BlackRock, Inc. filed an amended beneficial ownership statement with the SEC on October 27, 2026, disclosing its holdings in Trinseo PLC common stock as of the September 30, 2026 reporting event date.

Key Highlights

  • Aggregate beneficial ownership: BlackRock, Inc. reported 105,889 shares of Trinseo PLC common stock beneficially owned in total.
  • Percent of class: The 105,889 shares represent 0.3% of Trinseo PLC's outstanding common stock, according to the filing.
  • Sole voting power: BlackRock reported sole voting power over 77,219 shares, with zero shares subject to shared voting power.
  • Sole dispositive power: BlackRock reported sole dispositive power over all 105,889 shares, with no shared dispositive power.
  • Event date: The filing identifies September 30, 2026 as the date of the event requiring this statement.
  • Filer classification: BlackRock, Inc. is identified as a parent holding company (type "HC"), organized in Delaware, filing on behalf of certain reporting business units.

BlackRock's Amended Ownership Position in Trinseo PLC

According to the filing, BlackRock, Inc., headquartered at 50 Hudson Yards, New York, NY 10001, submitted Amendment No. 1 to its beneficial ownership statement covering common stock of Trinseo PLC, a specialty materials and plastics company whose principal executive offices are located at 440 East Swedesford Road, Suite 301, Wayne, PA 19087. The CUSIP number for the covered securities is G9059U107.

The filing states that this statement "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." The document notes that the filing does not include securities, if any, beneficially owned by other business units whose beneficial ownership has been disaggregated in accordance with SEC Release No. 34-39538 dated January 12, 1998. The filing was signed by Spencer Fleming, Managing Director, on October 27, 2026.

Regarding dividends and proceeds from sales, the filing discloses that "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," but specifies that no single person's interest exceeds five percent of the total outstanding common shares. The filing also certifies that the securities "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."

What Was Disclosed

BlackRock, Inc. disclosed aggregate beneficial ownership of 105,889 shares of Trinseo PLC common stock, equal to 0.3% of the class, as of September 30, 2026, with sole voting power over 77,219 shares and sole dispositive power over all 105,889 shares.