A Notice of Deficiency — often called a "90-day letter" or a statutory notice — is the IRS's formal declaration that you owe more tax than you reported. It is not a bill you simply pay or ignore. It is a legal document that starts a clock: you have exactly 90 days from the date on the notice to file a petition with the United States Tax Court, and that petition is the only way to challenge the IRS's determination before paying the disputed amount. Let the 90 days lapse and the IRS assesses the tax, the deficiency becomes final, and your options shrink to paying first and suing for a refund later.
The Tax Court petition is a powerful and underused right. It costs $60 to file, you don't need to pay the tax to get in the door, and for disputes of $50,000 or less per year there's a streamlined "small tax case" track designed for taxpayers without a lawyer. The catch is the deadline. The 90-day window is statutory — set by Congress in IRC Section 6213 — and the courts enforce it strictly. This is the one tax deadline where being a day late generally means losing the right entirely.
What a Notice of Deficiency actually is
The Notice of Deficiency is the IRS's ticket to court — and yours. Before the IRS can assess most income, estate, or gift tax deficiencies, it is legally required to send you this notice and give you the chance to petition the Tax Court. That's why it's sometimes called the taxpayer's "ticket to the Tax Court." It follows earlier correspondence (an examination report, a 30-day letter, sometimes an Appeals conference) and it means the informal stage is over.
Two things on the notice matter most: the amount the IRS says you owe and the last date to file a petition, which is printed right on the letter. Do not rely on counting 90 days yourself and do not rely on when you happened to open the envelope — the clock runs from the date on the notice, not the date you received it.
Every valid Notice of Deficiency states the exact last day to file a Tax Court petition. Since a 2015 law change, if that date is stated on the notice, the IRS is bound by it. Use that printed date as your deadline. If the notice was mailed to an address outside the United States, the window is 150 days instead of 90. Either way, the date on the letter governs — count from there, not from receipt.
The 90-day deadline is nearly absolute
For decades the 90-day filing period was treated as a hard jurisdictional wall: file on day 91 and the Tax Court had no power to hear your case, full stop. Recent litigation has softened the edges slightly in narrow circumstances, but the safe and correct assumption for every taxpayer is that the deadline is real and unforgiving. Do not plan around exceptions.
Note the date on the notice
Find the printed last-file date on the Notice of Deficiency the moment it arrives. That date, not the postmark or the day you opened it, is your deadline.
Count the mailing method as filing
A petition mailed by the last day via U.S. mail or an IRS-designated private carrier is treated as filed on the postmark date under the timely-mailing rule (IRC Section 7502). Electronic filing through the court's DAWSON system is timestamped in the court's time zone.
Don't wait for Appeals to call back
Ongoing settlement talks do NOT pause the 90 days. If the deadline is approaching and nothing is resolved, file the petition to preserve your rights — you can still settle afterward.
File even if your case isn't fully built
The petition is a short document that starts the case. You do not need every argument perfected to file it; you develop the case after filing. Filing on time is what matters.
The single most common — and most avoidable — way to lose a strong tax dispute is to let the 90 days run while waiting, negotiating, or gathering documents. File first. Perfect the case second.
Tax Court vs. paying first and suing for a refund
The Tax Court is one of three federal forums for tax disputes, and it is the only one you can use without paying the disputed tax up front. That single feature is why most individual taxpayers choose it.
U.S. Tax Court (petition route)
- File within 90 days of the Notice of Deficiency
- You do NOT pay the disputed tax first
- Judges are tax-law specialists
- Small tax case (S) track for disputes ≤ $50,000/year
- Most cases settle before trial with IRS counsel
District Court / Court of Federal Claims (refund route)
- Pay the tax in full first, then file a refund claim
- Sue only after the claim is denied or six months pass
- A jury is available in District Court
- No dollar cap, but no simplified small-case track
- Used when you'd rather pay and fight than petition
For the great majority of individuals and small businesses, the petition route wins on cash flow alone — you keep your money in your pocket while the dispute is decided. The refund route makes sense mainly when you've already paid or when a specific procedural advantage (like a jury) matters to your facts.
Small tax case (S) vs. regular case
When you file, you elect either a regular case or a small tax case (an "S" case). The S case is a simplified procedure available whenever the disputed tax is $50,000 or less for any one tax year. It's built for taxpayers representing themselves.
| Feature | Small tax case (S) | Regular case |
|---|---|---|
| Dollar limit | $50,000 or less per year | No limit |
| Procedure | Informal, relaxed rules of evidence | Formal Tax Court rules apply |
| Representation | Self-representation common | Often uses admitted counsel |
| Right to appeal | No — decision is final for both sides | Yes — appealable to a U.S. Court of Appeals |
The S-case tradeoff is straightforward: you get a faster, friendlier, less expensive process, but you give up the right to appeal an unfavorable decision. Neither you nor the IRS can take an S-case ruling higher. For a genuinely close question of law where an appeal could matter, a regular case may be worth the added formality — but for most factual disputes under the $50,000 threshold, the S case is the right tool.
Filing the petition, step by step
The mechanics are more approachable than most people expect. The court has a fillable petition form and an electronic filing system (DAWSON) built with self-represented taxpayers in mind.
- Complete the Tax Court petition form and check the box electing regular or small tax case (S)
- Attach a copy of the Notice of Deficiency (redact your Social Security number as the court instructs)
- State plainly which items you disagree with and why — you don't need legalese
- Pay the $60 filing fee, or request a fee waiver if you can't afford it
- File on time via DAWSON e-filing, U.S. mail, or an IRS-designated private delivery service
- Keep proof of the filing date — a postmark, private-carrier receipt, or DAWSON confirmation
After you file, your case is assigned to an IRS attorney (Chief Counsel), not the auditor you dealt with before. That's often good news: Counsel can settle, and the overwhelming majority of Tax Court petitions are resolved by agreement before ever reaching a courtroom. Filing the petition frequently improves your negotiating position rather than starting a fight.
Treat the Notice of Deficiency as a countdown, not a bill. Read the last-file date off the notice, and file your Tax Court petition on or before that date — 90 days, or 150 if you're abroad. Petitioning is the only way to dispute the IRS without paying first; it costs $60; and disputes of $50,000 or less per year qualify for the simplified small tax case track, which trades the right to appeal for a faster, informal process. File on time even if your case isn't fully built, because most petitions settle with IRS Counsel afterward. The one unrecoverable mistake is letting the 90 days lapse.
Got a 90-day letter? The clock is already running.
Talk to our team about your situation — if you've received a Notice of Deficiency, the 90-day deadline is real, so don't wait to get help understanding your options.
Talk to a tax proSources
- IRS — Understanding Your CP3219A Notice (Notice of Deficiency)
- Internal Revenue Code Section 6213(a) — Restrictions on assessment; petition to Tax Court
- Internal Revenue Code Section 7502 — Timely mailing treated as timely filing
- U.S. Tax Court — Petition Kit and Rules of Practice and Procedure (Rules 20 and 170–174, small tax cases)
- U.S. Tax Court — DAWSON electronic filing system and Guidance for Petitioners
Frequently asked questions
You have 90 days from the date printed on the Notice of Deficiency — 150 days if the notice is addressed to you outside the United States. The notice itself states the last day to file. The deadline is set by statute (IRC Section 6213) and generally cannot be extended.
No. The US Tax Court is the only forum where you can dispute a deficiency without first paying it. If you pay the tax and then sue for a refund, that case goes to a US District Court or the Court of Federal Claims instead — after you've already paid.
An S case is a simplified Tax Court procedure available when the disputed amount is $50,000 or less for any single tax year. Hearings are informal, the rules of evidence are relaxed, and you can represent yourself — but an S-case decision cannot be appealed by either side.
The filing fee is $60, payable when you file the petition. You can request a waiver of the fee if you can't afford it. There is no requirement to hire a representative, though most taxpayers with meaningful amounts at stake use a CPA, enrolled agent admitted to practice, or a tax attorney.
