Investor Bulletin: An Introduction to PCAOB Inspections

November 18, 2025

This document represents the views of the Public Company Accounting Oversight Board (PCAOB) Office of the Investor Advocate and not necessarily those of other PCAOB staff or the Board. It is not a rule, policy, or statement of the Board.

One of the most important ways that the PCAOB protects investors is through inspections of audit firms. In other words, PCAOB inspects the auditors.

This bulletin introduces PCAOB inspections and provides links to key PCAOB resources that provide in-depth information about the inspection process.

Which Audit Firms Does the PCAOB Inspect?

Over 1,600 public accounting firms around the globe are registered with the PCAOB. PCAOB inspects the registered auditors for U.S.-listed public companies and broker-dealers registered with the Securities and Exchange Commission (SEC). These firms range from member firms in the “Big Four” multinational networks to smaller accounting firms.

In 2024, PCAOB staff inspected over 230 audit firms, reviewing over 900 audit engagements. Seventy-eight firms inspected were outside of the U.S., including firms in mainland China and Hong Kong, and we reviewed their work on more than 200 issuer audits.

• GO DEEPER: Visit the PCAOB’s Basics of Inspections page.

What Do PCAOB Inspectors Look for?

PCAOB inspections assess compliance with the Sarbanes-Oxley Act, the rules of the Board, SEC rules, and professional standards.

PCAOB inspections are designed to review portions of selected audits and to evaluate the sufficiency of a firm’s system of quality control.

While individual inspections vary, PCAOB inspectors’ reviews of audits tend to focus on areas they believe to be of greater complexity, areas of greater significance or with a heightened risk of material misstatement to the issuer’s financial statements, and areas of recurring deficiencies. For each selected audit area, the inspection team reviews the engagement team’s work papers and interviews engagement personnel regarding those audit areas.

The inspection evaluation of a firm’s system of quality control includes reviewing the design and operation of the firm’s policies and procedures in areas such as the firm’s tone at the top, independence policies and procedures, and engagement acceptance and retention.

If a potential deficiency is identified, inspectors engage with the firm and may review additional documentation. 

• GO DEEPER: Visit the PCAOB Inspection Procedures page.
  

Inspection Reports

The results of PCAOB inspections are included in publicly available inspection reports on the PCAOB’s website. The public reports include deficiencies in the specific audits reviewed by inspectors. However, by law, criticisms of a firm’s system of quality control are only made public if those criticisms are not satisfactorily addressed within 12 months of the report’s issuance.

• GO DEEPER: Visit the PCAOB’s Firm Inspection Reports page.
  

Other Resources

• Watch the PCAOB’s video, “Auditing the Auditors.”
• Read more about the relevance of audits in the Investor Bulletin, “Why Audits Matter.”
• Stay up to date on other Investor Bulletins and Advisories on the PCAOB’s resources page.