United States Government Accountability Office

The United States Government Accountability Office (GAO) is a federal agency within the legislative branch of the United States government that provides auditing, evaluative, and investigative services for the United States Congress in an independent and nonpartisan capacity. It is headquartered in Washington, D.C. at the US General Accounting Office Building in Judiciary Square, and has a headquarters office annex at the Longworth House Office Building on Capitol Hill.
The GAO is the supreme audit institution of the federal government of the United States. It identifies its core "mission values" as: accountability, integrity, and reliability.