26 U.S.C. § 6406 — Prohibition of administrative review of decisions

In the absence of fraud or mistake in mathematical calculation, the findings of fact in and the decision of the Secretary^* upon the merits of any claim presented under or authorized by the internal revenue laws and the allowance or non-allowance by the Secretary of interest on any credit or refund under the internal revenue laws shall not, except as provided in subchapters C and D of chapter 76 (relating to the Tax Court^*), be subject to review by any other administrative or accounting officer, employee^*, or agent of the United States.