31 U.S.C. § 3529

(a) A disbursing or certifying official or the head of an agency may request a decision from the Comptroller General on a question involving— (1) a payment the disbursing official or head of the agency will make; or (2) a voucher presented to a certifying official for certification. (b) (1) Except as provided in paragraph (2), the Comptroller General shall issue a decision requested under this section. (2) A decision requested under this section concerning a function transferred to or vested in the Director of the Office of Management and Budget under section 211(a) of the Legislative Branch Appropriations Act, 1996 ( 109 Stat. 535 ), as in effect immediately before the effective date of title II of the General Accounting Office Act of 1996, or under this Act, shall be issued— (A) by the Director of the Office of Management and Budget, except as provided in subparagraph (B); or (B) in the case of a function delegated by the Director to another agency, by the head of the agency to which the function was delegated.