IRS Notices
Letter 531 Notice of Deficiency: What It Means, Your Deadline, and What to Do (2025)
The short answer: Letter 531 is the IRS notice of deficiency sent after an audit. It's the official "90-day letter." It says the IRS has decided you owe more tax and gives you 90 days from the date on the letter to file a petition with the U.S. Tax Court before the IRS can assess and bill the amount.
⏱ Your deadline: the date printed on the letter to file a U.S. Tax Court petition — 90 days (or 150 days if the letter is addressed to you outside the United States). This deadline is strict and cannot be extended. Count from the letter date, not the day you opened the envelope.
Why you got Letter 531
You received Letter 531, the notice of deficiency, because the IRS audited a tax return with your name on it and decided you owe more than you reported. If you didn't reach an agreement during the audit — or never responded to the audit letters — the IRS issues this letter to make its proposed changes official. The letter shows the tax year, the extra tax (the "deficiency"), and any penalties and interest that come with it (the IRS explains the document at Understanding your Letter 531).
This letter is the IRS's last step before it can legally charge you. By law, the IRS usually can't bill you for audit changes until it sends a notice of deficiency and gives you a chance to fight it in court. That's why Letter 531 matters so much — it opens, and closes, a one-time window.
What happens if you ignore Letter 531
The 90-day clock runs whether or not you act. If you let it expire, the IRS assesses the deficiency, sends a bill, and your case rolls into the automated collection sequence. From there the escalation is predictable:
- Letter 531 (notice of deficiency) — your 90-day window to petition Tax Court. You are here.
- CP22 / first balance-due bill — after the 90 days, the audit change is assessed and you get a bill for the new total.
- CP501 / CP503 — reminder notices. Still bills, but interest and the late-payment penalty keep stacking each month.
- CP504 — Notice of Intent to Levy. The IRS can take your state refund, and a federal tax lien becomes likely.
- LT11 / Letter 1058 — Final Notice of Intent to Levy. After 30 days the IRS can garnish wages and levy bank accounts.
The single biggest mistake is treating Letter 531 like just another bill you can deal with later. Once the 90 days pass, you lose the right to challenge the amount in Tax Court without first paying it in full. Acting inside the window keeps every door open.
First: confirm the letter is real and read it closely
A genuine Letter 531 arrives by mail, usually certified, and references a specific audited year. Before you do anything, take ten minutes to check it:
- Match it to the audit. Does the tax year and the adjustment line up with the audit letters you already received? Pull those records together.
- Log into your IRS online account to see the year, balance, and any prior notices on file.
- Note the petition date. The exact "last day to petition Tax Court" is printed near the top. That date controls everything.
- Screen for scams. A real notice of deficiency never comes by email or text and never demands gift cards, wire transfers, or payment apps. If you're unsure, our guide on how to tell if an IRS letter is real walks through every check.
Your options after a Letter 531 notice of deficiency
You have more than two choices, and the right one depends on whether you disagree with the audit, agree but can't pay, or have new documents:
- File a U.S. Tax Court petition. If you believe the IRS is wrong, this is the most powerful move — and you don't have to pay first. The filing fee is small, and many cases settle with IRS Appeals before ever reaching a judge. See the basics in our guide to the 90-day letter and Tax Court petition, and file directly through the U.S. Tax Court.
- Agree and sign. If the changes are correct, you can sign the waiver (Form 5564) enclosed with the letter so the tax is assessed sooner and interest stops building on a fight you won't win.
- Provide missing information. If the audit decided against you because documents never reached the examiner, gather them now. After assessment, audit reconsideration lets you reopen the matter with the proof the IRS never saw.
- Plan for the balance. If you'll owe regardless, you can set up an installment agreement, request hardship status, or look at penalty relief once the amount is assessed. The IRS payment plans page shows the options.
One honest warning: a notice of deficiency is closely related to the CP3219A notice of deficiency sent in document-matching (CP2000) cases. The 90-day rule is the same. Anyone promising to make the whole bill disappear for "pennies on the dollar" before they've reviewed your finances is selling you something — not giving you a plan.
How to respond, step by step
- Find the petition deadline printed on the letter and put it on your calendar in red. That date is your line in the sand.
- Decide if you disagree. Compare the audit changes to your records. If the IRS is wrong — or you have proof it didn't consider — you have a real case.
- If you disagree, file a Tax Court petition before the 90 days end. This protects your rights even while you keep talking with the IRS.
- If you agree, sign the enclosed waiver to stop interest from growing on an amount you accept.
- If the deadline already passed, request audit reconsideration with new documents, or pay and file a refund claim — you still have paths, just different ones.
- If the numbers are large or confusing, get a professional review before the window closes. The order you handle this in — court, then balance, then penalties — changes what you ultimately pay.
Holding a Letter 531 right now?
The 90-day clock is already running. Send us a photo of the letter and an experienced tax professional will tell you exactly where you stand and what your options are — free, confidential, no pressure.
Letter 531 questions, answered
Is Letter 531 the same as the 90-day letter?
Yes. Letter 531 is a statutory notice of deficiency, which tax professionals call the 90-day letter. It gives you 90 days from the date on the letter (150 days if it's addressed to you outside the United States) to file a petition with the U.S. Tax Court before the IRS can assess and bill the tax.
What happens if I ignore Letter 531?
If you do nothing, after 90 days the IRS formally assesses the deficiency, sends a bill, and starts its collection sequence. You lose the right to challenge the amount in Tax Court without first paying it. Penalties and interest keep growing, and the notices that follow lead to liens and levies.
Can I still fix things if the 90 days already passed?
Often, yes. Once the deficiency is assessed you can request audit reconsideration if you have new information or documents the audit never saw, file Form 843 or pay and file a refund claim, or amend the return. You can also set up a payment plan, hardship status, or pursue other relief on the balance.
Do I have to pay the tax to file a Tax Court petition?
No. The whole point of Letter 531 and the 90-day window is that you can dispute the amount in U.S. Tax Court before paying. The filing fee is small. If you miss the 90 days, you generally must pay the tax first and then sue for a refund in a different court.
How do I know Letter 531 is real and not a scam?
A real Letter 531 arrives by postal mail, usually certified, never by email or text. It references a specific tax year and audit and explains your Tax Court rights. You can verify the balance by logging into your account at IRS.gov. The IRS never demands gift cards, wire transfers, or payment apps.
This guide is general information, not tax or legal advice for your specific situation. Eligibility for IRS programs depends on individual facts and circumstances; no outcome is guaranteed.