Audit working papers are documents prepared or obtained by auditors that provide evidence of the audit work performed. They include information used to plan and conduct the audit, as well as evidence to support the auditor's opinion. Working papers serve several purposes, such as providing evidence of compliance with auditing standards, supporting the conclusions in the audit report, and allowing for review of the audit work. They must be organized, indexed, and signed or initialed by the preparer and reviewer. Working papers are the property of the auditing firm but may be subpoenaed by a court.