Letter 566 is the IRS's way of telling you that your tax return has been selected for an audit by mail, called a correspondence examination. It lists the specific items the IRS is questioning, such as a deduction, a credit or a type of income, and asks you to send documents that support them. Most audits by mail cover only a few items and are handled entirely in writing. Selection doesn't automatically mean anything is wrong. What matters most is a complete, organized reply by the due date.
Why you got a Letter 566
The IRS accepts most returns as filed but selects some to check that income, expenses and credits are reported accurately. According to the IRS, it selects returns using methods such as random sampling, computer screening, and comparison with forms like W-2s and 1099s.
Letter 566 comes in several versions, each used for a slightly different situation. The Taxpayer Advocate Service lists them, including:
- Letter 566-S, generally used to audit a specific item.
- Letter 566-E, typically used to audit wages, withholding and refundable credits.
- Letter 566-T, which invites you to use secure online messaging with the examiner.
- Letter 566-B and 566-J, "combo" letters that include a proposed examination report (Form 4549) and give you 30 or 45 days to send information or ask for an Appeals conference.
What the Letter 566 says
Look for:
- The tax year under audit.
- The items being examined, often with a separate page or form for each that explains what proof the IRS needs.
- The due date to send your documents.
- How to respond: mailing address, fax number, and in many cases an upload option or secure messaging.
- Contact information: a phone number to reach an examiner.
- Questionnaires, if any, to complete and return.
- Publication 3498-A, which explains the mail audit process and your rights.
If you received a 566-B or 566-J, it also includes a report showing the tax change the IRS will make if you don't send support.
What to do
- Mark the due date. If you need more time, call the number on the letter before that date.
- List what's being asked. Make a checklist from the letter, item by item.
- Gather proof for each item. Receipts, bank and card statements, canceled checks, mileage logs, school or medical records, letters from third parties. Where you lack a receipt, write a short explanation of how you figured the amount.
- Organize it. Group documents by item, label them, and add a short cover letter that lists what's enclosed. Fill out any questionnaires.
- Send copies, never originals, using an option the letter lists. If you fax or upload, put your name and Social Security number (or ITIN) on every page.
- Keep a full copy of what you sent and proof of when you sent it.
If you need more time
Call the number on the letter before the due date. Under the IRS's internal procedures for correspondence audits, a first request for more time to send documents is generally granted for an extra 30 days, added to the original due date. Further requests are up to the examiner. Extensions may be refused if fewer than 180 days remain on the time limit for the IRS to assess tax, unless you agree to extend that limit.
If you have a large volume of records
Publication 3498-A says to call the number on the letter if you can't fax or mail everything because of the volume. You may be asked for an itemized list instead.
If you can't find some documents
Send what you have and explain the rest. Banks, employers, schools and doctors can often supply copies of records. Reconstructed records with a clear explanation are better than nothing.
A Low Income Taxpayer Clinic may represent you for free if you qualify, and a CPA, enrolled agent or tax attorney can handle the audit for you with a Form 2848 power of attorney. Self-employed? Our self-employed hub explains the records that support Schedule C. An optional audit response kit with checklists and cover letter templates exists on this site, but everything you need to respond is described here.
What happens next, and if you ignore it
After reviewing your documents, the IRS will either ask for more information, accept your return as filed (and send a letter saying so), or propose changes. The IRS says it will send a letter within 30 days acknowledging documents you mailed or faxed.
If it proposes changes, you will receive an examination report with a 30-day letter, usually Letter 525. If you don't respond to Letter 566 at all, the IRS will disallow the items in question and send that report. If you still don't respond or reach agreement, a statutory notice of deficiency follows, giving you 90 days to go to the U.S. Tax Court (see CP3219A for how that works). Our IRS audit guide walks through the full process.
Is this letter real?
The IRS starts audits by mail. Its examiners may later call to discuss your audit, but only after a letter. Check that the return address is the IRS, and confirm the letter by calling the IRS at a number listed on irs.gov rather than one from an unexpected email or text. Your IRS Online Account also shows your account history for the year. The IRS doesn't demand payment by gift card or wire transfer. See how to spot IRS scams.
Frequently asked questions
How long does an audit by mail take?
It varies. The IRS says audits where all requested documents or a signed agreement are received can close quickly, while others take several months. Responding on time with everything requested helps.
Can I talk to the examiner?
Yes. Call the number on the letter. If you need your specific examiner, you can ask for a callback. Face-to-face meetings are possible for complex cases, but the request must be in writing and explain why.
Should I still file my next tax return?
Yes. Keep filing all required returns on time while the audit is open, to avoid new penalties and interest.
What if I filed jointly and my spouse caused the problem?
You may qualify for innocent spouse relief by filing Form 8857. Publication 3498-A describes the types of relief.
Will the IRS contact other people about my audit?
Sometimes. The IRS says it may contact third parties, such as a bank or employer, to get or verify information, and you can ask for a list of those contacted.
Sources
- Taxpayer Advocate Service (TAS), "Letter Notifying Taxpayer of Audit with Request for Additional Information". taxpayeradvocate.irs.gov
- TAS, "Initial Contact Combined With 30-Day Letter and Report". taxpayeradvocate.irs.gov
- Internal Revenue Service (IRS), Publication 3498-A, "The Examination Process (Audits by Mail)" (Rev. 5-2021). irs.gov
- IRS, Internal Revenue Manual 4.19.13.11.7, Taxpayer Requests Additional Time to Respond. irs.gov
- IRS, "How to know it's really the IRS calling or knocking on your door". irs.gov
IRSV.com is an independent guide and is not affiliated with the IRS. This page is general information, not tax or legal advice. Rules change; confirm details on IRS.gov or with a tax professional. Found an error? Tell us.