26 U.S. Code § 7483 - Notice of appeal
Review of a decision of the Tax Court shall be obtained by filing a notice of appeal with the clerk of the Tax Court within 90 days after the decision of the Tax Court is entered. If a timely notice of appeal is filed by one party, any other party may take an appeal by filing a notice of appeal within 120 days after the decision of the Tax Court is entered.
1969—Pub. L. 91–172 substituted references to notice of appeal for references to petition for review, and otherwise generally altered the section as to time for appeal and terminology in order to conform section to the form of the Federal Rules of Appellate Procedure.