The audit charter is a document that defines the purpose, scope, authority, and responsibility of an IT audit organization. The audit charter should specify roles and responsibilities within an IT audit organization, such as who is accountable for approving the audit plan, who is responsible for conducting the audits, who is authorized to access the audit evidence, and who is accountable for reporting the audit results. The organizational chart, the engagement letter, and the annual audit plan are also important documents for an IT audit organization, but they do not specify roles and responsibilities as clearly and comprehensively as the audit charter.