Tax withholding reduces Trinseo (TSE) SVP Angelo Chaclas’ share count

Rhea-AI Filing Summary

Trinseo PLC senior vice president and chief legal officer Angelo N. Chaclas reported two share dispositions that were automatic tax withholdings rather than open-market sales. On February 21, 2026, 3,690 Ordinary Shares were withheld at $0.3276 per share, and on February 22, 2026, a further 7,098 Ordinary Shares were withheld at the same price. According to the disclosure, these shares were withheld by the company to pay taxes due upon the vesting of restricted stock units, and Chaclas held 282,405 Ordinary Shares directly following the February 22 transaction.

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

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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^*

Chaclas Angelo N.

(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, CLO, CCO & CORP. SEC.

3. Date of Earliest Transaction (Month/Day/Year)
02/21/2026

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	02/21/2026		F		3,690(1)	D	$0.3276	289,503	D
Ordinary Shares	02/22/2026		F		7,098(1)	D	$0.3276	282,405	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	02/24/2026
	** 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 Trinseo (TSE) disclose in this Form 4 for Angelo N. Chaclas?

The Form 4 shows Angelo N. Chaclas had Trinseo shares withheld for taxes, not sold in the market. The company retained the shares to satisfy tax obligations when his restricted stock units vested.

How many Trinseo (TSE) shares were withheld for Angelo N. Chaclas’ taxes?

A total of 10,788 Trinseo Ordinary Shares were withheld to cover taxes. This included 3,690 shares on February 21, 2026 and 7,098 shares on February 22, 2026, both at a price of $0.3276 per share.

Was Angelo N. Chaclas selling Trinseo (TSE) shares on the open market?

No, the transactions were coded as tax-withholding dispositions, not open-market sales. The shares were withheld by Trinseo to pay taxes due at the time his restricted stock units vested, per the filing footnote.

What is the transaction code “F” in the Trinseo (TSE) Form 4?

The Form 4 uses transaction code “F” to indicate payment of tax liability by delivering securities. In this case, Trinseo withheld Ordinary Shares from Angelo N. Chaclas to cover taxes triggered by restricted stock unit vesting.

How many Trinseo (TSE) shares does Angelo N. Chaclas hold after these transactions?

Following the February 22, 2026 tax-withholding disposition, Angelo N. Chaclas directly held 282,405 Trinseo Ordinary Shares. This number reflects his ownership after the company withheld shares to satisfy his related tax obligations.

Why were Trinseo (TSE) shares withheld from Angelo N. Chaclas?

The shares were withheld by Trinseo to pay taxes due when his restricted stock units vested. Instead of paying cash for taxes, a portion of his vested shares was retained by the company to satisfy the tax liability.