IRS Letter 566: What the Audit-by-Mail Letter Asks For
IRS Letter 566 is the initial contact letter for a correspondence examination, the IRS term for an audit by mail. It lists the return items under review and asks for copies of supporting records by the due date printed on the letter. With no reply, the questioned items are disallowed and a report of proposed changes follows.
The IRS does not keep an “Understanding your Letter 566” page; that address returned an error when checked for this review. This guide draws instead on the Taxpayer Advocate Service, Publication 3498-A, the IRS audits page, an IRS video script, and IRM 4.19.13, the manual chapter correspondence examiners follow.
Deadline to know: The reply is due by the date printed on the letter. For the combination versions, Letters 566-B and 566-J, the Taxpayer Advocate Service describes “30 or 45 days (from the date of the letter).” The IRS audits page says the IRS can “ordinarily” grant a one-time automatic 30-day extension when asked in writing.
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What Letter 566 is
The Taxpayer Advocate Service (TAS) calls this series of initial contact letters “your notification that your tax return has been selected for an audit.” Each one names the specific items reported on the return, or missing from it, that the IRS is questioning, and requests documents backing them up.
Being picked is not a finding. TAS says selection “doesn’t automatically mean something is wrong,” and Publication 1 states that an examination “does not suggest that you are dishonest” and may close with no change or with a refund. Real audits begin on paper: the IRS audits page says “We won’t initiate an audit by telephone.”
Where it sits in the process
Letter 566 opens a mail audit. When the examiner is ready to propose changes, IRM 4.19.13 has the campus send Letter 525, the General 30 Day Letter, with the proposed report and appeal options; that stage is covered in the Letter 525 guide. Audits held in person at an IRS office or at a home or business (office and field audits) run on a different track, described in the IRS audit overview.
Which version of Letter 566 you have
An IRS video on correspondence exams says the letter number sits in the bottom right hand corner, giving “LETTER 566-S” as its example. TAS lists many versions in the series; these are the ones official sources describe:
| Version | What the sources say |
|---|---|
| 566-S | Used “for the audit of a specific item” (TAS); the letter IRM 4.19.13.8 names when the examiner is requesting information only |
| 566-E | Typically for “wages, withholding, and refundable credits” (TAS) |
| 566-T | Secure Messaging version sent in place of 566-S to taxpayers invited into the IRS digital program (IRM 4.19.13.33.1) |
| 566-B | “ICL 45 Day Combo”: audit notice with an enclosed Form 4549 showing the potential result (TAS) |
| 566-J | Secure Messaging version of the 45 Day Combo, sent in place of 566-B (TAS; IRM 4.19.13.33.1) |
The combination letters stand apart because a proposed outcome is already enclosed. TAS says they allow time either to supply the requested information or to ask for a conference with the IRS Independent Office of Appeals, and that an Appeals request belongs before the response date shown.
What to send and how to send it
Per the IRS audits page, a mail audit letter asks about items “such as income, expenses, and itemized deductions.” Publication 3498-A asks for photocopies attached to the letter and sent to the address or fax number it gives. Across the official sources, the packaging points line up:
- Copies only. TAS, Publication 3498-A and the IRS video all say not to send originals.
- One organized package. The video asks for every requested document “AT ONE TIME,” grouped by issue, each page numbered, with a summary sheet listing the documents and where to find them.
- Identifiers. The summary sheet carries name, Social Security number, the tax year under audit, a phone number and the letter number. TAS asks for name and taxpayer identification number on every faxed or uploaded page.
- Readable, dated records. Records should be for the year requested, show the issuing institution or account owner, and show dates, including the date paid. Attached questionnaires go back completed.
- Gaps. Where an amount cannot be verified, Publication 3498-A asks for an explanation of the issue and how the amount was determined.
Delivery options
The letter itself lists the channels that apply. Publication 3498-A names mail and fax. IRM 4.19.13.33 adds the Document Upload Tool and, for invited taxpayers only, a Secure Messaging portal where documents “can be uploaded.” For records too bulky to fax or mail, Publication 3498-A says to call the number on the letter. The IRS audits page notes that a face-to-face audit can be requested, and Publication 3498-A says that request has to be in writing and explain why it is necessary.
Proof it arrived
The IRS audits page recommends delivery confirmation from whatever carrier is used. Publication 3498-A says the IRS will send a letter within 30 days acknowledging documents received by mail or fax. When the letter shows the contact number 866-897-0177 or 866-897-0161, audit status, letter dates and the next due date appear in the individual online account under “Records and Status.”
Response time and extensions
Publication 3498-A puts it plainly: reply “by the deadline given in the letter.” None of the official sources reviewed gives a fixed number of days for Letter 566-S or 566-E, so the printed date is the one that counts.
Internally, IRM 4.19.13.2.4 sets suspense periods, the time staff wait from the letter date before mailing the next letter: 30 days for EITC, TS non-EITC and single-issue premium tax credit initial contact letters without a report, 45 days for SB/SE non-EITC ones, and 60 days for the combination letter that includes a report. Those figures are written for IRS employees and do not move the date on the letter.
Asking for more time
- IRS audits page. Fax a written request to the number on the letter, or mail it if faxing is not possible. The IRS says it “can ordinarily grant” a one-time automatic 30-day extension and will get in touch if it cannot.
- TAS and Publication 3498-A. Both point to the phone number on the letter, used before the due date.
- IRM 4.19.13.11.7. A first request adds 30 days to the original due date shown on Letter 566-S or 566-T. No extension is granted when 180 days or less remain on the statute of limitations, unless the taxpayer agrees to extend the statute and the facts warrant it. SB/SE campuses answer with Letter 686-B within three business days.
What happens next, or after silence
Once a reply is reviewed, TAS says the examiner will request more information, accept the original return as filed, or propose changes. Publication 3498-A says acceptance comes in a letter worth keeping with tax records, while a rejected submission brings a letter laying out the proposed changes.
With no reply, TAS says the questioned items “will be disallowed” and a report of proposed changes will follow. Publication 3498-A adds that a refund may be delayed or reduced and that interest keeps accruing on any balance. Under IRM 4.19.13.13, once the waiting period lapses, the campus mails Letter 525 together with the proposed examination report, Form 886-A explaining each disallowed item, Publication 3498-A, and Form 14817, a reply cover sheet.
If that 30-day letter also goes unanswered, the same IRM table calls for Letter 3219, the 90-day Notice of Deficiency. How a statutory notice of deficiency works, including the Tax Court petition window, is explained in the CP3219A 90-day letter guide.
Questions about a Letter 566 request?
An attorney can review what the letter asks for and explain how the correspondence exam process works.
Rights during a mail audit
- Interview option. Publication 1 says a mail exam can be answered by mail or by requesting a personal interview with an examiner.
- Repeat audits. If the same items were examined in either of the 2 previous years and no change was proposed, Publication 1 asks taxpayers to contact the IRS so it can consider ending the exam.
- Third parties. The IRS sometimes asks other people to verify information; Publication 3498-A gives a right to request a list of those contacted.
- Recordkeeping. The IRS audits page says the law requires keeping the records used to prepare a return for at least three years from the filing date.
- Length. Publication 3498-A says some audits “can take several months.”
When an attorney matters
Nothing in the sources requires a representative for a mail audit. Publication 3498-A says a taxpayer may act alone or, “with proper written authorization,” use someone allowed to practice before the IRS, “such as an attorney, certified public accountant, or enrolled agent.” Publication 1 lists the right to retain representation and to seek help from a Low Income Taxpayer Clinic. The sources show where the type of representative makes a difference:
- Authorization. Form 2848 authorizes a representative and lets that person receive confidential tax information. IRM 4.19.13 tells examiners to check for one on file, contact the representative in place of the taxpayer, and copy the representative on letters.
- Unenrolled preparers. Under the Form 2848 instructions, an unenrolled return preparer may represent only in the exam of a return the preparer prepared and signed, never before appeals officers, and cannot sign an extension of the assessment period.
- If the case reaches Appeals. Publication 3498-A allows only attorneys, CPAs and enrolled agents to represent there; an unenrolled preparer may take part only as a witness.
- Privilege. Section 7525 gives communications with non-attorney federally authorized practitioners attorney-style confidentiality only in noncriminal tax matters.
The attorney, CPA and enrolled agent comparison sets out the three roles side by side.
Related guides
Frequently Asked Questions
Does a Letter 566 mean the IRS found a mistake?
Not necessarily. TAS says selection “doesn’t automatically mean something is wrong,” and Publication 1 says an exam may close with no change or a refund. The letter asks for support on specific items; the examiner then accepts them, asks for more, or proposes changes.
How long is there to answer Letter 566?
Until the due date printed on the letter. For the combination Letters 566-B and 566-J, TAS describes 30 or 45 days from the letter date. The IRS audits page says a one-time automatic 30-day extension can ordinarily be granted on a written request.
Can the documents be sent electronically?
Sometimes. IRM 4.19.13.33 names the Document Upload Tool, fax or mail, plus a Secure Messaging portal for invited taxpayers who receive Letter 566-T or 566-J. The letter lists the channels that apply to that case.
What if a receipt or record is missing?
Publication 3498-A says that when an amount cannot be verified, the reply should explain the issue and how the amount was determined. The examiner then decides whether to accept the item or propose a change.
What happens if Letter 566 is ignored?
TAS says the questioned items will be disallowed and a report of proposed changes will be sent. IRM 4.19.13.13 names that next mailing as Letter 525, and an unanswered Letter 525 leads to Letter 3219, the 90-day Notice of Deficiency.
Talk through a Letter 566 before the due date
A free, confidential evaluation can help explain the mail audit steps and the representation options the rules allow.
Ray Neu
Ray Neu is the publisher of IRSAttorneys.net. A former law enforcement officer with a background in criminal justice and digital publishing, he oversees editorial direction, partnership standards, and compliance review for the site. He is not an attorney and does not provide legal advice; all tax law content is sourced and reviewed against the standards documented on the Editorial Team & Standards page.
Sources
- Taxpayer Advocate Service: Letter notifying taxpayer of audit with request for additional information
- Taxpayer Advocate Service: Initial contact combined with 30-day letter and report
- IRS Publication 3498-A, The Examination Process (Audits by Mail)
- IRS: IRS audits
- IRS: Organizing files for correspondence exams (video text script)
- IRM 4.19.13, General Case Development and Resolution
- IRS Publication 1, Your Rights as a Taxpayer
- IRS: Instructions for Form 2848
- 26 U.S.C. § 7525, Confidentiality privileges relating to taxpayer communications
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Results described on this website are not a guarantee, warranty, or prediction of the outcome of any tax matter. Every situation is different. Prior results do not guarantee a similar outcome. Article content reflects general information about federal tax procedure as of the last reviewed date and may not reflect subsequent changes in IRS policy, regulations, or case law.