Trinseo: BlackRock reports 0.3% ownership stake

BlackRock reported sole voting power over 77,219 shares and sole dispositive power over 105,889 shares.

Rhea-AI Filing Summary

Trinseo PLC’s amended Schedule 13G reports BlackRock, Inc. beneficial ownership of 105,889 common shares, equal to 0.3% of the class. BlackRock reported sole voting power over 77,219 shares and sole dispositive power over 105,889 shares; shared voting and dispositive power were both zero.

The reported position reflects securities attributed to certain BlackRock business units and subsidiaries and affiliates, excluding other business units whose holdings are disaggregated. BlackRock also stated that various persons may receive dividends or sale proceeds, but no one person’s interest exceeds 5% of Trinseo’s outstanding common shares.

Key Figures

Beneficial ownership: 105,889 shares Percent of class: 0.3% Sole voting power: 77,219 shares +3 more

6 metrics

Beneficial ownership 105,889 shares BlackRock, Inc.

Percent of class 0.3% BlackRock, Inc.

Sole voting power 77,219 shares BlackRock, Inc.

Sole dispositive power 105,889 shares BlackRock, Inc.

Shared voting power 0 shares BlackRock, Inc.

Shared dispositive power 0 shares BlackRock, Inc.

Key Terms

beneficially owned, sole voting power, sole dispositive power, Reporting Business Units

4 terms

beneficially owned financial

"securities beneficially owned"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole voting power financial

"Sole voting power to vote or to direct the vote"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

sole dispositive power financial

"Sole power to dispose or to direct the disposition"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Reporting Business Units financial

"collectively, the "Reporting Business Units""

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many TSEOQ shares did BlackRock report beneficially owning?

BlackRock, Inc. reported beneficial ownership of 105,889 Trinseo common shares, or 0.3% of the class. The reported position reflects certain BlackRock business units and affiliated entities, excluding other business units whose holdings are disaggregated.

How many TSEOQ shares did BlackRock have voting and dispositive power over?

BlackRock reported sole voting power over 77,219 shares and sole dispositive power over 105,889 shares. Shared voting and dispositive power were both zero.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/27/2026 - 05:27 PM EDT Accepted by SEC EDGAR 10/27/2026 - 05:25 PM EDT Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

TRINSEO PLC

(Name of Issuer)

Common Stock

(Title of Class of Securities)

G9059U107

(CUSIP Number)

09/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): G9059U107

1

Names of Reporting Persons

BlackRock, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 77,219.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 105,889.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

105,889.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

0.3 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: TRINSEO PLC
(b)	Address of issuer's principal executive offices: 440 EAST SWEDESFORD ROAD, SUITE 301 WAYNE PA 19087
Item 2.
(a)	Name of person filing: BlackRock, Inc. In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by certain business units (collectively, the "Reporting Business Units") of BlackRock, Inc. and its subsidiaries and affiliates. It does not include securities, if any, beneficially owned by other business units whose beneficial ownership of securities are disaggregated from that of the Reporting Business Units in accordance with such release.
(b)	Address or principal business office or, if none, residence: BlackRock, Inc., 50 Hudson Yards New York, NY 10001
(c)	Citizenship: See Item 4 of Cover Page
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: G9059U107
Item 4.	Ownership
(a)	Amount beneficially owned: 105889
(b)	Percent of class: 0.3 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 77219
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 105889
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Various persons have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of the common stock of TRINSEO PLC. No one person's interest in the common stock of TRINSEO PLC is more than five percent of the total outstanding common shares.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See Exhibit 99
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

BlackRock, Inc.

Signature:	Spencer Fleming
Name/Title:	Managing Director
Date:	10/27/2026

Exhibit Information

Exhibit 24: Power of Attorney Exhibit 99: Item 7