[Form 4] Trinseo PLC Insider Trading Activity

Rhea-AI Filing Summary

Trinseo PLC EVP and CFO David Phillip Stasse reported routine tax-related share withholdings, not open-market trades. On February 22, 2026, the company withheld 9,671 Ordinary Shares at $0.3276 per share to cover taxes, leaving him with 265,154 shares. On February 21, 2026, a similar tax-withholding disposition of 5,028 shares at $0.3276 per share left him with 274,825 shares. A footnote clarifies these shares were withheld by the company to pay taxes following the vesting of previously granted restricted stock units.

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

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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^*

Stasse David Phillip

(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)
	EVP AND CFO

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		5,028(1)	D	$0.3276	274,825	D
Ordinary Shares	02/22/2026		F		9,671(1)	D	$0.3276	265,154	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	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 insider activity did Trinseo (TSE) report for EVP and CFO Stasse?

Trinseo reported that EVP and CFO David Phillip Stasse had Ordinary Shares withheld by the company to cover tax obligations from vested restricted stock units, rather than executing open-market trades. These transactions are coded as tax-withholding dispositions on his Form 4 filing.

How many Trinseo (TSE) shares were withheld for taxes in the latest Form 4?

The Form 4 shows two tax-withholding dispositions of Trinseo Ordinary Shares: 9,671 shares on February 22, 2026, and 5,028 shares on February 21, 2026. Both transactions were used to satisfy tax liabilities from vested restricted stock units.

Did Trinseos EVP and CFO sell shares in the open market?

No, the Form 4 indicates tax-withholding dispositions, not open-market sales. Shares were withheld by Trinseo to pay taxes due upon vesting of restricted stock units, as explained in a footnote, which is a common administrative mechanism for equity compensation.

What were David Phillip Stasses Trinseo share holdings after these transactions?

After the February 22, 2026 tax-withholding disposition, David Phillip Stasse directly held 265,154 Trinseo Ordinary Shares. Following the February 21, 2026 transaction, his holdings were 274,825 shares, reflecting only the administrative share reductions for tax payments.

What does transaction code F mean in the Trinseo (TSE) Form 4?

Transaction code F on the Trinseo Form 4 denotes payment of an exercise price or tax liability by delivering securities. Here, it reflects shares withheld by the company to cover taxes from vesting restricted stock units held by EVP and CFO David Phillip Stasse.

Is the Trinseo (TSE) Form 4 for David Phillip Stasse considered routine?

Yes, the Form 4 reflects routine equity compensation administration. The company withheld shares to satisfy tax liabilities tied to vested restricted stock units, with no indication of discretionary open-market buying or selling by EVP and CFO David Phillip Stasse.