According to IIA guidance, which of the following actions best demonstrates due professional care by...

When an internal auditor discovers fraud-related red flags during an audit engagement, the action that best demonstrates due professional care is to perform further testing to verify the existence of fraud. This approach ensures that any findings of fraud are based on thorough investigation and sufficient evidence, rather than premature conclusions. This procedure aligns with the IIA's guidance on due diligence and the thorough investigation of anomalies.

IIA International Standards for the Professional Practice of Internal Auditing.