The following is a summary discussion of the material Irish tax considerations applicable to dividend withholding taxes that may be applicable to you. This discussion does not cover all tax matters that may be of importance to any particular shareholder and may not be relevant to every investor. It is not intended to be, nor should it be construed to be, legal or tax advice. This discussion is based on laws and regulations as they stand on the date posted and is subject to any change in law or regulations or changes in interpretation or application thereof (and which may possibly have a retroactive effect). Shareholders are strongly urged to consult their own tax advisors about the tax consequences of Irish withholding taxes, the availability of exemptions or benefits under tax treaties, or other U.S. federal, state, local and foreign tax considerations relating to dividends issued by Trinseo, or the acquisition, ownership and disposition of our ordinary shares. Links are provided for informational purposes only.

Dividend Withholding Tax Information

Trinseo Plc has established tax residence in Ireland, and as such, dividends are considered Irish source income and Irish dividend withholding tax (“DWT") rules apply. Beginning with the dividend payable on January 20, 2022, payments will be subject to an Irish withholding tax (at the current rate of 25%) on the amount of each dividend unless the shareholder that is beneficially entitled to the dividend is a resident of the United States or a resident of a country listed as a “relevant territory”, and has ensured that the required information is on file with their broker, bank, qualifying intermediary or transfer agent (see below for more detail). With these rules, the vast majority of Trinseo’s shareholders and beneficial owners are entitled to an exemption from DWT. The full list of relevant territories can be found by clicking on this link: Relevant Territories

Shareholders and beneficial owners who are not residents of a relevant territory are generally subject to DWT. There are limited exceptions, however, and if you are not a resident of a relevant territory, you should consult your tax advisor.

 Beneficial U.S. Shareholder DWT Exemption Requirements:

U.S. shareholders that are beneficial owners of Trinseo Plc shares held in the Depository Trust Company (“DTC”) through a bank, broker or qualifying intermediary, must have a valid U.S. address on the records of their bank, broker or qualifying intermediary on the record date of the dividend to be exempt from DWT.

 Registered U.S. Shareholder DWT Exemption Requirements:

U.S. shareholders with shares registered directly with Trinseo’s transfer agent, Computershare Trust Company, Inc. (“Computershare”), that have a U.S. address on file and held shares of Trinseo S.A. immediately prior to the completion of the Irish Redomicile transaction on October 8, 2021 will be exempt from DWT for a period of one year beginning from October 8, 2021. Note that effective October 8, 2022, all U.S. registered holders will be required to file either (i) a valid Irish Non-Resident Form V2 with Computershare, or (ii) a U.S. Certification of Residence (Form 6166) to be exempt from DWT. In certain circumstances, the Irish Non-Resident Form V2 will need to be certified by the U.S. tax authorities and you should consult your tax advisor.

 U.S. registered shareholders that became shareholders of Trinseo Plc after the completion of the Irish Redomicile transaction on October 8, 2021 are required to file either (i) a valid Irish Non-Resident Form V2, or (ii) a Form 6166 with Computershare by the dividend record date to be exempt from DWT. In certain circumstances, the Irish Non-Resident Form V2 will need to be certified by the U.S. tax authorities and you should consult your tax advisor.

To obtain Form 6166 from the IRS, U.S. shareholders should file Form 8802, Application for United States Residency Certification, with the IRS at least 45 days before the Form 6166 is needed.

 Non-U.S. Shareholder DWT Exemption Requirements

If you are a shareholder who is resident in a relevant territory, other than the U.S., that has an address in a relevant territory on file and were a shareholder of Trinseo S.A. immediately prior to the completion of the Irish Redomicile transaction on October 8, 2021, you will be exempt from DWT for a period of one year beginning from October 8, 2021. Beginning October 8, 2022, you will need to file a valid Irish Non-Resident Form V2 with Computershare to be exempt from DWT. Please note that in certain circumstances the form must be certified by the tax authority of the country in which you are a resident.

Shareholders in relevant territories that became shareholders of Trinseo Plc after the completion of the Irish Redomicile transaction on October 8, 2021 are required to file a valid Irish Non-Resident Form V2 with Computershare by the dividend record date to be exempt from DWT. Please note that in certain circumstances the form must be certified by the tax authority of the country in which you are a resident.

For your convenience, attached below are Irish Dividend Withholding Tax Forms (Forms V2) and Application for United States Residency Certification (Form 8802):