The internal audit charter is a formal document that defines the purpose, authority, and responsibility of the internal audit activity. It establishes the internal audit activity's position within the organization, authorizes access to records, personnel, and physical properties relevant to the performance of engagements, and defines the scope of internal audit activities. Final approval of the internal audit charter by the board ensures that there is a clear understanding and agreement on how the internal audit activity should function, thus supporting objectivity in carrying out its duties.

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