According to IIA guidance, when assembling an engagement team to audit a vendor, it is crucial to include internal auditors who have expertise in investigating vendor fraud. This expertise is essential for identifying and assessing fraud risks associated with the vendor and ensuring a thorough and effective audit. While proficiency in financial statement analysis and local accounting principles is valuable, the specific context of vendor fraud requires specialized knowledge in that area.
IIA Standards: 1210.A2 - Proficiency
IIA Practice Guide: Auditing Third-Party Risk Management

The chief audit executive should review the latest guidance from the Institute of Internal Auditors (IIA) to ensure the internal audit charter complies with current standards. This approach ensures the charter reflects up- to-date practices and mandatory elements, maintaining the integrity and effectiveness of the internal audit function.
References:
"International Standards for the Professional Practice of Internal Auditing," which provides mandatory guidance on the internal audit charter.

Administering control questionnaires to individuals with primary responsibilities in the process can yield valuable information about processes and controls. However, one significant drawback is that the information gathered may be limited regarding the actual functionality of the controls. This approach relies on the respondents' knowledge and perceptions, which may not accurately reflect the effectiveness of the controls in practice. Moreover, respondents might not fully understand the auditor's intentions or may provide biased or incomplete information, thereby limiting the depth of insights into how controls function in real-world scenarios.
IIA Standard 2201: Planning Considerations
IIA Practice Guide: Assessing the Adequacy of Risk Management Processes

In internal auditing, reviewing the vendor master file for authorizations is a test to ensure that only authorized vendors are in the system, which directly relates to the effectiveness of control measures in place. This means verifying that the controls are effective in preventing unauthorized or fraudulent vendors from being added, thereby safeguarding the organization against potential risks such as fraud, unauthorized transactions, or compliance violations.
Institute of Internal Auditors (IIA), International Standards for the Professional Practice of Internal Auditing (Standards), Standard 2120 - Risk Management.

To identify a personal conflict-of-interest situation affecting an organization's procurement function, inspecting documents is the most effective engagement technique. This involves reviewing relevant documentation such as procurement records, conflict of interest disclosures, vendor contracts, and employee relationships with vendors. This technique provides concrete evidence and can reveal discrepancies or relationships that suggest a conflict of interest, offering a clear and objective basis for any findings.
The Institute of Internal Auditors (IIA) - Standards for the Professional Practice of Internal Auditing, Standard
2310 - Identifying Information