26 U.S.C. § 7491 Burden of proof
(a) Burden shifts where taxpayer produces credible evidence(1) General ruleIf, in any court proceeding, a taxpayer introduces credible evidence with respect to any factual issue relevant to ascertaining the liability of the taxpayer for any tax imposed by subtitle A or B, the Secretary shall have the burden of proof with respect to such issue. (2) LimitationsParagraph (1) shall apply with respect to an issue only if—(A) the taxpayer has complied with the requirements under this title to substantiate any item; (B) the taxpayer has maintained all records required under this title and has cooperated with reasonable requests by the Secretary for witnesses, information, documents, meetings, and interviews; and (C) in the case of a partnership, corporation, or trust, the taxpayer is described in section 7430(c)(4)(A)(ii). Subparagraph (C) shall not apply to any qualified revocable trust (as defined in section 645(b)(1)) with respect to liability for tax for any taxable year ending after the date of the decedent’s death and before the applicable date (as defined in section 645(b)(2)). (3) CoordinationParagraph (1) shall not apply to any issue if any other provision of this title provides for a specific burden of proof with respect to such issue.
(b) Use of statistical information on unrelated taxpayersIn the case of an individual taxpayer, the Secretary shall have the burden of proof in any court proceeding with respect to any item of income which was reconstructed by the Secretary solely through the use of statistical information on unrelated taxpayers.
(c) PenaltiesNotwithstanding any other provision of this title, the Secretary shall have the burden of production in any court proceeding with respect to the liability of any individual for any penalty, addition to tax, or additional amount imposed by this title.