STEPAN CO

Report of Independent Regist ered Public Accounting Firm

To the stockholders and the Board of Directors of Stepan Company

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Stepan Company and subsidiaries (the “Company”) as of December 31, 2024 and 2023, the related consolidated statements of income, comprehensive income, stockholders’ equity, and cash flows, for each of the three years in the period ended December 31, 2024, and the related notes (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2024, in conformity with accounting principles generally accepted in the United States of America.

We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company’s internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control – Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission and our report dated February 27, 2025, expressed an unqualified opinion on the Company’s internal control over financial reporting.

Basis for Opinion

These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current-period audit of the financial statements that was communicated or required to be communicated to the audit committee and that (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Contingencies — Maywood — Refer to Note 1 and Note 16 to the Financial Statements

Critical Audit Matter Description

The Company’s Maywood property site may be exposed to liabilities for the remediation of environmental contamination. Environmental loss contingencies are evaluated based on the likelihood of the Company incurring a liability and whether a loss or range of losses is reasonably estimable. The likelihood and amount of a loss or range of losses are estimated based on currently available information and assumptions related to the nature and extent of contamination and the methods and resulting costs of remediation. Past estimates for environmental liabilities are subject to adjustment as new facts emerge during the investigatory and remediation processes. Given the subjectivity of estimating the likelihood of a loss, the range of potential loss, and the amount of liability to recognize associated with the Maywood site, performing audit procedures to evaluate whether the environmental loss contingencies were appropriately recorded and disclosed as of December 31, 2024, required especially challenging, subjective, and complex auditor judgment and an increased extent of effort.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the environmental loss contingencies at the Maywood site included the following, among others:

• We tested the effectiveness of internal controls related to the Company’s development of the estimated environmental loss contingencies, including the assumptions related to the nature and extent of contamination and the methods and resulting costs of remediation.

• We inquired of Company legal counsel and external legal counsel to understand developments in environmental matters.

• We evaluated written responses received from Company legal counsel and external legal counsel as it relates to the environmental loss contingencies.

• We inquired of the Company’s third-party environmental specialists to understand developments in environmental matters.

• We searched data on the U.S. Environmental Protection Agency website to identify any additional information relevant to the specific property sites.

• We evaluated whether the assumptions related to the nature and extent of contamination and the methods and resulting costs of remediation used by the Company to determine the estimated losses or ranges of losses were reasonable by comparing those assumptions to decisions rendered by state and Federal environmental regulatory agencies, information provided by feasibility studies and remedial action plans developed. In addition, we tested payments made on the remediation of environmental contamination.

• If the Company’s reasonable estimate of loss for a remediation site is a range, we evaluated whether the amount of the liability recognized by the Company within that range was reasonable based on the facts and circumstances specific to the remediation site.

• We evaluated the Company’s environmental contingencies disclosures for consistency with our knowledge of the Company’s environmental matters.

/s/ Deloitte & Touche LLP

DELOITTE & TOUCHE LLP

Chicago, Illinois

We have served as the Company’s auditor since 2002.