Trinseo (NYSE: TSE) SVP Cooney reports tax-withholding share dispositions

Rhea-AI Filing Summary

Trinseo PLC senior vice president and chief human resources officer Paula M. Cooney reported two tax-related share dispositions tied to vesting restricted stock units. On February 21, 2026, 7,440 ordinary shares were withheld at $0.3276 per share to satisfy tax obligations. On February 22, 2026, a further 2,684 shares were similarly withheld at $0.3276 per share. After these transactions, Cooney directly owned 125,988 ordinary shares.

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^*

Cooney Paula M.

(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, CHRO

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		7,440(1)	D	$0.3276	128,672	D
Ordinary Shares	02/22/2026		F		2,684(1)	D	$0.3276	125,988	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	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).
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FAQ

What did Trinseo (TSE) executive Paula M. Cooney report in this Form 4?

Paula M. Cooney reported two tax-withholding dispositions of Trinseo ordinary shares. These transactions covered taxes due on vesting restricted stock units rather than open-market sales, and were executed at a reported price of $0.3276 per share.

How many Trinseo (TSE) shares were disposed of for tax withholding?

A total of 10,124 Trinseo ordinary shares were disposed of for tax withholding. This included 7,440 shares on February 21, 2026 and 2,684 shares on February 22, 2026, all tied to restricted stock unit vesting.

What transaction code and price were reported in the Trinseo (TSE) Form 4?

Both transactions used code F, indicating shares withheld to pay taxes or exercise price. The reported price per Trinseo ordinary share was $0.3276 for each disposition, reflecting the value applied in calculating the tax-withholding share amounts.

Are these Trinseo (TSE) transactions open-market sales by the executive?

No, these transactions are not open-market sales. The Form 4 identifies them as tax-withholding dispositions, meaning Trinseo withheld shares from vested restricted stock units to satisfy tax obligations, rather than the executive selling shares on the market.

How many Trinseo (TSE) shares does Paula M. Cooney own after the transactions?

After the reported tax-withholding dispositions, Paula M. Cooney directly owns 125,988 Trinseo ordinary shares. This post-transaction holding reflects the remaining equity stake following the withholding of shares to cover associated tax liabilities.