicated to our management, including our Chief Executive Officer and

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Chief Financial Officer, as appropriate, to allow timely decisions regarding required disclosures. Our management, with the participation of our Chief Executive Officer and Chief Financial Officer, evaluated the effectiveness of the Company’s disclosure controls and procedures as of December 31, 2025. Based on that evaluation, the Chief Executive Officer and Chief Financial Officer concluded that our disclosure controls and procedures as of the end of the period covered by this Annual Report were effective to provide the reasonable level of assurance described above.

Management’s Annual Report on Internal Control over Financial Reporting

Management is responsible for establishing and maintaining adequate internal control over financial reporting, as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act. Internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of the Company’s financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with policies and procedures may deteriorate.

Management conducted an assessment of the Company’s internal control over financial reporting as of December 31, 2025, based on the framework in Internal Control—Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on the assessment, management concluded that, as of December 31, 2025, the Company’s internal control over financial reporting is effective.

The effectiveness of the Company’s internal control over financial reporting as of December 31, 2025 has been audited by PricewaterhouseCoopers LLP, an independent registered public accounting firm, as stated in their report which appears herein.

Changes in Internal Control over Financial Reporting

There was no change in our internal control over financial reporting (as defined in Rules 13a-15(f) and 15d-15(f) of the Exchange Act) that occurred during the year ended December 31, 2025 that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

The Company believes we have maintained appropriate internal controls during our initial phased implementation period and will continue to evaluate, test and monitor our internal controls over financial reporting for effectiveness as processes and procedures in each of these impacted areas evolve.

Item 9B. Other Information

Trading Arrangements

During the twelve months ended December 31, 2025, one director and one executive officer adopted trading arrangements intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Securities Exchange Act of 1934.

​ ​ ​ ​

Name Action Date Duration (1) Total Number of Shares to be Sold

(1) Unless earlier terminated pursuant to the terms of the trading arrangement.

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No other directors or executive officers of the Company adopted or terminated a trading arrangement intended to satisfy the affirmative defenses of Rule 10b5-1 under the Securities Exchange Act of 1934 or a “non-Rule 10b5-1 trading arrangement,” as defined in Item 408(a) of Regulation S-K, during the twelve months ended December 31, 2025.

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections

Not applicable.

Part III

Item 10. Directors, Executive Officers and Corporate Governance

Except as set forth below, the information required by this Item 10 is incorporated herein by reference from the sections captioned “Election of Directors,” “Corporate Governance,” “Board Structure and Committee Composition,” “Our Company’s Executive Officers,” and “Delinquent Section 16(a) Reports” of the Company’s definitive proxy statement for the 2026 annual general meeting of shareholders to be filed with the SEC pursuant to Regulation 14A under the Securities Exchange Act of 1934 (the “2026 Proxy Statement”) or will be included in an amendment to this Form 10-K (the “10-K/A”).

Code of Ethics

The Company has adopted a Code of Business Conduct applicable to all of our directors, officers and employees, and a Code of Ethics for Senior Financial Employees applicable to our principal executive, financial and accounting officers, and all persons performing similar functions. A copy of each of those Codes is available on the Company’s corporate website at www.trinseo.com under Investor Relations—Corporate Governance—Ethics and Compliance. If we make any substantive amendments to these Codes, or grant any waivers, including any implicit waivers from the provisions of these Codes, we will make a disclosure on our website or in a report on Form 8-K. Our Code of Business of Conduct is supported by a number of support policies which are specifically referenced in the Code, and most of which are also available on our corporate website. Our website and the information contained on that site, or accessible through that site, are not a part of, and are not incorporated by reference into, this Annual Report.

Insider Trading Policy

The Company has adopted an insider trading policy that governs the purchase, sale and/or other dispositions of our securities by our directors, officers and employees, as well as their immediate family members and others who may have access to material nonpublic information concerning the Company, and that is designed to promote compliance with insider trading laws, rules and regulations. The policy prohibits the unauthorized disclosure of any nonpublic information acquired in the workplace, the misuse of material nonpublic information in securities trading. All persons subject to the policy are prohibited from the purchase or sale of our securities except in designated trading windows or pursuant to preapproved 10b5-1 trading plans. Certain persons, including our executive officers and directors, must obtain preclearance prior to any trading in our securities. The policy also prohibits short sales, transactions in publicly traded options such as puts, calls or other derivatives, hedging transactions and other inherently speculative transactions.

Item 11. Executive Compensation

The information required by this Item 11 will be contained in our 2026 Proxy Statement or 10-K/A and is incorporated by reference herein.

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Shareholder Matters

The information required by this Item 12 will be contained in our 2026 Proxy Statement or 10-K/A and is incorporated by reference herein.

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Item 13. Certain Relationships and Related Transactions, and Director Independence

The information required by this Item 13 will be contained in our 2026 Proxy Statement or 10-K/A and is incorporated by reference herein.

Item 14. Principal Accounting Fees and Services

The information required by this Item 14 will be contained in our 2026 Proxy Statement or 10-K/A and is incorporated by reference herein.

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Part IV

Item 15. Exhibits, Financial Statement Schedules

(a) The following documents are filed as part of this report:

1. Financial statements:

​

Reports of Independent Registered Public Accounting Firms F-2

Consolidated Balance Sheets as of December 31, 2025 and 2024 F-6

​ ​

​

​

2. Exhibits: The exhibits to this report are listed in the exhibit index below.

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EXHIBIT INDEX

​

​

Exhibit No. ​ Description

​ ​ ​

​ ​ ​

​ ​ ​

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​ ​ ​

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​

Exhibit No. ​ Description

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Exhibit No. ​ Description

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​ ​ ​

​ ​ ​

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​

Exhibit No. ​ Description

​ ​ ​

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​

Exhibit No. ​ Description

​ ​ ​

​ ​ ​

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21.1 † ​ Subsidiaries of Trinseo PLC

​ ​ ​

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​ ​ ​

​ ​ ​

​ ​ ​

​ ​ ​

​ ​ ​

​ ​ ​

101.INS † ​ iXBRL Instance Document

​ ​ ​

101.SCH † ​ iXBRL Taxonomy Extension Schema Document

​ ​ ​

101.CAL † ​ iXBRL Taxonomy Extension Calculation Linkbase Document

​ ​ ​

101.DEF † ​ iXBRL Taxonomy Extension Definition Linkbase Document

​ ​ ​

101.LAB † ​ iXBRL Extension Label Linkbase Document

​ ​ ​

101.PRE † ​ iXBRL Taxonomy Extension Presentation Linkbase Document

​ ​ ​

​

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* Compensatory plan or arrangement.

§§ Certain portions of this exhibit were redacted pursuant to Item 601(b)(10)(iv) of Regulation S-K. The omitted information is (i) not material and (ii) would likely cause us competitive harm if publicly disclosed. We agree to furnish supplementally an unredacted copy of the exhibit to the Securities and Exchange Commission on its request; provided, however that the Company may request confidential treatment of this exhibit pursuant to Rule 24b-2 of the Securities Exchange Act of 1934, as amended.

† Filed herewith.

Item 16. Form 10-K Summary

None.

​

​

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SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: March 13, 2026

TRINSEO PLC

​ ​ ​

​ By: /s/ Frank Bozich

​ Name: Frank Bozich

​ Title: President and Chief Executive Officer(Principal Executive Officer)

​

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Pursuant to the requirements of the Securities Act of 1934, this report has been signed by the following persons in the capacities and on the dates indicated.

Signature Title ​ ​ ​ Date

​ ​

Frank Bozich ​ (Principal Executive Officer) ​

​ ​ ​ ​ ​

David Stasse ​ (Principal Financial Officer) ​

​ ​ ​ ​ ​

Roger E. Greene ​ (Principal Accounting Officer) ​

​ ​

/s/ Joseph Alvarado ​ Director ​ March 13, 2026

Joseph Alvarado ​ ​ ​ ​

​ ​ ​ ​ ​

/s/ Victoria Brifo ​ Director ​ March 13, 2026

Victoria Brifo ​ ​ ​ ​

​ ​ ​ ​ ​

/s/ Jeffrey J. Cote ​ Director ​ March 13, 2026

Jeffrey J. Cote ​ ​ ​ ​

​ ​ ​ ​ ​

/s/ Jeanmarie Desmond ​ Director ​ March 13, 2026

Jeanmarie Desmond ​ ​ ​ ​

​ ​ ​ ​ ​

/s/ Matthew T. Farrell ​ Director ​ March 13, 2026

Matthew T. Farrell ​ ​ ​ ​

​ ​ ​ ​ ​

/s/ Carol Flaton ​ Director ​ March 13, 2026

Carol Flaton ​ ​ ​ ​

​ ​ ​ ​ ​

/s/ Jill Frizzley ​ Director ​ March 13, 2026

Jill Frizzley ​ ​ ​ ​

​ ​ ​ ​ ​

/s/ K’Lynne Johnson ​ Chair and Director ​ March 13, 2026

K’Lynne Johnson ​ ​

​ ​

/s/ Sandra Beach Lin ​ Director ​ March 13, 2026

Sandra Beach Lin ​ ​

​ ​ ​ ​ ​

/s/ Henri Steinmetz ​ Director ​ March 13, 2026

Henri Steinmetz ​ ​ ​ ​

​

​

​

​

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INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

​

Audited Consolidated Financial Statements

Report of Independent Registered Public Accounting Firm (PCAOB ID 238) F-2

Report of Independent Registered Public Accounting Firm (PCAOB ID 34) F-5

Consolidated Balance Sheets as of December 31, 2025 and 2024 F-6

​

​

​

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Report of Independent Registered Public Accounting Firm

​

To theBoard of Directors and Shareholders of Trinseo PLC

​

Opinions on the Financial Statements and Internal Control over Financial Reporting

​

We have audited the accompanying consolidated balance sheets of Trinseo PLC and its subsidiaries (the “Company”) as of December 31, 2025 and 2024, and the related consolidated statements of operations, of comprehensive income (loss), of shareholders’ equity (deficit) and of cash flows for each of the three years in the period ended December 31, 2025, including the related notes and financial statement schedule listed in the accompanying index (collectively referred to as the “consolidated financial statements”). We also have audited the Company’s internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control – Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

​

In our opinion, based on our audits and the report of Deloitte & Touche LLP, the consolidated financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2025 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2025, based on criteria established in Internal Control - Integrated Framework (2013) issued by the COSO.

​

We did not audit the financial statements of Americas Styrenics LLC, a 50% equity investment of Trinseo PLC, which is reflected in the consolidated financial statements of Trinseo PLC as an equity method investment of $206.9 million and $222.6 million as of December 31, 2025 and 2024, respectively, and equity in earnings (losses) of unconsolidated affiliates of ($3.1) million, $15.4 million, and $62.1 million for each of the three years in the period ended December 31, 2025. Those statements were audited by Deloitte & Touche LLP whose report thereon has been furnished to us, and our opinion expressed herein, insofar as it relates to the amounts included for Americas Styrenics LLC, is based solely on the report of Deloitte & Touche LLP.

​

Substantial Doubt about the Company’s Ability to Continue as a Going Concern

​

The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern. As discussed in Note 2 to the consolidated financial statements, the Company has an accumulated deficit and negative cash flows from operations that raise substantial doubt about its ability to continue as a going concern. Management's plans in regard to these matters are described in Note 1. The consolidated financial statements do not include any adjustments that might result from the outcome of this uncertainty.

​

Basis for Opinions

​

The Company's management is responsible for these consolidated financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting, included in Management's Annual Report on Internal Control over Financial Reporting appearing under Item 9A. Our responsibility is to express opinions on the Company’s consolidated financial statements and on the Company's internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

​

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud, and whether effective internal control over financial reporting was maintained in all material respects.

​

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Our audits of the consolidated financial statements included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits and the report of Deloitte & Touche LLP provide a reasonable basis for our opinions.

​

Definition and Limitations of Internal Control over Financial Reporting

​

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

​

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

​

Critical Audit Matters

​

The critical audit matter communicated below is a matter arising from the current period audit of the consolidated financial statements that was communicated or required to be communicated to the audit committee and that (i) relates to accounts or disclosures that are material to the consolidated financial statements and (ii) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Accounting for Income Taxes

As described in Notes 2 and 8 to the consolidated financial statements, the Company recorded a provision for income taxes of $42.6 million for the year ended December 31, 2025, and has deferred tax assets of $50.7 million (including a valuation allowance of $442.7 million), deferred tax liabilities of $79.1 million, and liabilities for uncertain tax positions of $10.9 million as of December 31, 2025. The Company is, or has been, subject to income taxes in Ireland, the United States and numerous other foreign jurisdictions, and is subject to income tax audits within these jurisdictions. Management measures deferred taxes as the difference between the financial and tax basis of the Company’s assets and liabilities which are adjusted for changes in tax rates and tax laws when changes are enacted. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not that a tax benefit will not be realized. As disclosed by management, the valuation allowance is based on management’s estimates of future taxable income and the period over which they expect the deferred tax assets to be recovered. Management recognizes the financial statement effects of uncertain income tax positions when it is more likely than not, based on the technical merits, that the position will be sustained upon examination. Since significant judgment is required to assess the future tax consequences of events that have been recognized in the financial statements or tax returns, the ultimate resolution of these events could result in adjustments to the financial statements and such adjustments could be material.

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Table of Contents

​

The principal considerations for our determination that performing procedures relating to accounting for income taxes is a critical audit matter are (i) the significant judgment by management when determining the provision for income taxes, net deferred tax assets, including a valuation allowance, and liabilities for uncertain tax positions; and (ii) a high degree of auditor judgment and effort in performing procedures and evaluating audit evidence relating to these account balances and tax positions.

​

Addressing the matter involved performing procedures and evaluating audit evidence in connection with forming our overall opinion on the consolidated financial statements. These procedures included testing the effectiveness of controls relating to income taxes, including management’s controls over the establishment of deferred tax assets and liabilities, the assessment of the realizability of deferred tax assets, and the identification and recognition of the liability for uncertain tax positions. These procedures also included, among others (i) testing the provision for income taxes, including the effective tax rate reconciliation, and permanent and temporary differences; (ii) testing the completeness and accuracy of underlying data used in measuring and recognizing deferred tax assets and liabilities; (iii) evaluating management’s assessment of the realizability of deferred tax assets on a jurisdictional basis; (iv) evaluating the completeness of management’s assessment of the identification of uncertain tax positions; and (v) evaluating the status and results of income tax audits with the relevant tax authorities.

​

/s/ PricewaterhouseCoopers LLP

Philadelphia, Pennsylvania

March 13, 2026

​

We have served as the Company’s auditor since 2010.

​

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​

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

​

To the Members and the Board of Directors of

Americas Styrenics LLC

The Woodlands, Texas

​

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Americas Styrenics LLC and its subsidiaries (the "Company") as of December 31, 2025 and 2024, the related consolidated statements of comprehensive (loss) income, members' equity, and cash flows, for each of the three years in the period ended December 31, 2025, and the related notes (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and 2024, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2025, in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements are the responsibility of the Company's management. Our responsibility is to express an opinion on the Company's financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB and in accordance with auditing standards generally accepted in the United States of America. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company's internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matters

Critical audit matters are matters arising from the current-period audit of the financial statements that were communicated or required to be communicated to the audit committee and that (1) relate to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. We determined that there are no critical audit matters.

/s/ DELOITTE & TOUCHE LLP

Houston, Texas

February 25, 2026

We have served as the Company’s auditor since 2008.

F-5