⚠️ Educational only. TaxPlain does not provide tax, legal, or financial advice. Letter 525 has a strict 30-day response deadline — consult a qualified tax professional before signing any agreement.
What this letter is
IRS Letter 525 is the General 30-Day Letter — the notice the IRS sends after completing a correspondence (mail) audit of your tax return. It tells you the audit is finished, explains what changes the IRS is proposing, and gives you 30 days to agree or push back.
This is not a final bill. Think of it as the IRS handing you a proposed grade on your return and asking: "Do you accept this, or do you want to argue your case?" The letter almost always arrives with Form 4549 (Report of Income Tax Examination Changes), which shows exactly what the auditor changed and how it affects your tax, penalties, and interest.
⏱️ Your deadline is 30 days
The clock starts from the date printed on the letter — not the date you opened it. You have 30 calendar days to agree, send supporting documents, or request an appeal with the IRS Office of Appeals. Missing this window means losing your right to an administrative appeal and waiting for a Notice of Deficiency (Letter 3219), which forces you into Tax Court to dispute.
Why the IRS sent this
✓ Most common reasons
Your return was selected for a correspondence audit — the IRS reviewed your records by mail and found items they want to change. Common triggers: large deductions, mismatched 1099 income, business expenses without adequate documentation, or credits the IRS couldn't verify.
↑ What the changes mean
The proposed adjustments may increase what you owe (additional tax plus penalties and interest), reduce a refund you expected, or in some cases result in a refund if the IRS found you overpaid. Form 4549 attached to the letter shows the exact dollar impact line by line.
What's included with the letter
Breaking down the package
Letter 525 is never sent alone. Here's what to look for in the envelope:
Letter 525 itself — Explains the audit results, your response options, and the 30-day deadline
Form 4549 — The examination report showing every proposed change to your return, recalculated tax, and any penalties or interest
Form 4549-A or 886-A — An explanation of each adjustment, telling you why the IRS disallowed or changed specific items
Agreement form — A waiver to sign if you agree with all proposed changes (do not sign until you've reviewed everything)
Publication 1 — Your Rights as a Taxpayer, outlining your protections during the process
Appeal instructions — How to request a hearing with the IRS Office of Appeals if you disagree
Your three options
What you can do
When you receive Letter 525, you have three paths. Doing nothing is effectively choosing option three — and it's the worst one.
Option 1 — Agree
If the IRS is correct, sign and return the agreement form included with the letter. The IRS will assess the additional tax and send a bill. You can pay in full or request an installment agreement.
Option 2 — Disagree & respond
Send a written response with supporting documentation by the deadline. Include receipts, bank statements, mileage logs, or whatever proves your original return was correct. You can also request an appeal to the IRS Office of Appeals.
⚠️ Option 3 — Do nothing (bad)
If you ignore the letter, the IRS will issue a Notice of Deficiency (Letter 3219) — a 90-day legal notice that removes your right to an administrative appeal. You'll then need to petition Tax Court to dispute, which is far more expensive and stressful than responding now.
What to do right now
Step one: find the date on the letter and count 30 calendar days forward — write that deadline down. Step two: open Form 4549 and read every proposed change line by line. Compare each adjustment against your original records. Step three: call a CPA or enrolled agent before signing anything — even if you think the IRS is right, a professional can often negotiate penalty abatement. If you disagree, gather your documentation and either mail a written protest or request an appeal before the deadline. You can call the number on the letter to request a short extension, but don't count on it — act as if 30 days is all you have.
How to appeal
Requesting IRS Office of Appeals
If you disagree with the audit results, you can request an independent review by the IRS Office of Appeals — a separate division that re-examines the case without the original auditor having the final say.
File a written protest — Send a letter explaining why you disagree, referencing specific line items on Form 4549, with supporting documents attached
Meet with Appeals — You may be offered a conference (by phone or in person) with an Appeals Officer who reviews both sides
No payment required upfront — Unlike Tax Court, you don't pay the disputed amount while Appeals considers your case
Most cases settle — Appeals frequently reaches a compromise between what you claimed and what the auditor proposed
Deadline is strict — Your protest must arrive within 30 days of the letter date. Missing it closes this path permanently
Common mistakes to avoid
⚠️ Signing too quickly
The agreement form looks simple — sign here, mail back. But once you sign, reversing the agreement is extremely difficult. Review Form 4549 carefully and compare every line to your records before agreeing to anything.
⚠️ Calling without responding
Calling the IRS to discuss the letter does not stop the 30-day clock. Only a signed agreement, written response, or formal appeal request counts as a response. Phone conversations alone change nothing legally.
⚠️ Sending docs without explanation
Dumping receipts in an envelope without a written explanation of why the IRS is wrong rarely works. Your response should reference specific Form 4549 line items and explain how your documentation supports your original return.
⚠️ Assuming it's fraud
Most Letter 525s result from documentation gaps or reporting differences — not accusations of cheating. A disallowed home office deduction because you lacked a written log is an audit adjustment, not a criminal investigation.
Questions to ask your tax professional
01Are the IRS's proposed changes on Form 4549 correct, or can we document that specific items should stand?
02Should I agree, respond with documentation, or file an appeal — and what's the best strategy for my dollar amount?
03Can any penalties be abated for reasonable cause even if the underlying tax adjustment is valid?
04What documentation do I need to gather before the 30-day deadline?
05If I agree with part of the changes but not all, can we negotiate a partial agreement?
06What happens if I miss the 30-day deadline — is Letter 3219 inevitable?
Frequently asked questions
Is Letter 525 the same as Letter 531?
They're both 30-day letters with the same purpose — giving you a chance to agree or appeal audit results. Letter 525 is sent after a correspondence (mail) audit. Letter 531 is sent after an in-person or office audit. The response options and deadlines are the same; only the audit type differs.
Does receiving Letter 525 mean I'm in trouble?
It means the IRS finished reviewing your return and wants to make changes — not that you're being criminally investigated. Most audit adjustments are civil matters about documentation or reporting differences. That said, the proposed changes are real and the 30-day deadline is strict, so take it seriously.
Can I get more time to respond?
You can call the number on the letter before the deadline and request an extension — the IRS sometimes grants additional time, especially if you need to gather records. But this is discretionary, not guaranteed. Never assume you'll get more time; start working on your response immediately.
What if the IRS owes me a refund instead of me owing them?
Sometimes an audit results in the IRS finding you overpaid — meaning you'd get additional money back. Letter 525 can propose changes in either direction. Read Form 4549 carefully: a negative "total amount due" means the IRS thinks they owe you.
What happens if I ignore Letter 525?
The IRS will issue a Notice of Deficiency (Letter 3219) — a formal legal notice giving you 90 days to petition Tax Court. You'll lose the simpler, cheaper option of resolving the dispute through IRS Appeals. Ignoring a 525 almost always makes things worse and more expensive.