Letter 525 (the 30-Day Letter): How to Fight an Audit Report Before It Becomes a Bill

You have 30 days from the date printed on a Letter 525 to keep your case out of Tax Court and in front of an appeals officer who can settle it on hazards of litigation. Miss that window and your next letter is usually a Statutory Notice of Deficiency (the 90-day letter), which changes your options and your leverage. The 30-day letter is one of the most misread pieces of mail the IRS sends: clients treat it as a bill and either pay or panic. It is neither. It is a proposal you can still fight for free, inside the agency, before anyone assesses a dollar.

What is a Letter 525 (the 30-day letter)?

Letter 525 is the general 30-day letter the IRS issues at the end of an examination to transmit the examiner's proposed adjustments and tell you that you have 30 days to request a conference with the IRS Independent Office of Appeals. It arrives with a copy of the examiner's report — Form 4549 (Report of Income Tax Examination Changes) or Form 4605 — showing the proposed tax, penalties, and interest.

The examination version you receive can vary. Letter 525 (sometimes called the "general 30-day letter") is the common one; correspondence-audit cases sometimes get Letter 915, and specific programs use their own transmittals. What they share is the operative deadline: you have 30 days from the date on the letter, not from the date you open it, to respond.

The key point clients miss: nothing has been assessed yet. At the 30-day-letter stage the IRS is telling you what it proposes to do. You can agree, you can supply more information, or you can formally protest to Appeals. Doing nothing is itself a choice — it moves you toward the next stage.

What happens if you ignore the 30-day letter?

If you let the 30 days lapse without responding, the IRS generally issues a Statutory Notice of Deficiency under §6212 — the "90-day letter." That notice gives you 90 days (150 if addressed outside the United States) to petition the U.S. Tax Court under §6213(a) before the tax can be assessed.

So ignoring Letter 525 does not end your rights, but it narrows them and raises the stakes:

• You lose the cheapest, fastest forum. An Appeals conference is administrative, informal, and free. Tax Court is litigation.
• The clock gets rigid. The 90-day deadline in §6213(a) is jurisdictional — the Tax Court has repeatedly held it cannot be extended. Blow it and you generally must pay first, then sue for a refund in district court or the Court of Federal Claims.
• You still might land in Appeals anyway, because a docketed Tax Court case is usually routed to Appeals for settlement first. But you have spent leverage getting there.

In practice, the returns I have worked where the taxpayer waited out the 30-day letter "to think about it" almost always cost more — not because the position was worse, but because the informal fixes available at Appeals get harder once a case is docketed.

Should you go to Appeals or wait for the 90-day letter?

Go to Appeals on the 30-day letter when you have a genuine factual or legal dispute and want the cheapest path to resolution. Wait for the 90-day letter only in narrow situations — for example, when you need the Tax Court's prepayment forum and are prepared to litigate.

Appeals exists to settle cases based on the hazards of litigation — the probability the IRS would lose if the dispute went to court. An examiner cannot weigh that; an examiner applies the rules as written. An appeals officer can look at a 60/40 issue and settle it at roughly those odds. That is the entire value of the forum, and it is why substantiation-and-judgment cases (reasonable compensation, §162 business-purpose fights, penalty abatement, valuation) do well there.

	Appeals (30-day letter)	Tax Court (90-day letter)
Cost	Free	Filing fee, usually counsel
Formality	Informal conference	Litigation, rules of evidence
Can settle on hazards	Yes	Yes, but via Appeals or Counsel
Pay first?	No	No (petition before assessment)
Deadline	30 days, can request extension	90 days, jurisdictional, no extension

How do you write a protest to the 30-day letter?

For a proposed change over $25,000 for any tax period, you must file a formal written protest; for $25,000 or less you can use a small case request (a brief written statement), per the procedures in IRS Pub. 5 and Pub. 556. Either way it goes to the examiner's office, not directly to Appeals.

A formal protest under Pub. 5 needs to include:

1. Your name, address, and a daytime phone number.
2. A statement that you want to appeal the examination findings to Appeals.
3. A copy of the letter showing the proposed changes (the Letter 525), or the date and symbols from it.
4. The tax periods or years involved.
5. A list of each proposed change you disagree with and why.
6. The facts supporting your position on each issue.
7. The law or authority you are relying on.
8. A penalties-of-perjury statement, signed by you (specific language is set out in Pub. 5).

Two things I push clients on. First, lead with the facts and the substantiation you can actually prove — Appeals officers see thin assertions all day; documents move cases. Second, name your authority. If your position rests on §162(a), a specific reg, or a revenue ruling, cite it. A protest that argues "we think this is fair" concedes the hazards analysis before it starts.

Can you still submit new documents at this stage?

Yes — and often you should. The 30-day-letter window is frequently the first realistic chance to organize substantiation that was scattered or incomplete during the examination. If the examiner proposed disallowing deductions for lack of records under §6001, producing clean records now can resolve issues before Appeals ever weighs the law.

One caution: if you introduce significant new information or evidence that the examiner never saw, Appeals may return the case to Examination to consider it first (this is standard Appeals practice under the Internal Revenue Manual). That is not a penalty — it is procedure — but it can add months. Decide deliberately whether a document belongs in front of the examiner or the appeals officer.

Does interest keep running while you appeal?

Yes. Interest under §6601 continues to accrue on any underpayment during the entire appeals process — it does not pause because you are disputing the amount. The interest rate is set quarterly under §6621 and, for individual underpayments, is the federal short-term rate plus 3 percentage points.

That accrual is the real cost of a long appeal, and it drives a specific tactic: if you expect to owe some of the proposed amount regardless of outcome, you can make a deposit under §6603 to stop the running of interest on the portion you deposit while you continue to dispute it. Unlike a payment, a §6603 deposit can be returned to you if you prevail, and it stops interest in the meantime. For a five- or six-figure proposed deficiency that may sit in Appeals for a year, that is not a rounding error.

None of this is a substitute for advice on your specific facts, and outcomes depend on the record you can prove and the jurisdiction involved. If your case involves potential fraud exposure or criminal issues, stop and consult your attorney before you file anything.

Sources

• IRC §6212 (Notice of Deficiency)
• IRC §6213(a) (90-day / 150-day petition period; restriction on assessment)
• IRC §6001 (recordkeeping requirement)
• IRC §6601 (interest on underpayment)
• IRC §6621 (determination of interest rate)
• IRC §6603 (deposits made to suspend running of interest)
• IRC §162(a) (trade or business expenses)
• IRS Letter 525 (General 30-Day Letter); IRS Letter 915; IRS Letter 950
• Form 4549 (Report of Income Tax Examination Changes); Form 4605
• IRS Pub. 5 (Your Appeal Rights and How to Prepare a Protest If You Don't Agree)
• IRS Pub. 556 (Examination of Returns, Appeal Rights, and Claims for Refund)
• Internal Revenue Manual, Appeals procedures on new issues and new information