Trinseo (TSE) Proxy filing summary

Executive summary

• The annual general meeting is scheduled for September 23, 2026, with shareholders able to attend in the US or via video link in Ireland.

• Shareholders will vote on the election of eleven directors, executive compensation, and the ratification of PwC as auditor.

• Proxy materials and the 2025 Annual Report are available online, with options for electronic or paper delivery.

• Shareholders of record as of July 30, 2026, are entitled to vote, with each share carrying one vote.

Voting matters and shareholder proposals

• Proposals include electing eleven directors, advisory approval of executive compensation, and ratification of PwC as auditor.

• All proposals require a majority of votes cast; abstentions and broker non-votes have no effect.

• Shareholder proposals for the 2027 meeting must be submitted by April 3, 2027, to be included in proxy materials.

Board of directors and corporate governance

• The board consists of eleven directors, with a mix of industry, financial, and governance expertise.

• All directors except the CEO are independent under NYSE standards.

• Four standing committees: Audit, Compensation and Talent Development, Nominating and Corporate Governance, and Environmental, Health, Safety, Sustainability & Public Policy.

• Annual board and committee self-evaluations are conducted.

• Shareholders can communicate directly with the board via the Corporate Secretary.