Key audit tests are vital procedures auditors use to gather sufficient and appropriate audit evidence. These tests are categorized into risk assessment, tests of controls, and substantive procedures. Audit sampling is a practical tool used throughout these phases, enabling auditors to evaluate a subset of data and draw conclusions about the entire population. This improves audit efficiency while maintaining reliability and coverage.

Consider a practical example: an internal audit of a company’s employee reimbursement process. During the risk assessment phase, the auditor identifies potential risks such as duplicate claims or expenses submitted without receipts. To explore this, the auditor samples 20 reimbursement claims from different departments. The sample reveals that several claims are missing proper documentation, indicating a potential weakness in the approval process.

Next, during the test of controls, the auditor evaluates whether the control—mandatory manager approval before reimbursement—is functioning as intended. A sample of 30 high-value claims (e.g., over $1,000) is selected, and 6 are found to be processed without the required approval. This suggests that the control is not consistently applied and may not be reliable.

Finally, the auditor performs substantive procedures to assess whether the recorded expense amounts are accurate and free from material misstatement. A sample of 25 claims is tested against supporting receipts and bank payment records. Any discrepancies, such as inflated amounts or incorrect vendor names, are noted and investigated further.

In this example, audit sampling allows the auditor to focus on higher-risk transactions without reviewing every claim. It supports effective planning, control evaluation, and error detection—ensuring key audit tests are thorough, targeted, and efficient.