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Exhibit 31.4

CERTIFICATION OF CHIEF FINANCIAL OFFICER

I, David Stasse, certify that:

1.

I have reviewed this Amendment No. 1 to the annual report on Form 10-K/A of Trinseo PLC;

2.

Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

Date: April 27, 2026

By:

/s/ David Stasse

Name:

David Stasse

Title:

Chief Financial Officer