IRS Audits
IRS Mail Audit: What to Expect, Your Deadline, and How to Respond (2025)
The short answer: an IRS mail audit (the IRS calls it a correspondence audit) is a letter asking you to prove one or two items on your tax return — a credit, a deduction, or income that didn't match. There's no in-person meeting. You mail back copies of your records, usually within 30 days, and the audit closes by mail. Most are narrow and fixable.
⏱ Your deadline: the date printed on the audit letter — almost always 30 days from the letter date. Respond by then, or call to request an extension before the date passes. Miss it and the IRS decides without you and issues a Notice of Deficiency (the 90-day letter) with extra tax, penalties, and interest.
What an IRS mail audit actually is
If you searched "irs mail audit what to expect," you're probably holding a letter and bracing for the worst. Take a breath. A mail audit is the smallest, most common type of IRS exam. It does not mean an agent is coming to your home. It means the IRS computer flagged something specific on one return and wants paper proof.
The letter usually arrives as an IRS Letter 566 or a CP75 notice. It names the tax year, lists the exact items under review, and includes a form or checklist showing what to send. Common triggers include the Earned Income Tax Credit, education or child-related credits, large charitable or business deductions, or income that didn't match a W-2 or 1099 the IRS received. You can read the IRS's own overview on the IRS audits page, and the EITC version at Understanding your CP75 notice.
One thing to know up front: a mail audit is different from a CP2000 notice. A CP2000 is an automated "your numbers don't match our records" letter, not a formal audit. A mail audit is an actual examination — but it's still handled entirely by letter.
What to expect, step by step
Here's the typical path a correspondence audit follows so nothing surprises you:
- The opening letter tells you which year and which items are being examined, and what records to send.
- You mail copies of the supporting documents — never originals — by the deadline.
- The IRS reviews what you sent. This can take weeks or months because of mail volume.
- You get a result: "no change" (you win, nothing owed), an adjustment you can agree to, or a proposed change you can dispute.
- If you disagree, the report explains how to appeal to the independent IRS Office of Appeals before anything becomes final.
What happens if you ignore it
Mail audits do not go away if you stay silent. The system is automated and moves on a schedule whether or not you answer. Here's the escalation:
- Audit letter (Letter 566 / CP75) — the request for documents. You are here. Nothing is owed yet.
- 30-day letter — a proposed adjustment with the auditor's findings and your right to appeal. The clock is running.
- Notice of Deficiency (CP3219A, the 90-day letter) — the IRS disallows the items and proposes extra tax. You have 90 days to petition the U.S. Tax Court.
- Assessment and collection — after 90 days the balance is final. Now you're getting bills like the CP14, then collection notices, and eventually levy power.
The takeaway: a mail audit you answer well can close with zero change. A mail audit you ignore turns into a tax bill you can't easily argue with later. Responding is almost always the cheaper path.
How to respond, step by step
- Read the letter twice and find the deadline. Note the exact items under review and the response date. Confirm the letter is real — the IRS contacts you by mail, never by surprise phone call, text, or email demanding payment.
- Pull the records that match each item. For a deduction, that's receipts, bank or credit-card statements, mileage logs, or canceled checks. For a credit like the EITC, that's proof of residency, birth certificates, school or medical records showing the child lived with you.
- Make a simple cover sheet. List each item the IRS questioned, and next to it name the documents you're sending as proof. Auditors review hundreds of files — clarity speeds your case.
- Send copies, not originals. Mail to the address on the letter (use tracked mail and keep the receipt), or upload through the IRS Documentation Upload Tool if the letter gives you an access code.
- Need more time? Call the number on the letter before the deadline and ask for an extension, or request one in writing. The IRS often grants it if you ask early.
- If you're missing records, reconstruct what you can — request statements from your bank, employer, or charity. You can still rebuild support after the fact; see our guide on how to handle taxes without records.
Got an audit letter and not sure what to send?
Send us a photo of it. An experienced tax professional will read exactly what the IRS is questioning, tell you which documents will close it, and help you respond on time — free, confidential, no pressure.
A worked example
Say the IRS audits your $9,000 charitable deduction. You panic — but you have your year-end giving statements from the church and two thrift-store donation receipts. You copy them, write a one-page cover sheet listing each donation, and mail it tracked. Weeks later you get a "no change" letter: the $9,000 stands, you owe nothing extra.
Now flip it. You ignore the letter. The IRS disallows the full $9,000. At a 22% tax bracket that's about $1,980 in extra tax, plus an accuracy penalty and interest that keeps growing. Same facts, very different ending — the only variable was whether you answered. That's why responding matters more than how strong your case feels.
How far back can the IRS audit?
Most mail audits look at a return filed in the last three years. The IRS generally has three years from the filing date to start an exam, but that window stretches to six years if you under-reported income by more than 25%, and there's no time limit at all for a return that was never filed or was fraudulent. Our full breakdown is here: how far back the IRS can audit.
If the audit already closed against you because you missed the deadline — and you now have the documents you couldn't find before — you may be able to reopen it through audit reconsideration. It's not guaranteed, but it's a real second chance.
IRS mail audit questions, answered
How long does an IRS mail audit take?
A correspondence audit can take anywhere from three to six months, and sometimes longer if mail crosses or documents need a second review. The IRS usually gives you 30 days to respond to each letter. Sending complete, organized records the first time is the single biggest thing that shortens the process.
What happens if I ignore an IRS mail audit?
If you don't respond, the IRS decides the audit without you and disallows the items in question. You'll receive a Notice of Deficiency (the 90-day letter) showing extra tax, penalties, and interest. After 90 days that amount becomes a legal bill and moves into collection — so silence is the most expensive option.
Does a mail audit mean I'm in trouble?
Not necessarily. A mail audit usually targets one or two specific items — a credit, a deduction, or income that didn't match a form the IRS received. It is the lowest-level type of audit. If you can document what you claimed, the audit can close with no change at all.
Can I get more time to respond to a mail audit?
Yes. Call the number on the letter before your deadline and ask for an extension, or send a written request. The IRS often grants more time if you ask before the due date. Don't wait until the deadline passes — once a Notice of Deficiency is issued, your options narrow.
What if I disagree with the mail audit result?
You can appeal. The audit report explains how to request a meeting with the IRS Office of Appeals, which is independent of the auditor. If you missed the deadline and the change is already on your account, you may be able to ask for audit reconsideration with the documents you originally lacked.
This guide is general information, not tax or legal advice for your specific situation. Eligibility for IRS programs depends on individual facts and circumstances; no outcome is guaranteed. If you need help, the Taxpayer Advocate Service is a free, independent resource inside the IRS.