Short answer
Letter 525 is the IRS’s general 30-day letter, usually sent after an audit by mail. It encloses the audit report, Form 4549, showing the proposed changes. Generally within 30 days of the letter date you can sign and agree, send more proof, or request Appeals. If you don’t respond, the IRS sends a notice of deficiency.
Key takeaways
- Letter 525 proposes audit changes; it is not a bill and nothing is assessed until you agree or the deadlines pass.
- You generally have 30 days from the letter date; for mail audits the IRS can ordinarily add 30 days on a first request.
- Disputes of $25,000 or less per period can use Form 12203 or a short statement; larger ones need a formal protest.
- No response leads to Letter 3219, the notice of deficiency, and a 90-day Tax Court deadline the IRS cannot extend.
What Letter 525 is
Letter 525 is the IRS’s “General 30-Day Letter.” The IRS Independent Office of Appeals says you get it “with a computation report of proposed adjustments to your tax return,” and that it “outlines your options if you don’t agree.” The Taxpayer Advocate Service (TAS) says that “generally, Letter 525 is issued if your audit was conducted by mail,” while Letter 915 is used after an in-person audit.
It is sent by the IRS campus units that run mail audits, under IRM 4.19.13. A secure messaging version, Letter 525-T, replaces it for taxpayers invited to reply online. It is a proposal, not a bill: nothing is assessed until you agree or the notice of deficiency process runs its course.
| 30-day letter | Usually follows |
|---|---|
| Letter 525 | An audit by mail |
| Letter 915 | An office (in-person) audit |
| Letter 950 | An unagreed field audit |
The choices are the same for all three; our 30-day letter guide compares them.
Why you got Letter 525
TAS says you receive a 30-day letter “because the IRS completed an examination of your tax return” and found that changes are necessary. In a mail audit that usually happens one of three ways:
- You answered the first letter, but not fully. If your reply to a Letter 566 did not support every item, the manual tells examiners to send Letter 525 with Form 4549 and explain “why the information is insufficient and what information is still needed” (IRM 4.19.13.11.1).
- You didn’t answer the first letter. After the waiting period, the IRS issues Letter 525 with the report (IRM 4.19.13.13).
- It was the first letter. Some IRS programs use Letter 525 with Form 4549 as the opening contact (IRM 4.19.20).
A CP2000 also proposes changes, but it is an income-matching notice, not an audit report.
What comes with Letter 525
When Letter 525 follows an unanswered first letter, the IRS manual lists the package as (IRM 4.19.13.13):
- Letter 525 itself, with the response date, contact number and your options.
- The proposed examination report, Form 4549, Report of Income Tax Examination Changes. It has a signature line. Read it with our guide to Form 4549.
- Form 886-A, Explanation of Items, or a form specific to the program, explaining each disallowed item. See Form 886-A.
- Publication 3498-A, The Examination Process (Audits by Mail).
- Form 14817, Reply Cover Sheet for Exam Correspondence.
TAS says the letter and report “should identify the specific items the examiner is proposing be adjusted and provide an explanation as to why.” If an item has no explanation, call the number on the letter and ask.
The 30-day deadline
TAS says that “generally, you must request an Appeals conference within 30 days from the date of your letter.” The Appeals office gives the same window for filing a protest. Count from the date printed on the letter, not the day it arrived, and use the response date on the letter if it differs.
- More time. TAS says to “call the number on the letter before the due date to ask for additional time.” For mail audits the IRS audits page says it “can ordinarily grant you a one-time automatic 30-day extension”; fax or mail the request. The IRS manual names Letter 525 among the letters where the first request adds 30 days to the original due date (IRM 4.19.13.11.7).
- The statute catch. If 180 days or less remain on the assessment statute, the manual says no extension is granted unless you agree to extend the statute. Appeals generally needs at least 365 days left when it receives a case (IRM 4.10.8.12), so the IRS may ask you to sign Form 872 before it forwards an appeal.
Your options
| Option | How | What happens next |
|---|---|---|
| Agree with everything | Sign and return Form 4549, with payment if you can | The IRS assesses the tax and bills any unpaid balance; you give up Appeals for those items |
| Send more proof | Mail, fax or upload copies with an explanation by the due date | The examiner reviews; if proof is still short, you may get Letter 692 with a revised or unchanged report, or a notice of deficiency |
| Talk to the examiner’s manager | Ask for an informal conference before the response date | The manager may resolve the issue; Appeals rights are kept if you still ask in time |
| Request Appeals | Written request with your reasons: Form 12203 or a short statement if each period is $25,000 (IRS.gov, 2026) or less; otherwise a formal written protest | The file goes to the IRS Independent Office of Appeals, which contacts you |
| Do nothing | None | Letter 3219, the notice of deficiency |
You can also mix them: agree with the items you can’t support and appeal the rest. TAS says the request for Appeals must be in writing and “include your reasons for disagreeing.” Templates: small case request letter and formal protest letter. For help deciding, see agree or appeal.
How to respond to Letter 525
- Find the response date on the letter and calendar a reminder a week before it.
- Compare each adjustment with your records. Go line by line through Form 4549 and the explanation. Mark each item agree or disagree.
- Gather proof for the disputed items. Send only copies. Publication 3498-A says that if you can’t verify an amount, “provide an explanation of the issue and how the amount was determined.” See missing records.
- Put the package together. Start with Form 14817 if it was enclosed, then a short cover letter listing the letter date, tax year and each enclosure (cover letter template). Add your Appeals request if you are asking for one.
- Send it to the address or fax number on the letter, not to Appeals. Use delivery confirmation for mail; put your name and Social Security number on each faxed page.
- Keep copies and proof of delivery, and watch your mail for the next letter.
Publication 3498-A says not to sign the agreement page if you “disagree or plan to appeal.”
What happens next
- If you agree. The tax is assessed and you get a bill, such as a CP14. Interest runs from the return’s due date at the federal short-term rate plus 3 percentage points, reset quarterly (7% (IRS.gov, Jul-Dec 2026) now). Publication 3498 says that if the bill is under $100,000 (IRS.gov, 2026) and you pay within 21 calendar days, no more interest or penalties are added. Can’t pay? See options when you can’t pay an audit bill.
- If you request Appeals. The examiner forwards the case and Appeals contacts you. Publication 3498-A says Appeals usually holds the conference by phone or correspondence, and that substantial new documents send the case back to the examiner.
- If there is no agreement or no reply. The IRS sends Letter 3219 by certified mail. You have 90 days from its date (150 if addressed outside the United States) to petition the Tax Court, and Publication 3498-A says the IRS “cannot extend the time.” See notice of deficiency.
Interest keeps running while you dispute. Publication 3498-A says a deposit or advance payment stops it on the amount you pay.
Mistakes to avoid
- Signing to make it go away. The IRS manual says signing Form 4549 indicates you “do not wish to exercise appeal rights” for the adjustments.
- Mailing the appeal to the wrong office. Send it to the address on Letter 525.
- Holding back documents for Appeals. New evidence at Appeals generally sends the case back to the examiner and costs time.
- Arguing on moral, religious or constitutional grounds. Publication 3498-A says those can’t be appealed.
- Treating Letter 525 like a bill. Nothing is owed until it is assessed.
Doing it yourself, free help, and representation
A one- or two-item mail audit where you now have the missing record is often manageable alone. A representative adds more when you need a formal protest, business income or penalties are involved, or the IRS asks you to extend the statute.
- Low Income Taxpayer Clinics represent eligible taxpayers in audits and appeals for free or a small fee (find a clinic).
- Taxpayer Advocate Service: free help when an IRS problem causes financial difficulty, 877-777-4778 (IRS.gov, 2026).
- A representative under Form 2848. Publication 3498-A says only attorneys, CPAs and enrolled agents may represent you at an Appeals conference.
Global Gate Tax Relief offers a free consultation and, if it takes the case, quotes a flat fee upfront. No outcome is guaranteed. Request a free review of your Letter 525 or call 1-877-800-8180.
Frequently asked questions
It is the IRS’s General 30-Day Letter, usually sent after an audit by mail. It encloses Form 4549 showing the proposed changes and explains your options to agree, send more information or request an Appeals conference.
Generally 30 days from the date of the letter, or the response date printed on it. Call before the date if you need more time; for mail audits the IRS can ordinarily grant a one-time 30-day extension.
No. It proposes changes. Tax is assessed only if you sign the report or, if you don’t, after the notice of deficiency deadline passes without a Tax Court petition. Then the IRS sends a bill.
Yes. Send a written request with your reasons to the address on the letter before the due date. If each tax period’s proposed change is $25,000 or less, Form 12203 or a short statement is enough; otherwise file a formal written protest.
The IRS sends Letter 3219, a notice of deficiency. You then have 90 days from its date (150 if addressed outside the US) to petition the Tax Court, or the tax is assessed and billed.
Letter 525 is a proposal with an offer of Appeals review inside the IRS. Letter 3219 is the legal notice of deficiency that starts the Tax Court deadline. Letter 525 comes first.
Sources
- Taxpayer Advocate Service: Letter 525, General 30-Day Letter (updated 14 Jul 2026)
- IRS Independent Office of Appeals: Letters and notices offering an appeal opportunity (reviewed 16 Jul 2026)
- IRM 4.19.13, General Case Development and Resolution (effective 01-23-2026)
- IRM 4.19.20, Automated Correspondence Exam (ACE) Processing Overview
- IRM 4.10.8, Report Writing (08-28-2025)
- IRS: IRS audits (reviewed 17 Feb 2026)
- IRS Publication 3498-A, The Examination Process (Audits by Mail) (Rev. 5-2021)
- IRS Publication 3498, The Examination Process (Rev. 5-2025)
- IRS Publication 5, Your Appeal Rights and How to Prepare a Protest (Rev. 4-2021)
- 26 U.S.C. 6213, Restrictions applicable to deficiencies; petition to Tax Court
- IRS: Quarterly interest rates
- IRS: Low Income Taxpayer Clinics
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