EXPLANATORY NOTE

This Registration Statement on Form S-8 is being filed by the registrant, Trinseo PLC (the “Company”), for the purpose of increasing the number of shares of common stock to be issued under the Trinseo PLC Amended & Restated 2014 Omnibus Incentive Plan (the “Plan”) by 1,400,000 shares, from 6,175,000 shares to 7,575,000 shares. In accordance with General Instruction E to Form S-8, the Company incorporates by reference the contents of the Registration Statement on Form S-8 (Registration No. 333- 266696) filed on August 9, 2022, Registration Statement on Form S-8 (Registration No. 333-240195) filed on July 30, 2020 and Post-Effective Amendment No. 1 to such Registration Statement filed on October 8, 2021, the Registration Statement on Form S 8 (Registration No. 333-232925) filed on July 31, 2019 and Post-Effective Amendment No. 1 to such Registration Statement filed on October 8, 2021, and the Registration Statement on Form S-8 (Registration No. 333-196973) filed on June 23, 2014 and Post-Effective Amendment No. 1 to such Registration Statement filed on October 8, 2021. The shareholders of the Company approved a proposal to amend the Plan for this purpose at the annual general meeting of shareholders on June 14, 2023.

Item 8. Exhibits.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Wayne, Commonwealth of Pennsylvania on the 4th day of August, 2023.

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POWER OF ATTORNEY

Each officer and director of Trinseo PLC whose signature appears below constitutes and appoints Frank A. Bozich and David Stasse, and each of them singly, his true and lawful attorneys-in-fact and agents, with full power of substitution and resubstitution in each of them singly, for him and in his name, place and stead, and in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Statement on Form S-8 of Trinseo PLC, and to file the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting to the attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in or about the premises, as full to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that the attorneys-in-fact and agents or any of each of them or their substitutes may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

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