Independent inspections of audit firms are a fundamental regulatory instrument of preventative oversight regarding auditors of public interest entities (PIEs). While the definition of PIEs varies from jurisdiction to jurisdiction, at a minimum, it includes listed companies. In some jurisdictions auditor oversight also extends to non-PIE auditors.

The purpose of inspections is to probe into and improve audit quality. This is usually done by reviewing particular areas of the internal quality control system of an audit firm as well as looking into the performance of selected audit engagements.

Inspections of audit firms are an external quality assurance procedure within the framework of Article 29 of the Audit Directive 2006/43/EG and the European Commission's Recommendation on external quality assurance for statutory auditors and audit firms auditing public interest entities (notified under document number C(2008) 1721).