26 U.S.C. § 7481

(a) Reviewable decisions Except as provided in subsections (b), (c), and (d), the decision of the Tax Court shall become final— (1) Timely notice of appeal not filed Upon the expiration of the time allowed for filing a notice of appeal, if no such notice has been duly filed within such time; or (2) Decision affirmed or appeal dismissed (A) Petition for certiorari not filed on time Upon the expiration of the time allowed for filing a petition for certiorari, if the decision of the Tax Court has been affirmed or the appeal dismissed by the United States Court of Appeals and no petition for certiorari has been duly filed; or (B) Petition for certiorari denied Upon the denial of a petition for certiorari, if the decision of the Tax Court has been affirmed or the appeal dismissed by the United States Court of Appeals; or (C) After mandate of Supreme Court Upon the expiration of 30 days from the date of issuance of the mandate of the Supreme Court, if such Court directs that the decision of the Tax Court be affirmed or the appeal dismissed. (3) Decision modified or reversed (A) Upon mandate of Supreme Court If the Supreme Court directs that the decision of the Tax Court be modified or reversed, the decision of the Tax Court rendered in accordance with the mandate of the Supreme Court shall become final upon the expiration of 30 days from the time it was rendered, unless within such 30 days either the Secretary or the taxpayer has instituted proceedings to have such decision corrected to accord with the mandate, in which event the decision of the Tax Court shall become final when so corrected. (B) Upon mandate of the Court of Appeals If the decision of the Tax Court is modified or reversed by the United States Court of Appeals, and if— (i) the time allowed for filing a petition for certiorari has expired and no such petition has been duly filed, or (ii) the petition for certiorari has been denied, or (iii) the decision of the United States Court of Appeals has been affirmed by the Supreme Court, then the decision of the Tax Court rendered in accordance with the mandate of the United States Court of Appeals shall become final on the expiration of 30 days from the time such decision of the Tax Court was rendered, unless within such 30 days either the Secretary or the taxpayer has instituted proceedings to have such decision corrected so that it will accord with the mandate, in which event the decision of the Tax Court shall become final when so corrected. (4) Rehearing If the Supreme Court orders a rehearing; or if the case is remanded by the United States Court of Appeals to the Tax Court for a rehearing, and if— (A) the time allowed for filing a petition for certiorari has expired and no such petition has been duly filed, or (B) the petition for certiorari has been denied, or (C) the decision of the United States Court of Appeals has been affirmed by the Supreme Court, then the decision of the Tax Court rendered upon such rehearing shall become final in the same manner as though no prior decision of the Tax Court has been rendered. (5) Definition of “mandate” As used in this section, the term “mandate”, in case a mandate has been recalled prior to the expiration of 30 days from the date of issuance thereof, means the final mandate. (b) Nonreviewable decisions The decision of the Tax Court in a proceeding conducted under section 7436(c) or 7463 shall become final upon the expiration of 90 days after the decision is entered. (c) Jurisdiction over interest determinations (1) In general Notwithstanding subsection (a), if, within 1 year after the date the decision of the Tax Court becomes final under subsection (a) in a case to which this subsection applies, the taxpayer files a motion in the Tax Court for a redetermination of the amount of interest involved, then the Tax Court may reopen the case solely to determine whether the taxpayer has made an overpayment of such interest or the Secretary has made an underpayment of such interest and the amount thereof. (2) Cases to which this subsection applies This subsection shall apply where— (A) (i) an assessment has been made by the Secretary under section 6215 which includes interest as imposed by this title, and (ii) the taxpayer has paid the entire amount of the deficiency plus interest claimed by the Secretary, and (B) the Tax Court finds under section 6512(b) that the taxpayer has made an overpayment. (3) Special rules If the Tax Court determines under this subsection that the taxpayer has made an overpayment of interest or that the Secretary has made an underpayment of interest, then that determination shall be treated under section 6512(b)(1) as a determination of an overpayment of tax. An order of the Tax Court redetermining interest, when entered upon the records of the court, shall be reviewable in the same manner as a decision of the Tax Court. (d) Decisions relating to estate tax extended under section 6166 If with respect to a decedent’s estate subject to a decision of the Tax Court— (1) the time for payment of an amount of tax imposed by chapter 11 is extended under section 6166, and (2) there is treated as an administrative expense under section 2053 either— (A) any amount of interest which a decedent’s estate pays on any portion of the tax imposed by section 2001 on such estate for which the time of payment is extended under section 6166, or (B) interest on any estate, succession, legacy, or inheritance tax imposed by a State on such estate during the period of the extension of time for payment under section 6166, then, upon a motion by the petitioner in such case in which such time for payment of tax has been extended under section 6166, the Tax Court may reopen the case solely to modify the Court’s decision to reflect such estate’s entitlement to a deduction for such administration expenses under section 2053 and may hold further trial solely with respect to the claim for such deduction if, within the discretion of the Tax Court, such a hearing is deemed necessary. An order of the Tax Court disposing of a motion under this subsection shall be reviewable in the same manner as a decision of the Tax Court, but only with respect to the matters determined in such order.