Demonstrating due professional care involves thorough testing and evaluation of evidence. The internal auditor exhibited due professional care by selecting a sample of purchase orders above a specific threshold and obtaining documentation for each to verify compliance with the required bidding process. This methodical approach ensures that audit findings are based on sufficient, appropriate evidence and that conclusions about the effectiveness of controls are well-supported.
International Standards for the Professional Practice of Internal Auditing, particularly those related to due professional care and evidence evaluation.