This Article explores the extent to which statutory periods of limitation in the Code are properly viewed as jurisdictional restrictions on the authority of the Tax Court. Starting in the mid-2000s, the Supreme Court began thinking about jurisdictional time limits in a new way. Applied of this new thinking to tax limitation periods has been limited and there is not comprehensive treatment of how this new thinking should apply the the Tax Code. This Article considers how the Supreme Court’s new thinking should apply to four time periods in the Code. Three govern access to the Tax Court: the period in section 6213 for contesting a Notice of Deficiency; the periods in sections 6320 and 6330 for contesting the outcome of an IRS Collection Due Process (CDP) hearing; and the period in section 6015(e) for contesting a denial of innocent spouse relief. The fourth is the two-year period in section 6532(a)(1) to file a suit for refund of taxes in either federal district court or the Court of Federal Claims. The Article first explains the Supreme Court’s new thinking. The Article next sets up the procedural contexts in which the four limitations periods appear. Then it analyzes each of the four periods. The Article concludes that for the deficiency and CDP time periods the new thinking leads to different conclusions from existing lower court precedents, which are now unlikely to survive Supreme Court scrutiny. In contrast, recent opinions about section 6015(e) have reasonably applied the new thinking in typing that limitations period as jurisdictional. Finally, a straightforward analysis of section 6532(a)(1) under the new thinking reveals it to be a plain-vanilla, claims-processing rule, contrary to past court decisions. Keywords: Jurisdiction, Tax Court, Refunds, claims processing, limitation periods, statute of limitations, limitations, Collection Due Process, CDP, Innocent Spouse, spousal relief, deficiency, 6213, 6330, 6015, 6532