Letter 531 is a statutory notice of deficiency. Petition the U.S. Tax Court by the exact date shown if you want prepayment review.
Editorially reviewed by the Law Offices of Darrin T. Mish, P.A.•Updated October 1, 2026
General information only, not legal advice. Using this page does not create an attorney-client relationship. This information may be incomplete or out of date and is provided without any guarantee; follow the instructions and deadline on your own notice. Full terms and disclaimer
Notice
Letter 531
Urgency
Critical
Deadline
90 days to petition Tax Court
Your first move
Notice of deficiency. File a Tax Court petition by the exact date shown if you want prepayment review.
Deadline calculator
Estimate your Letter 531 deadline
Estimate only. If your notice shows a specific respond-by date, that date controls. Some deadlines run from the mailing date, and a statewide holiday where the IRS office is located can also extend a deadline. Mail early, keep proof of mailing, and if a deadline matters, have a professional confirm it. Terms and disclaimer
See it explained
Letter 531 in plain English
Letter 531: what it means, in 30 secondsA 30-second overview from tax attorney Darrin T. Mish: what this notice is, the deadline, and your first move.
Letter 531 is a statutory notice of deficiency, often called a 90-day letter. It states the tax and penalties the IRS intends to assess and gives you a final date to petition the U.S. Tax Court without first paying the disputed amount.
The Date on the Letter Controls
The petition deadline is generally 90 days from the notice date, or 150 days when the notice is addressed outside the United States. Use the exact last date printed on the notice. Calling the IRS, sending documents, or asking for reconsideration does not extend that statutory deadline.
What to Do
Compare the proposed changes with the return and prior examination correspondence. If you disagree and want Tax Court review, make sure a valid petition is filed on time. You may continue trying to resolve the case administratively, but do not let those discussions consume the petition period.
If you've received Letter 531, call us at (813) 229-7100. A missed Tax Court deadline can eliminate prepayment review.
This letter has a clock on it. Don’t run it out alone.
Free consultation with Darrin T. Mish, a Tampa tax attorney licensed since 1993 and admitted to the U.S. Tax Court. Bring the letter.