In the world of auditing, the terms assurance and attestation are often used interchangeably but have distinct meanings. Assurance services are independent professional services that improve the quality or context of information for decision-makers. These services can cover a broad range of subjects, including financial and non-financial data. Attestation services, a subset of assurance, involve issuing a report on subject matter that is the responsibility of another party—such as management. In attestation, the auditor provides a conclusion or opinion based on the evaluation of evidence.

Audit sampling plays a vital role in both services by allowing auditors to form conclusions without reviewing every item in a data set. For example, in an attestation engagement to verify a company’s compliance with environmental regulations, the auditor may sample a selection of emission reports from various factory sites to assess whether standards were consistently met.

In an assurance engagement, such as verifying the effectiveness of internal controls over financial reporting, the auditor might sample transaction logs or system access records to evaluate risk and control processes. In both cases, audit sampling provides sufficient, appropriate evidence while keeping the process efficient and focused, ensuring that users of the report can rely on the findings with confidence.