31 USC 713 - Audit of Internal Revenue Service, Tax and Trade Bureau, and Bureau of Alcohol, Tobacco, Firearms, and Explosives

(a) Under regulations of the Comptroller General, the Comptroller General shall audit the Internal Revenue Service and the Tax and Trade Bureau, Department of the Treasury, and the Bureau of Alcohol, Tobacco, Firearms, and Explosives, Department of Justice of the Department of the Treasury.[1] An audit under this section does not affect a final decision of the Secretary of the Treasury under section 6406 of the Internal Revenue Code of 1986 (26 U.S.C. 6406).
(b) 
(1) To carry out this section and to the extent provided by and only subject to section 6103 of the Internal Revenue Code of 1986 (26 U.S.C. 6103)
(A) returns and return information (as defined in section 6103(b) of the Internal Revenue Code of 1986 (26 U.S.C. 6103 (b)) shall be made available to the Comptroller General; and
(B) records and property of, or used by, the Service or either Bureau, shall be made available to the Comptroller General.
(2) At least once every 6 months, the Comptroller General shall designate each officer and employee of the Government Accountability Office by name and title to whom returns, return information, or records or property of the Service or either Bureau that can identify a particular taxpayer may be made available. Each designation or a certified copy of the designation shall be sent to the Committee on Finance of the Senate, the Committee on Ways and Means of the House of Representatives, the Committee on Governmental Affairs of the Senate, the Committee on Government Operations of the House, the Joint Committee on Taxation, the Commissioner of Internal Revenue, the Tax and Trade Bureau, Department of the Treasury, and the Director of the Bureau of Alcohol, Tobacco, Firearms, and Explosives, Department of Justice.
(3) Except as expressly provided by law, an officer or employee of the Office may make known information derived from a record or property of, or in use by, the Service or either Bureau that can identify a particular taxpayer only to another officer or employee of the Office whose duties or powers require that the record or property be made known.
[1] So in original.