Chief Accounting Officer — Tommy E. Darby: The filing announces the external hire of a new Chief Accounting Officer, with the predecessor transitioning to a different internal role rather than leaving the company.

Results of Operations and Financial Condition. On August 4, 2026 , Westlake Corporation (the "Company"), issued a press release announcing its 2026 second quarter results. A copy of the press release is furnished with this Current Report as Exhibit 99.1. The information furnished pursuant to this Current Report, including Exhibit 99.1, shall not be deemed to be "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and will not be incorporated by reference…

Other Events. As previously reported in Westlake Corporation’s (the “Company” or “Westlake”) periodic filings under the Securities Exchange Act of 1934, as amended, the Company and other ethylene consumers have been named as defendants in a series of fourteen civil lawsuits (collectively, the “Ethylene Antitrust Litigation”) in the Netherlands and Germany. On July 29, 2026, the District Court of Amsterdam dismissed the plaintiffs’ claims against the Company and the other defendants in (i) the…

Regulation FD Disclosure On June 15, 2026, Westlake Corporation (the “Company”) issued a press release announcing that Westlake Vinnolit GmbH & Co. KG, a wholly owned subsidiary of the Company, has completed the previously announced acquisition of a polyvinyl chloride and vinyl chloride monomer production site located in Wilhelmshaven, Germany. A copy of the press release is furnished with this Current Report on Form 8-K as Exhibit 99.1. The information furnished pursuant to this Current Repo…

Results of Operations and Financial Condition. On May 5, 2026 , Westlake Corporation (the "Company"), issued a press release announcing its 2026 first quarter results. A copy of the press release is furnished with this Current Report as Exhibit 99.1. The information furnished pursuant to this Current Report, including Exhibit 99.1, shall not be deemed to be "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and will not be incorporated by reference into…

Chief Financial Officer — Jonathan H. Baksht: Jonathan H. Baksht was appointed as the new Chief Financial Officer, succeeding Mr. M. Steven Bender who is retiring.

Other Events. As previously reported in Westlake Corporation’s (the “Company” or “Westlake”) periodic filings under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), the Company and other manufacturers of polyvinyl chloride (PVC) pipe and fittings have been named as defendants in ten putative class action civil lawsuits filed in Illinois between August 2024 and June 2025 (the “PVC Pipe Antitrust Litigation”), which generally allege that PVC pipe and fittings manufacturers…

Entry into a Material Definitive Agreement. On April 2, 2026, Westlake Corporation (“ Westlake ”) entered into a credit agreement (the “ Credit Agreement ”), by and among Westlake, the lenders from time to time party thereto (collectively, the “ Lenders ”), the issuing banks party thereto and JPMorgan Chase Bank, National Association, as administrative agent. Under the Credit Agreement, the Lenders have committed to provide an unsecured revolving credit facility in an aggregate principal amou…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information set forth in

Termination of a Material Definitive Agreement. The information set forth in

Executive Vice President, Performance & Essential Materials Segment Head — Robert F. Buesinger: Mr. Buesinger is transitioning to a Special Advisor role due to retirement, with Brian Powers appointed as the new Segment Head.

Results of Operations and Financial Condition. On February 24, 2026 , Westlake Corporation (the "Company") issued a press release announcing its 2025 fourth quarter and full year results. A copy of the press release is furnished with this Current Report as Exhibit 99.1. The information furnished pursuant to this Current Report, including Exhibit 99.1, shall not be deemed to be "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and will not be incorporat…

Chief Financial Officer — M. Steven Bender: The CFO is retiring, but the departure is orderly with a successor to be appointed.

Regulation FD Disclosure On January 5, 2026, Westlake Corporation (the "Company" or "Westlake") issued a press release announcing that it completed its previously announced acquisition of the global compounding solutions businesses of the ACI/Perplastic Group. A copy of the press release is furnished with this Current Report as Exhibit 99.1. The information furnished pursuant to this Current Report, including Exhibit 99.1, shall not be deemed to be "filed" for the purposes of Section 18 of th…

Costs Associated with Exit or Disposal Activities. On December 12, 2025, Westlake Corporation (the “Company”) approved a plan to cease operation of certain of the Company’s North American chlorovinyl production facilities, including (i) its polyvinyl chloride (“PVC”) plant at the Aberdeen, Mississippi site, which has an annual capacity of approximately 1 billion pounds of suspension PVC, (ii) its vinyl chloride monomer (“VCM”) plant at the Lake Charles, Louisiana North site, which has an annu…

Regulation FD Disclosure. On November 10, 2025, Westlake Corporation (“Westlake”) issued a press release (the “Pricing Press Release”) attached hereto as Exhibit 99.1, announcing the pricing of its previously announced cash tender offer (the “Tender Offer”) for any and all of its outstanding 3.600% Senior Notes due 2026. On November 10, 2025, Westlake issued a press release (the “Results Press Release”) attached hereto as Exhibit 99.2, announcing the expiration and results of the Tender Offer…

Entry into a Material Definitive Agreement. On November 4, 2025, Westlake Corporation (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with BofA Securities, Inc., Deutsche Bank Securities Inc., J.P. Morgan Securities LLC and Wells Fargo Securities, LLC, for themselves and as representatives of the other underwriters named therein (the “Underwriters”), with respect to the issuance and sale in an underwritten public offering (the “Offering”) by the Company o…

Regulation FD Disclosure Tender Offer On November 4, 2025, Westlake Corporation (the “Company”) issued a press release announcing the commencement of a cash tender offer (the “Tender Offer”) for any and all of its outstanding 3.600% Senior Notes due 2026. The Tender Offer is subject to the terms and conditions set forth in the Offer to Purchase, dated November 4, 2025. A copy of the press release is attached as Exhibit 99.1 to this report and is incorporated by reference herein. Senior Notes…

Results of Operations and Financial Condition. On October 30, 2025 , Westlake Corporation (the "Company"), issued a press release announcing its 2025 third quarter results. A copy of the press release is furnished with this Current Report as Exhibit 99.1. The information furnished pursuant to this Current Report, including Exhibit 99.1, shall not be deemed to be "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and will not be incorporated by reference…

Results of Operations and Financial Condition. On August 5, 2025 , Westlake Corporation (the "Company"), issued a press release announcing its 2025 second quarter results. A copy of the press release is furnished with this Current Report as Exhibit 99.1. The information furnished pursuant to this Current Report, including Exhibit 99.1, shall not be deemed to be "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and will not be incorporated by reference…

Costs Associated with Exit or Disposal Activities As previously disclosed, in July 2024, Westlake Corporation (the "Company") approved a plan to mothball the allyl chloride ("AC") and epichlorohydrin ("ECH") units at the Company's site in Pernis, the Netherlands. The Company has continued to operate the liquid epoxy resin ("LER") and bisphenol A ("BPA") units at the Pernis facility. In light of the continued deterioration of the Company's business in Europe, on June 13, 2025, the Company init…

Results of Operations and Financial Condition. On May 2, 2025 , Westlake Corporation (the "Company"), issued a press release announcing its 2025 first quarter results. A copy of the press release is furnished with this Current Report as Exhibit 99.1. The information furnished pursuant to this Current Report, including Exhibit 99.1, shall not be deemed to be "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and will not be incorporated by reference into…

Executive Vice President — Robert F. Buesinger: The filing discloses a special compensation award (RSUs) to a sitting executive, not a departure, appointment, or board election.

CEO — Jean-Marc Gilson: The filing discloses a compensatory arrangement (special RSU award) for the CEO, not a change in management status or departure.

Results of Operations and Financial Condition. On February 24, 2025 , Westlake Corporation (the "Company") issued a press release announcing its 2024 fourth quarter and full year results. A copy of the press release is furnished with this Current Report as Exhibit 99.1. The information furnished pursuant to this Current Report, including Exhibit 99.1, shall not be deemed to be "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and will not be incorporat…