WESTLAKE CORP

Explanatory Note

References in this Annual Report on Form 10-K (this "report") to "we," "our," "us" or like terms refer to Westlake Corporation ("Westlake" or the "Company").

Cautionary Statements about Forward-Looking Statements

The Private Securities Litigation Reform Act of 1995 provides safe harbor provisions for forward-looking information. Certain of the statements contained in this Form 10-K are forward-looking statements. All statements, other than statements of historical facts, included in this Form 10-K that address activities, events or developments that we expect, project, believe or anticipate will or may occur in the future are forward-looking statements. Forward-looking statements can be identified by the use of words such as "believes," "intends," "may," "should," "could," "anticipates," "expected" or comparable terminology, or by discussions of strategies or trends. Although we believe that the expectations reflected in such forward-looking statements are reasonable, we cannot give any assurances that these expectations will prove to be correct. Forward-looking statements relate to matters such as:

•the ultimate timing, outcome and results of integrating the operations of any acquisitions and the ultimate outcome of our operating efficiencies applied to the products and services; the effects of any such acquisition, including the combined company's future financial condition, results of operations, strategies and plans; and expected synergies and other benefits from any such acquisition and our ability to realize such synergies and other benefits;

•recoverability of the carrying value of our long-lived assets, including tangible assets and intangible assets with finite lives, and the fair value of our reporting units with goodwill;

•future operating rates, margins, cash flows and demand for our products;

•industry market outlook, including the price of crude oil, natural gas, ethane, housing starts and repair and remodeling activity;

•macroeconomic outlook, including elevated interest rates, inflation and possible recession;

•widespread outbreak of an illness or any other communicable disease, or any other public health crisis;

•production capacities;

•the impact of ongoing conflicts in the Middle East and between Russia and Ukraine;

•currency devaluation;

•our ability to borrow under our credit agreement;

•our ability to meet our liquidity needs;

•our ability to meet debt obligations under our debt instruments;

•our intended quarterly dividends;

•future capacity additions and expansions in the industries in which we compete;

•timing, funding and results of capital projects;

•pension plan obligations, funding requirements and investment policies;

•compliance with present and future environmental regulations and costs associated with environmentally related penalties, capital expenditures, remedial actions and proceedings, including any new laws, regulations or treaties that may come into force to limit or control carbon dioxide and other greenhouse gas emissions or to address other issues of climate change;

•recovery of losses under our insurance policies;

•effects of pending legal proceedings and settlements;

•timing of and amount of capital expenditures;

•increased costs and other effects of tariffs, antidumping duties, or other trade remedies imposed by the U.S. government or other governments, and any effects on trading relationships among the United States and other countries; and

•results of the closures of certain of our facilities, including the units located in Pernis, Netherlands, certain of the North American chlorovinyls production assets located in Louisiana and Mississippi, and the styrene production plant located in Louisiana (such as the timing and amount of recognition of related costs and our expectations regarding our financial performance following such closures).

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We have based these statements on assumptions and analyses in light of our experience and perception of historical trends, current conditions, expected future developments and other factors we believe were appropriate in the circumstances when the statements were made. Forward-looking statements by their nature involve substantial risks and uncertainties that could significantly impact expected results, and actual future results could differ materially from those described in such statements. While it is not possible to identify all factors, we continue to face many risks and uncertainties. Among the factors that could cause actual future results to differ materially are the risks and uncertainties discussed under "Risk Factors" and those described from time to time in our other filings with the SEC including, but not limited to, the following:

•general economic and business conditions, including inflation, interest rates and possible recession;

•the cyclical nature of the chemical and building products industries;

•the availability, cost and volatility of raw materials and energy;

•uncertainties associated with the United States, European and worldwide economies, including those due to political tensions and conflict in the Middle East, Russia and Ukraine and elsewhere;

•uncertainties associated with pandemic infectious diseases;

•uncertainties associated with climate change;

•the potential impact on demand for ethylene, polyethylene and polyvinyl chloride due to initiatives such as recycling and customers seeking alternatives to polymers;

•current and potential governmental regulatory actions in the United States and other countries;

•industry production capacity and operating rates;

•the supply/demand balance for our products;

•competitive products and pricing pressures;

•instability in the credit and financial markets;

•access to capital markets;

•terrorist acts;

•operating interruptions (including leaks, explosions, fires, weather-related incidents, mechanical failure, unscheduled downtime, delays in turnaround activities, labor difficulties, transportation interruptions, spills and releases and other environmental risks);

•changes in laws or regulations, including trade policies and tariffs;

•disruptions in global trade, including as a result of tariffs, trade restrictions, retaliatory trade measures or the effect of such actions on trading relationships;

•the effects of government shutdowns;

•technological developments;

•information systems failures and cyberattacks;

•foreign currency exchange risks;

•our ability to implement our business strategies; and

•creditworthiness of our customers.

Many of such factors are beyond our ability to control or predict. Any of the factors, or a combination of these factors, could materially affect our future results of operations and the ultimate accuracy of the forward-looking statements. These forward-looking statements are not guarantees of our future performance, and our actual results and future developments may differ materially from those projected in the forward-looking statements. Management cautions against putting undue reliance on forward-looking statements or projecting any future results based on such statements or present or prior earnings levels. Every forward-looking statement speaks only as of the date of the particular statement, and we undertake no obligation to publicly update or revise any forward-looking statements.

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Industry and Market Data

Industry and market data used throughout this Form 10-K were obtained through internal company research, surveys and studies conducted by unrelated third parties and publicly available industry and general publications. We have not independently verified market and industry data from external sources. While we believe internal company estimates are reliable and market definitions are appropriate, neither such estimates nor these definitions have been verified by any independent sources.

Production Capacity

Unless we state otherwise, annual production capacity estimates used throughout this Form 10-K represent rated capacity of the facilities at December 31, 2025. We calculated rated capacity by estimating the number of days in a typical year that a production unit of a plant is expected to operate, after allowing for downtime for regular maintenance, and multiplying that number by an amount equal to the unit's optimal daily output based on the design feedstock mix. Because the rated capacity of a production unit is an estimated amount, actual production volumes may be more or less than the rated capacity.

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