[Form 4] Trinseo PLC Insider Trading Activity

Rhea-AI Filing Summary

Form 4 filing summary: On 06/21/2025 Trinseo PLC (TSE) director Mark E. Tomkins reported a transaction coded F, indicating the withholding of 10,105 ordinary shares at $3.73 each to satisfy taxes due upon the vesting of previously granted restricted stock units. Because the shares were withheld by the company rather than sold in the open market, the action is considered non-discretionary and does not signal a change in investment sentiment.

Following the transaction, Tomkins retains direct ownership of 36,619 shares. No derivative securities were acquired or disposed of, and there were no additional transactions disclosed. The document was signed on 06/24/2025 by an attorney-in-fact on Tomkins’ behalf.

Overall, the filing represents a routine tax-related adjustment with minimal financial impact on either the insider’s stake or the company’s share structure.

Insights

Securities Analyst

TL;DR: Routine tax withholding; no market signal, negligible impact on insider ownership or float.

This Form 4 shows an internal share withholding to cover payroll taxes triggered by RSU vesting. The transaction code F confirms it was automatic and not an elective sale, so it carries little informational value for investors. The dollar amount is modest (~$38k) relative to Trinseo’s market capitalization, and the director still holds a meaningful 36,619-share position, maintaining alignment with shareholders. I classify the disclosure as neutral and not impactful for valuation or sentiment.

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^*

TOMKINS MARK E

(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		10,105(1)	D	$3.73	36,619	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

Why did Trinseo (TSE) insider Mark E. Tomkins dispose of 10,105 shares?

The shares were automatically withheld to pay taxes owed on the vesting of restricted stock units; no open-market sale occurred.

What was the transaction price reported in the Form 4 for TSE?

The withholding was recorded at $3.73 per share.

How many Trinseo shares does Mark E. Tomkins own after the transaction?

He directly holds 36,619 ordinary shares following the withholding.

Does this Form 4 indicate insider selling pressure at Trinseo?

No. Code F signifies tax withholding, not a discretionary sale, and thus offers little insight into selling intent.

When was the Form 4 for Trinseo filed and signed?

The form covers a transaction on 06/21/2025 and was signed on 06/24/2025.