According to IIA guidance, the internal audit charter is a critical document that defines the purpose, authority, and responsibility of the internal audit activity. It is endorsed by the organization ' s governing body and establishes the internal audit function ' s position within the organization, including its reporting lines and access to records and personnel.

To assess whether the independence of the internal audit activity is at risk of being compromised, reviewing the internal audit charter provides the best source of evidence. This document outlines the independence and objectivity of the internal audit function and specifies the reporting structure to senior management and the board, which are essential elements in safeguarding independence.

IIA Standard 1000: Purpose, Authority, and Responsibility

IIA Practice Guide: Independence and Objectivity