Klaviyo Inc

INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Stockholders and the Board of Directors of Klaviyo, Inc.

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Klaviyo, Inc. and subsidiaries (the “Company”) as of December 31, 2024 and 2023, the related consolidated statements of operations and comprehensive loss, changes in redeemable common stock and stockholders’ equity (deficit), 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 19, 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.

Revenue — Refer to Note 2 to the financial statements

Critical Audit Matter Description

The Company’s revenue is comprised primarily of subscription fees made up of a large volume of low-dollar subscription transactions, sourced from various applications and supporting databases. The processing and recording of revenue is highly automated and is based on the contractual terms with customers. Because of the nature of the Company’s subscription fees, the Company uses automated systems to process and record its revenue transactions.

Given the Company’s systems to process and record revenue are highly automated, auditing revenue is complex and challenging due to the extent of audit effort required and involvement of professionals with expertise in information technology (“IT”) necessary to identify, test, and evaluate the Company’s systems, software applications, and automated controls.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the Company’s systems that process revenue transactions included the following procedures, among others:

•With the assistance of our IT specialists, we:

◦Identified the significant systems used to process revenue transactions and tested the effectiveness of general IT controls over each of these systems, including testing of user access controls, change management controls, and IT operations controls.

◦Performed testing of system interface controls and automated controls within the relevant revenue streams, as well as the controls designed to ensure the accuracy and completeness of revenue.

•We tested internal controls over the Company’s relevant revenue business processes, including those in place to reconcile the various systems to the Company’s general ledger.

•We created data visualizations to evaluate recorded revenue and evaluate trends in the transactional revenue data.

•For a sample of revenue transactions, we compared the recorded revenue to source documents and tested the accuracy of the recorded revenue.

•For the revenue billed through a payment processor, we tested the reconciliation of the recorded revenue to total cash received during the year.

/s/Deloitte & Touche LLP

Boston, Massachusetts

February 19, 2025

We have served as the Company’s auditor since 2020.