[Form 4] Trinseo PLC Insider Trading Activity

Rhea-AI Filing Summary

Trinseo PLC (TSE) – Form 4 insider filing

Director Pierre-Marie De Leener reported a single transaction dated 06/21/2025 coded “F”, indicating shares were withheld by the company to satisfy tax obligations upon the vesting of previously granted restricted stock units. A total of 20,001 ordinary shares were disposed of at an implied price of $3.73 per share (≈ $74.6 thousand in value). Following the tax-related withholding, the director’s direct beneficial ownership stands at 36,174 shares.

The filing does not reflect an open-market sale or purchase initiated by the insider; therefore, it carries limited informational weight regarding insider sentiment. No derivative securities were involved, and there is no indication of a 10b5-1 trading plan.

Positive

• Director retains 36,174 shares after the transaction, maintaining equity alignment with shareholders.

Negative

• 20,001 shares disposed (withheld for taxes), slightly reducing insider ownership.

Insights

Corporate Governance Analyst

TL;DR: Tax-withholding disposition; director still holds 36k shares—neutral signal, minimal market impact.

The “F” code confirms this was an involuntary share disposition tied to RSU vesting taxes, not an elective sale. While 20,001 shares were surrendered, the director retains a meaningful equity stake, suggesting continued alignment with shareholder interests. The modest dollar value (under $0.1 million) and absence of additional transactions make the event non-material for valuation models or governance assessments. Accordingly, I view the disclosure as routine housekeeping with neutral market implications.

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^*

De Leener Pierre-Marie

(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)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
06/21/2025

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	06/21/2025		F		20,001(1)	D	$3.73	36,174	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 previously granted restricted stock units.

	/s/ Angelo Chaclas, Attorney-in-Fact	06/24/2025
	** 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

How many Trinseo (TSE) shares did Director Pierre-Marie De Leener dispose of?

The filing shows 20,001 ordinary shares were withheld to cover taxes.

What was the reason for the share disposal reported in Trinseo's Form 4?

The shares were withheld by the company to pay taxes on vested restricted stock units (transaction code “F”).

What is the director's remaining shareholding in Trinseo after the transaction?

After the withholding, the director owns 36,174 shares directly.

Was a 10b5-1 trading plan involved in this Form 4 filing for TSE?

No; the filing does not indicate that the transaction was made under a 10b5-1 plan.

Does this Form 4 suggest a change in insider sentiment toward Trinseo stock?

Likely not, as the transaction was tax-related rather than a discretionary sale or purchase.