Of all the mail the IRS sends, the Notice of Deficiency is the one where the deadline is everything. It says the IRS has determined you owe more tax, and it gives you 90 days to petition the United States Tax Court - the only court in America where you can fight the bill before paying it. Day 91 is too late forever. No extensions, no good-cause exceptions, no mercy for the envelope that sat in a pile. The clock runs from the date on the notice, not the date you opened it.
What the Petition Actually Does
Filing blocks the IRS from assessing the disputed tax and moves your case out of the hands of whoever decided against you - typically into IRS Appeals and Chief Counsel, who evaluate it under the hazards-of-litigation standard. Issues that were brick walls during the audit become negotiable when a judge might rule on them, which is why the overwhelming majority of petitioned cases settle without trial. The petition is less a declaration of war than the price of admission to a real negotiation.
Check the Notice Itself
Deficiency notices contain errors worth finding: income attributed to you that belongs to someone else, missing basis on sales, disallowed items with available proof, penalties with defenses. If your notice came from an audit you never participated in - mail you never received, an exam that ran without you - the proposed numbers are often built on the worst assumptions and collapse under actual documentation. For disputes of $50,000 or less per year, the simplified small-case procedures make the court genuinely accessible, though the election trades away appeal rights and deserves a deliberate choice.
Count the Days Today
Find the date on the notice and count 90 days forward right now. If you are inside the window, you have leverage and options. If the deadline is close, a protective petition can be filed quickly while the real work happens after. I am admitted to the Tax Court, and these notices are the most time-sensitive thing clients ever send me. Send yours today.