[Form 4] Trinseo PLC Insider Trading Activity

Rhea-AI Filing Summary

Insider transaction summary: An officer of Trinseo PLC reported a share disposition on 10/03/2025 when 2,067 ordinary shares were withheld by the company to satisfy tax withholding obligations following the vesting of restricted stock units. The shares were reported at a withholding price of $2.33 per share. After the withholding, the reporting person beneficially owned 89,691 ordinary shares directly. The Form 4 was filed by a single reporting person and signed by an attorney-in-fact on 10/07/2025.

Positive

• Continued ownership: Reporting person still holds 89,691 shares after withholding
• Transaction is administrative: Shares were withheld to cover taxes from vested RSUs, not reported as an open-market sale

Negative

• Shares reduced: 2,067 shares were disposed via withholding, lowering direct holdings
• Price disclosure limited: Report lists a withholding price of $2.33, but no broader context on recent market activity is provided

Insights

Corporate Insider Filings Analyst

Small tax-withholding disposition after RSU vesting, ownership retained.

The report shows a disposition of 2,067 shares on 10/03/2025 labeled as withheld to cover taxes from vested restricted stock units. This is a common administrative action when equity awards vest and taxes are due, not an open-market sale.

The remaining direct beneficial ownership of 89,691 shares means the reporting officer continues to hold a material stake. Watch filings within the next quarter for additional vesting-related withholdings or any open-market transactions if monitoring insider selling patterns.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Hendriks Han

(Last) (First) (Middle)

C/O TRINSEO PLC

440 EAST SWEDESFORD ROAD, SUITE 301

(Street)

WAYNE PA 19087

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Trinseo PLC [ TSE ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	SVP, CHIEF TECHNOLOGY OFFICER

3. Date of Earliest Transaction (Month/Day/Year)
10/03/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Ordinary Shares	10/03/2025		F		2,067(1)	D	$2.33	89,691	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Shares withheld by the Company to pay taxes due following the vesting of restricted stock units.

	/s/ Angelo Chaclas, Attorney-in-Fact	10/07/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What did the Trinseo (TSE) Form 4 filed on 10/07/2025 report?

The filing reports that on 10/03/2025 2,067 ordinary shares were withheld to satisfy taxes after RSU vesting, at a withholding price of $2.33 per share.

How many Trinseo (TSE) shares does the reporting officer own after the transaction?

The reporting person beneficially owned 89,691 ordinary shares following the reported withholding.

Was the Form 4 transaction an open-market sale?

No. The disposition is described as shares withheld by the company to pay taxes due following RSU vesting, not an open-market sale.

Who signed the Form 4 for the reporting person?

The form was signed by an attorney-in-fact, /s/ Angelo Chaclas, with a signature date of 10/07/2025.

What role does the reporting person hold at Trinseo (TSE)?

The reporting person is an officer and director, listed as SVP, Chief Technology Officer.