Reperformance is a CAATs approach that involves independently executing the same procedures as the original process to verify the accuracy of the application's calculations. This approach maximizes the use of CAATs because it directly tests the functionality and reliability of the system by ensuring that the system processes transactions and calculations correctly, as intended by management.
IIA References:
* IIA Standard 1220: Due Professional Care suggests that internal auditors should apply appropriate techniques, such as CAATs, to obtain sufficient evidence. Reperformance as a CAATs method is particularly effective in verifying the integrity of system calculations.
* The Practice Guide on Using CAATs highlights that reperformance is one of the most powerful techniques for validating that a system operates as intended and that transactions are processed correctly.

According to IIA guidance on due professional care, internal auditors should perform thorough and adequate steps to verify the accuracy and legitimacy of transactions. When reviewing cash disbursements, it is essential to check the three-way match among the invoice, purchase order, and receiving report. This ensures that the payment is valid, authorized, and that the goods or services were actually received as ordered. This step is crucial in preventing and detecting errors and fraud, thereby ensuring that the audit findings are reliable and accurate.
:
IIA Standard 1220: Due Professional Care
IIA Practice Guide: Auditing Accounts Payable and Disbursements

When an internal auditor identifies a potential control deficiency based on a preliminary survey, such as the lack of established procedures for adding and approving new vendors, the next appropriate step is to gather more detailed information. Interviewing personnel involved in the accounts payable function allows the auditor to understand the context, confirm the accuracy of the questionnaire responses, and gain insights into the potential risks and impacts associated with the observed deficiency. This step is crucial before documenting the issue or planning further audit procedures to ensure the information is accurate and complete.
The IIA's International Standards for the Professional Practice of Internal Auditing, Standard 2201 - Planning Considerations.

Direct observation by the auditor provides the strongest and most reliable evidence of inventory existence, per IIA Standard 2310: Identifying Information. Observational evidence is primary and directly verifiable, whereas third-party confirmations (Option B) or photographs (Option D) may be manipulated. Interviews with personnel (Option C) provide insight but lack objectivity and reliability compared to physical observation. This aligns with the CIA syllabus emphasis on collecting sufficient and appropriate audit evidence (Part 2: Section II).

The primary reason for interviewing operational management during engagement planning is to understand the objectives of the area or process under review. This ensures that the audit aligns with business goals and assesses the relevance of internal controls.
* Validating the engagement work program (A) occurs later in the planning process.
* Assessing management's knowledge of risks and controls (C) is important but not the primary purpose of interviews.
* Reviewing past action plans (D) is relevant for follow-up audits, not initial engagement planning.
Reference:IIA's Practice Guide: Engagement Planning - Understanding the Business Process and Risks.