You Just Got a 90-Day Letter From the IRS. Here's What It Means.

You opened your mailbox and found a certified letter from the IRS. The envelope contains something called a "Notice of Deficiency" or "Statutory Notice of Deficiency." The letter says you have 90 days to respond.

Your heart is racing. You're not sure what this means or what happens if you miss the deadline.

Take a breath. This guide explains exactly what a 90-day letter is, what your options are, and the critical mistakes you need to avoid.

What Is a 90-Day Letter?

A 90-day letter (also called a Notice of Deficiency, Statutory Notice of Deficiency, or your "ticket to Tax Court") is the IRS's formal notice that they believe you owe additional tax. Common versions include CP3219A and CP3219N.

This notice typically follows an IRS audit—whether a correspondence exam, office audit, or field audit. If you're still in the examination stage, see How To Respond to an IRS Audit for what to do before this letter arrives.

This isn't just another IRS notice. It's a legal document that gives you a specific right: the right to challenge the IRS's decision in US Tax Court without paying the disputed amount first.

That last part is important. If you want to fight the IRS in any other court (District Court or Court of Federal Claims), you must pay the full amount first, then sue for a refund. Tax Court is the only forum where you can dispute first, pay later.

The 90-Day Deadline Is Real

You have exactly 90 days from the date on the notice to file a petition with the US Tax Court. If the notice was sent to an address outside the United States, you have 150 days.

Neither the IRS nor the Tax Court can extend this deadline. In most of the country it is absolute. In the states covered by four federal appeals courts (the Second, Third, Sixth and Eighth Circuits), a late petition can be excused in rare cases, but if you try and fail, the Court enters a decision that you owe the full amount in the notice, which can rule out a later refund suit; see Where You Live Changes the Answer. For practical purposes, treat the deadline as absolute. If day 90 falls on a Saturday, Sunday, or legal holiday in the District of Columbia, you have until the next business day.

One thing that may ease your mind: during the 90-day window—and for as long as a Tax Court case is pending—the IRS cannot assess or collect the disputed tax. No levies, no wage garnishment, no seizures. This protection is automatic under IRC § 6213(a). Interest continues to accrue, but collection is paused.

If you miss this deadline, the IRS will assess the tax automatically, and except in the rare cases described above, you lose your right to challenge it in Tax Court. The main way back into court is to pay the full amount, file a refund claim with the IRS, and then sue for a refund in a different court. See You Missed the 90-Day Deadline. Now What? for what you can still do.

Your Three Options

Option 1: Agree with the IRS

If the IRS is correct, sign Form 5564 (included with your notice) and return it. The IRS will assess the tax, and you can set up a payment plan if needed.

Option 2: Try to Resolve It Without Court

You can contact the IRS during the 90-day period to provide additional information or documentation. If the IRS agrees with your position, they may withdraw or modify the notice.

Important: Contacting the IRS does not extend your 90-day deadline. If negotiations fail and you've run out of time, you have almost certainly lost your Tax Court option.

Option 3: File a Petition with the US Tax Court

If you disagree with the IRS—in whole or in part—and want to preserve your right to challenge their decision, you must file a petition with the Tax Court before the deadline. You don't have to disagree with everything; you can petition to dispute specific adjustments while accepting others.

If you worry that petitioning will invite the IRS to ask for more: it can ask, but it has to claim any increase in the case and prove it. Can the IRS Raise Your Bill in Tax Court? explains how that works, and what not filing costs.

You can file electronically through DAWSON (the Tax Court's online system) or mail a paper petition. An e-filed petition must reach the Court by 11:59 p.m. Eastern Time on the last day, so convert that to your own time zone. If you mail it, send it certified or registered mail at a post office counter and ask the clerk to postmark your receipt; see Proving Your Tax Court Petition Was Filed on Time. The filing fee is $60, though fee waivers are available for those who qualify. For a step-by-step walkthrough, see How To File Your Tax Court Petition.

Should You Represent Yourself?

Around 89% of Tax Court petitioners represent themselves (called "pro se"). You have the legal right to do this.

However, the statistics are sobering: pro se petitioners prevail in full or in part only about 12% of the time, compared to about 23% for represented taxpayers. Evidence preparation is one of the biggest factors—understanding the burden of proof and what documentation you need can significantly improve your chances.

Common mistakes pro se petitioners make:

• Missing procedural deadlines after filing
• Failing to communicate with IRS counsel before trial
• Showing up to trial with documents the IRS has never seen
• Not understanding what issues they need to prove

If your case involves $50,000 or less per year, you can elect "small case" procedures, which are less formal. The trade-off: you cannot appeal a small case decision.

Who Can Represent You?

Only two types of professionals can represent you in Tax Court:

1. Attorneys admitted to the Tax Court bar
2. US Tax Court Practitioners (USTCPs)—non-attorneys who have passed a special Tax Court examination

CPAs and Enrolled Agents cannot represent you in Tax Court unless they also hold the USTCP credential. There are fewer than 300 USTCPs in the entire country.

If you cannot afford representation, Low Income Taxpayer Clinics (LITCs) may be able to help for free if your income is below 250% of the poverty line and your dispute is under $50,000.

What Happens After You File?

• The IRS has 60 days to respond to your petition
• Your case will typically be assigned to IRS Appeals for settlement discussions
• Most (76%) of Tax Court cases settle before trial
• If you don't settle, you'll receive a trial date (usually 5+ months out)
• The first day of trial is called the "calendar call" where the judge reviews pending cases

For a detailed walkthrough of what to expect, see What Happens After You File Your Tax Court Petition.

The Bottom Line

A 90-day letter is serious, but it's not the end of the world. You have options. The most important thing is to understand your deadline and make a deliberate choice before it passes.

Don't ignore the letter. Don't assume someone else will handle it. And don't wait until day 89 to figure out what to do.

This article is for informational purposes only and does not constitute legal or tax advice. For advice specific to your situation, consult a qualified tax professional or attorney.