To achieve conformance with the Standards, the chief audit executive must include the activity of reporting the results of the quality assurance and improvement program (QAIP) to senior management and the board.
This is essential for maintaining transparency and accountability in the internal audit activity's efforts to uphold and enhance the quality of its operations.
IIA Standard 1300: Quality Assurance and Improvement Program.

Engaging a fraud specialist is most likely required when interrogating a suspected fraudster. This specific activity demands specialized skills in interviewing and understanding behavioral cues that are outside the typical expertise of internal auditors. The use of fraud specialists ensures that interrogations are conducted effectively and that the information obtained is reliable, without compromising legal or ethical standards.
The Institute of Internal Auditors (IIA) - International Standards for the Professional Practice of Internal Auditing

To ensure that auditors develop the appropriate skills for conducting audits, the internal audit activity should encourage continuous professional development and may institute policies promoting certification attainment.
This approach directly supports the development of a proficient audit team equipped with the necessary skills and knowledge to conduct effective audits. Policies that encourage earning certifications such as Certified Internal Auditor (CIA), Certified Information Systems Auditor (CISA), etc., directly contribute to this objective by setting professional development as a priority within the audit function.
The IIA's Guidelines on Continuing Professional Development and Standards for the Professional Practice of Internal Auditing

Under the circumstances described, the type of fraud most likely to occur is skimming. Skimming involves stealing cash before it is recorded on the organization's books. Since receipts were issued only upon request and the inventory manager had control over collecting and depositing payments, there is an opportunity for undetected theft of cash payments.
Common types of fraud in cash handling environments, as outlined in fraud detection and prevention resources by the IIA.