IRS Letter 531: Notice of Deficiency — 90-Day Letter

You have 90 days to file a Tax Court petition — or the IRS's assessment becomes final.

Your deadline

90 days (150 days if addressed to a person outside the US) from notice date to file Tax Court petition

The 90-day deadline is jurisdictional — if you miss it, After 30 days, an equivalent hearing is still available for one year, without Tax Court review.

How soon to act: Critical

What this notice means

Letter 531 — commonly called the 90-Day Letter or Notice of Deficiency — is one of the most important and time-sensitive documents the IRS sends. It represents the end of the examination or underreporter process and the IRS's final proposed assessment before it becomes legally binding.

This letter gives you 90 days to petition the U.S. Tax Court for a redetermination of the deficiency. During this 90-day window, the IRS cannot assess or collect the proposed amount. If you file a Tax Court petition, assessment is further delayed while your case is litigated.

If the 90-day deadline passes without a petition, the IRS automatically assesses the full deficiency plus penalties. You can still pay the tax and then file a refund claim, but the Tax Court route — which allows you to fight the IRS without paying first — is permanently closed.

How it works

1
Calendar the 90-day deadline immediately — it is jurisdictional and cannot be extended
2
Contact a tax professional within the first week — building a Tax Court case takes time
3
Evaluate whether the IRS's position is correct — many deficiencies contain errors or omissions

Other options

If you agree with the proposed assessment, you can sign the waiver and pay without filing in Tax Court
If you partially agree, a Tax Court petition still allows for settlement negotiation

If you do nothing

Automatically assess the full proposed deficiency plus penalties after 90 days
Begin collection on the assessed amount including levy and lien action
Impose accuracy-related penalties of 20% of the underpayment
Add interest from the original due date of the return

Which sounds like you?

U.S. Tax Court Representation

File a petition within 90 days to formally challenge the deficiency

IRS Appeals & CDP Hearings

Even before Tax Court, the IRS Appeals Office can resolve many deficiencies

Audit Defense

Professional representation throughout the examination process

Penalty Abatement

Challenge accuracy-related penalties with reasonable cause

Common questions

What happens if I miss the 90-day Tax Court deadline?

The IRS automatically assesses the full proposed tax, penalties, and interest. After 30 days, an equivalent hearing is still available for one year, without Tax Court review. You can still pay and file a refund claim, but the burden of proof shifts to you in a different forum.

Does filing in Tax Court mean I have to go to trial?

Some cases reach agreement before trial and others do not. A timely, valid petition allows court review; settlement and trial outcomes depend on the facts and law.

Can I go to Tax Court without a lawyer?

Taxpayers can represent themselves (pro se) in Tax Court. However, for anything other than a small case (under $50,000), professional representation is strongly recommended.

What is the difference between a 30-Day Letter and a 90-Day Letter?

The 30-Day Letter (Letter 525) is the IRS's proposed audit adjustment — you can still appeal internally. The 90-Day Letter (Letter 531) is the final step — your only option is Tax Court or acceptance.