If an internal auditor suspects fraud during an engagement, the expected action is to evaluate the suspected activities to determine whether a formal investigation is warranted. This step is crucial as it ensures that suspicions are substantiated before escalating the issue, thereby maintaining the integrity and objectivity of the internal audit process. This approach aligns with the IIA’s guidance on handling fraud, including assessing and responding to risks of fraud during audit engagements.

The Institute of Internal Auditors (IIA) - International Standards for the Professional Practice of Internal Auditing