IRS Notice · Letter 566 · Audit by Mail · Read the Suffix

Letter 566: the suffix tells you how much time you have

A Letter 566 is how an audit by mail begins. There are several versions of it, they do different things, and one of them is already a 30-day letter — so the first thing to establish is not what the IRS wants, but which letter you are holding.

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Being selected is not an accusation, and the IRS says so itself: if it selects your return for audit, "it doesn't automatically mean something is wrong." The Taxpayer Advocate Service lists two outcomes for a completed examination, and accepting the return as filed is one of them.

What does need attention is the small letters after the number. A 566-S asks for documents. A 566-B arrives with the examination report already inside it, which means a window is already running.

(800) 236-3741 — answered 24 hours a day, seven days a week. After hours our AI receptionist answers the common questions, takes the letter number and the printed date, and books the first available thirty minutes. Thirty minutes, free, no obligation and no conditions — and a CPA works the case, not a salesperson.

Sixty seconds, tonight: read the suffix. 566-S, 566-E, 566-B or 566-J — the letters after the number. It decides whether you are being asked for documents or already sitting on a 30-day Appeals window, and it is the cheapest thing you will do in this whole process.

Key takeaways

•A Letter 566 is an initial contact letter — the IRS telling you a return has been selected for examination and asking for documentation.
•The suffix changes the letter. 566-S is generally used for a specific item; 566-E for wages, withholding and refundable credits; 566-B and 566-J arrive with the examination report enclosed.
•The combination letters give 30 or 45 days from the date of the letter, and the Taxpayer Advocate Service labels both of them "45 Day Combo."
•If you do not respond, the items in question are disallowed and a report follows showing the proposed changes.
•You can ask for an informal conference with the examiner's manager — but to keep your Appeals rights you must request the Appeals conference before the response date on the letter.

What a Letter 566 is

A Letter 566 is an initial contact letter opening a correspondence examination — an audit conducted entirely by mail. The Taxpayer Advocate Service describes the category:

"An Initial Contact Letter is your notification that your tax return has been selected for an audit (also called an examination). Included in the letter is a listing of the specific items reported on your tax return or that you failed to include on your return that are being questioned by the IRS, with a request that you provide documentation to support the identified items." — Taxpayer Advocate Service, "Letter Notifying Taxpayer of Audit with Request for Additional Information," read 6 September 2026

A note on sources, because it explains something about how hard this letter is to research. The IRS does not publish an "Understanding your Letter 566" page. It publishes one for CP2000, CP2501, CP3219A, CP22A, Letter 2030, Letter 2531 and Letter 3219B — we checked all of them — and none for Letter 566, Letter 525, Letter 531, Letter 692, Letter 915 or Letter 3219. What exists instead is the Taxpayer Advocate Service's notice pages, the Internal Revenue Manual, and Publication 3498-A. This page is written from those, and says so, because the obvious source does not exist.

Which letter you have

The suffix is the fact that changes what happens next, and it is on the letter.

Letter	What it is generally used for	What is enclosed
566-S	"the audit of a specific item"	A request for documentation
566-E	"the audit of wages, withholding, and refundable credits"	A request for documentation
566-B	Initial contact combined with the 30-day letter	The examination report, Form 4549
566-J	The same combination, by secure messaging, for international and Puerto Rico addresses	The examination report
2202B	A customized initial contact letter used for the same purpose as a 566-S	A request for documentation

Source: Taxpayer Advocate Service, "Letter Notifying Taxpayer of Audit with Request for Additional Information" and "Initial Contact Combined With 30-Day Letter and Report"; IRM 4.19.13.8 (04-06-2022). Read 6 September 2026.

Why this matters more than it looks. A letter asking for documents and a letter containing the IRS's proposed changes are different situations. The second one has already told you what the IRS thinks the answer is, and the window attached to it is also the window for requesting an Appeals conference. A reader who treats a 566-B as "they are just asking for paperwork" can spend the whole period gathering receipts and let the Appeals request date pass.

Your clock

It is the date printed on your letter, and the general periods differ by which letter you hold.

For the combination letters, the Taxpayer Advocate Service says:

"These letters give you 30 or 45 days (from the date of the letter), to provide the requested information or request a conference with the IRS Independent Office of Appeals if you disagree with the proposed changes to your tax return." — TAS, "Initial Contact Combined With 30-Day Letter and Report," last updated 12 May 2026

We are not going to reduce that to a single number. The same TAS page heads both 566-B and 566-J as "ICL 45 Day Combo" and then describes both as giving 30 or 45 days. Your letter carries the date; nothing on this page does.

If you need more time, the route is a phone call before the due date. Publication 3498-A: "If you are unable to meet the deadline, please call the number on the letter to discuss your situation and/or request additional time." TAS says the same. It is a request, not an entitlement, and it is markedly easier to make before the date than after it.

[If the date on your letter is inside two weeks, that changes the order of everything below. (800) 236-3741, day or night.]

Can they take my wages or my bank account over this?

No, and on most versions of this letter nothing has even been proposed yet. A 566-S or 566-E asks for documents; a proposed figure arrives later, as a Letter 525.

Where a report is already enclosed, the protection is still statutory. Section 6213(a) bars assessment of the proposed deficiency, and any levy or collection suit for it, until a Notice of Deficiency has been mailed and its 90 days — 150 if it is addressed to you outside the United States — have run, and until any Tax Court case is finished.

Three limits travel with that. The statute's own exceptions at sections 6851, 6852 and 6861 — termination and jeopardy assessments. A math or clerical error assessment, outside the bar under 6213(b)(1). And 6213(d): signing the agreement form enclosed with a report waives the restrictions yourself. None of it reaches a balance already assessed for a different year.

What triggered it

A return was selected for review and the IRS wants substantiation for specific items. Selection routes include computerized screening, statistical sampling, and document matching — and the Taxpayer Advocate Service's own description of what follows is worth reading twice:

"Once the IRS completes the examination, it will either accept your return as filed or propose changes to your return."

Accepting the return as filed is one of the two listed outcomes. That is not a consolation prize written to be kind; it is the IRS describing its own process.

What is being questioned is on the letter, and it is usually narrow: a deduction, a credit, a filing status, a business expense category, or the eligibility for a refundable credit. The scope of the letter is the scope of the audit until something in your answer widens it.

What happens if you do nothing

The items in question are disallowed and the IRS proposes the resulting tax. TAS:

"If you don't respond by the due date, the items in question will be disallowed and an examination report will be sent showing the proposed tax changes."

That report arrives as a Letter 525, the General 30-Day Letter — the one that opens the Appeals window. What a 30-day letter is, and what the 30 days is actually for (the CP2000 page covers the proposal-and-response structure in detail).

And if that one passes too: the Internal Revenue Manual for correspondence examinations sets out the next step without ambiguity. Where a Letter 525 was issued with a proposed report and no response was received, the instruction is to "issue 90 Day, Notice of Deficiency, Letter 3219." At that point the dispute leaves the IRS and becomes a court deadline. The Notice of Deficiency — the 90-day letter and the Tax Court window.

So the cost of silence at this stage is not the tax. It is that each step you skip removes a cheaper way to answer. Answering a Letter 566 costs an envelope. Answering a Letter 3219 costs a filing.

What to do in the next 30 days

1. Today: read the letter for two things only — the suffix, and the list of items. Everything else can wait an hour. Those two facts determine whether you are in a document request or already in a 30-day letter, and how wide the examination is.

2. Answer only what was asked. The IRS's guidance and the Taxpayer Advocate Service's both stress it: send copies, never originals, and put your name and taxpayer identification number on every page so the documents reach your file. Sending unrequested material is the most common way a narrow examination becomes a wide one.

3. Organize by item, not by date. The examiner is checking a list. Documents grouped to match that list get read as answers; a box of receipts gets read as an absence of answers.

4. If you cannot meet the date, call before it — not after.

5. Know the two conferences and the order they come in. You can ask for an informal conference with the examiner's manager, which costs nothing. And separately: "To preserve your right to a conference with the IRS Independent Office of Appeals, request an Appeals conference prior to the response date in the letter." That sentence is published by the Taxpayer Advocate Service for the combination letters — 566-B and 566-J — and not for the document-request letters, which is another reason the suffix matters. Nothing published says the manager conference moves the Appeals date, so protect that date whatever else you do.

The part that is genuinely hard is not gathering documents. It is knowing what counts as substantiation for the specific item the IRS named — which varies by item, and where the answer is often that a bank statement is not enough on its own. That is the thing an examiner is trained to assess and most taxpayers have never had to think about.

The Audit Response & Records Checklist

What the IRS asks for, item by item, and what "substantiation" actually means for the categories that come up most in a mail audit. It is the order we work in when a 566 arrives with a list on it. First name and email address, because substantiation rules change and a checklist nobody can correct is worse than none.

[ Get the checklist → ]

If the audit changes your numbers, Kentucky wants to know

If a federal examination changes your numbers, Kentucky has its own reporting duty and its own clock. Under KRS 141.211(2), a taxpayer files a federal adjustments report with the Department of Revenue and pays any additional state tax "no later than one hundred eighty (180) days after the final determination date."

Where the examination ends in an agreement signed by the IRS and the taxpayer, the statute makes the final determination date the date the last party signed. So for most people whose audit ends in a signed report, the Kentucky clock starts on their own signature — which is exactly the moment nobody is thinking about Frankfort.

Kentucky has one year from the filing of a timely report to assess. Where the report is late, never filed, or omits adjustments or understates the tax, that becomes six years — measured from the final determination date rather than from anything you do.

Source: KRS 141.211(1)(i) and (2), read 6 September 2026.

How Kentucky's process differs from the IRS's, and where the two interact

Katherine M. Johnson, CPA, CTRS

Katherine M. Johnson is a licensed CPA with over 30 years of experience and a Certified Tax Resolution Specialist (CTRS). She personally handles every case — representing individuals and businesses before the IRS and state revenue departments nationwide.

Read full bio

What we see

A Letter 566 tends to reach our office in Georgetown after a first reply has already gone in, so what we are handed is not really the letter — it is the question of whether it was answered well. One pattern is worth naming because it is well-intentioned: the taxpayer answered generously, sending everything that seemed relevant in one envelope, including years the letter never mentioned. That reads as cooperation, and it hands an examiner material about a year that was not being examined. The other is a 566-B treated as a request for documents, with the enclosed examination report unread and a response date running underneath it. Neither is carelessness — both are what a reasonable person does with a letter nobody has explained to them — which is why the first thing we read is the suffix and the second is whatever has already been sent.

Katherine — you are welcome to replace this with the mail audits that actually land here.

The IRS gives unlimited rights of representation to CPAs, enrolled agents and attorneys. Katherine is a CPA, and holds the Certified Tax Resolution Specialist designation alongside it. With a Power of Attorney on file, correspondence and calls run through the practice rather than through you — which for a mail audit is most of what representation is.

Where this sits in the sequence

Notice	What it is
566-S / 566-E / 566-B / 566-J▶ You are here	The initial contact letter. A return has been selected for a correspondence examination — an audit by mail.
Letter 525	The General 30-Day Letter — if the IRS proposes changes and no report was already enclosed. Opens the Appeals window.
Letter 3219	The Notice of Deficiency — 90 days to petition the Tax Court. The dispute leaves the IRS and becomes a court deadline.
CP2000	Often confused with this one — a document-matching proposal, not a mail audit.

What we do at this stage: IRS audit representation →CP2000 — the document-matching proposal →All notices: the IRS notice index →

Frequently asked

Am I being audited?

Yes — by mail. A correspondence examination is a real audit conducted through the post rather than in person, and it is the most common kind.

Does being selected mean the IRS thinks I did something wrong?

No. The Taxpayer Advocate Service puts it plainly: selection "doesn't automatically mean something is wrong," and one of the two listed outcomes is that the IRS accepts the return as filed.

How much time do I have?

The date on your letter. The combination letters are described as giving 30 or 45 days from the date of the letter; the document-request letters carry their own date. There is no single number that is right for every 566.

Can I ask for more time?

You can ask, by calling the number on the letter before the due date. It is a request rather than a right.

Should I send everything I have?

No. Send what was asked for, in copies, organized to match the list. Unrequested material is how a one-item examination becomes a three-item one.

If you'd rather not work it out alone

We handle IRS examinations for individuals and small businesses from our office in Georgetown, Kentucky.

The first useful thing is the suffix, and it takes about a minute. After that: what the named items actually require as substantiation, whether a 30-day window is already running, and whether anything in a reply you are planning risks widening the examination beyond the list the IRS wrote.

We do not know which suffix is on your letter, and it changes the advice completely. A 566-S with clean records and a single named item is a job a careful person does well alone: copies, organized to the list, sent by the date, proof of posting kept.

The versions worth thirty minutes:

the combination letters, 566-B and 566-J, where a report is already enclosed and a window is already running;
any letter naming a Schedule C, a rental or a refundable credit, where substantiation rules are specific and unforgiving;
any letter you have already answered once;
any letter whose printed date is inside two weeks and you cannot yet tell which of these you have.

The first consultation is free. It is thirty minutes. There is no obligation and no conditions attached to it.

And the thing worth knowing before you spend it: every case in this office is reviewed and worked by Katherine personally. Not handed to a processing department. Not managed by someone relaying messages from a licensed person you never meet. That is the difference between this and the firm advertising on the radio, and it is the one that shows up in month three rather than on the first call.

Bring the letter, and read out the number and the suffix — that is where the thirty minutes starts.

(800) 236-3741 — answered 24 hours a day, seven days a week. After hours you reach our AI receptionist rather than voicemail: it answers the common questions, takes the letter number, and books the first available thirty minutes.

This article is general information, not tax advice for your situation. Every account is different, and the options described here are not available to everyone. Next Level Tax Resolution is not affiliated with the Internal Revenue Service or any government agency.

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The NLTR Office ·

Reviewed by Katherine M. Johnson, CPA, CTRS