Trinseo (NYSE: TSE) director forfeits 42,484 RSUs in Form 4

Rhea-AI Filing Summary

Trinseo PLC director Sandra Beach Lin reported an “other” transaction involving 42,484 Ordinary Shares tied to restricted stock units. A footnote explains this reflects a voluntary forfeiture of RSUs granted on June 25, 2025 that had not yet vested or settled. After the adjustment, she directly holds 44,776 Ordinary Shares, so the filing reflects a compensation change rather than a market trade.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider LIN SANDRA BEACH

Role null

Type	Security	Shares	Price	Value
Other	Ordinary Shares	42,484	$0.00	--

Holdings After Transaction: Ordinary Shares — 44,776 shares (Direct, null)

Footnotes (1)

1. [object Object]

Key Figures

Restructured RSUs: 42,484 units Shares after transaction: 44,776 Ordinary Shares Transaction price: $0.00 per share

3 metrics

Restructured RSUs 42,484 units Voluntary forfeiture of previously granted RSUs

Shares after transaction 44,776 Ordinary Shares Direct holdings following Form 4 transaction

Transaction price $0.00 per share Code J “other” transaction with no cash consideration

Key Terms

restricted stock units ("RSUs"), voluntary forfeiture, Ordinary Shares, Other acquisition or disposition

4 terms

restricted stock units ("RSUs") financial

"Reflects a voluntary forfeiture by the Reporting Person of restricted stock units ("RSUs") that were previously granted"

Restricted stock units (RSUs) are a company promise to give an employee shares of stock (or cash equivalent) in the future, but only after certain conditions—usually staying with the company for a set time or hitting performance goals—are met. Investors watch RSUs because when they vest they increase the number of shares outstanding and can lead insiders to sell shares, affecting share price, company dilution and the true cost of employee pay.

voluntary forfeiture financial

"Reflects a voluntary forfeiture by the Reporting Person of restricted stock units"

Ordinary Shares financial

"security_title": "Ordinary Shares""

Ordinary shares are a type of ownership stake in a company, giving shareholders a right to participate in the company’s profits and decision-making through voting. They are similar to owning a piece of a business, and their value can rise or fall based on the company's performance. Investors buy ordinary shares to potentially earn dividends and benefit from the company's growth over time.

Other acquisition or disposition financial

"transaction_code_description": "Other acquisition or disposition""

Form 4 Insider Transactions: What Each Field Means →

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^*

LIN SANDRA BEACH

(Last) (First) (Middle)

C/O TRINSEO PLC

440 EAST SWEDESFORD ROAD, SUITE 301

(Street)

WAYNE PENNSYLVANIA 19087

(City) (State) (Zip)

UNITED STATES

(Country)

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)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/12/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	05/12/2026		J(1)		42,484	D	(1)	44,776	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. Reflects a voluntary forfeiture by the Reporting Person of restricted stock units ("RSUs") that were previously granted on June 25, 2025. At the time of forfeiture, the RSU award was not vested or settled, in full or in part.

	/s/ Angelo Chaclas, Attorney-in-Fact	05/14/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did Trinseo (TSE) report for Sandra Beach Lin?

Trinseo director Sandra Beach Lin reported an “other” transaction involving 42,484 Ordinary Shares. A footnote states this represents voluntary forfeiture of unvested restricted stock units rather than a market buy or sell of Trinseo shares.

How many Trinseo shares does Sandra Beach Lin hold after this Form 4?

Following the reported transaction, Sandra Beach Lin directly holds 44,776 Ordinary Shares of Trinseo PLC. This figure comes from the post-transaction ownership line and reflects her remaining direct equity stake in the company.

Was the Trinseo Form 4 transaction a purchase or sale of shares?

The Form 4 does not report a purchase or sale. It shows an “other” transaction coded J, explained as voluntary forfeiture of previously granted, unvested restricted stock units that were never settled into actual Trinseo Ordinary Shares.

What does the forfeiture of 42,484 Trinseo RSUs mean for investors?

The forfeiture of 42,484 unvested RSUs is a compensation-related adjustment, not a market trade. It reduces potential future share delivery under that award but does not involve cash proceeds or an open-market transaction in Trinseo stock.

Why were Trinseo RSUs from June 25, 2025 forfeited by the director?

The footnote states the director voluntarily forfeited restricted stock units granted on June 25, 2025. At forfeiture, the RSU award was not vested or settled, in full or in part, so no actual Ordinary Shares changed hands in the market.