The document provides guidance for supervisors on assessing the effectiveness of internal audit functions at banks. It outlines 20 principles related to supervisory expectations, the relationship between supervisors and internal audit, and the supervisory assessment of internal audit. The principles emphasize that internal audit should be independent, competent, and provide assurance to the board and management on risk management and controls. Supervisors should regularly communicate with internal audit and assess whether it has sufficient standing, authority and operates according to sound principles.