Types of IRS Audits

The three types of IRS audits

The IRS says it conducts audits “either by mail or through an in-person interview to review your records.” In-person audits come in two kinds: an office audit at an IRS office, and a field audit at “the taxpayer’s home, place of business, or accountant’s/representative’s office.” So there are three types in practice: correspondence (mail), office and field.

Being selected does not mean the IRS thinks you did something wrong. Publication 3498 says an inquiry or examination “does not suggest there’s a problem” and that the IRS may close the case with no change, or even issue a refund. Every audit starts the same way: the IRS notifies you by mail, and it says it “won’t initiate an audit by telephone.”

• Correspondence auditHandled entirely by mail, fax or upload
• Office auditAn interview at a local IRS office
• Field auditA revenue agent visits where your records are kept

Correspondence (mail) audits

Publication 3498 says the IRS “conducts some examinations entirely by mail.” You get a letter that asks for more information about specific items on your return, such as income, expenses, deductions or credits. The usual first letter is one of the Letter 566 series (for example 566-S or 566-E). The Taxpayer Advocate Service says these letters list the items being questioned and ask you to document them.

How a mail audit usually runs, per Publication 3498-A:

• You send copies, not originals, by the due date, using one of the reply options printed on the letter (mail, fax, or the IRS Document Upload Tool when the letter gives you that option). Put your name and taxpayer ID on each faxed page.
• You can ask for more time by calling the number on the letter before the deadline.
• The IRS confirms receipt. It says it will send a letter within 30 days acknowledging documents you mailed or faxed.
• You can ask for a face-to-face meeting, but the IRS says most cases are resolved by phone or correspondence, and the request must be in writing and explain why it is needed.

If you do not reply by the due date, the IRS “will disallow the items identified” and send an examination report with the proposed changes. Some letters in the series (566-B and 566-J) already enclose that report, Form 4549, and give you 30 or 45 days. Our audit letters guide explains each letter number.

Office audits

An office audit is an interview at an IRS office. The IRS manual (IRM 4.10.2, revised August 28, 2025) says it is “generally” held “in the IRS office closest to the taxpayer’s residence,” with the taxpayer’s home or business used only in extenuating circumstances. Office audits are run by tax compliance officers.

The first letter is usually Letter 3572, which asks you to call and schedule an appointment, or Letter 2202, which sets a firm date and time. Office examiners send Form 4564, an Information Document Request (IDR), with the first letter. It lists the records to bring and the date they are due. Under the same manual section, you get a minimum of 10 business days to find a representative if you want one, and if you ask to consult a representative during an interview, Publication 3498 says the IRS will suspend and reschedule it (unless you are there because of a summons).

At the end, office examiners generally send the report with Letter 915, a 30-day letter (IRM 4.10.8).

Field audits

A field audit is done by a revenue agent. IRM 4.10.2 says it is “generally” conducted “at the location where the original books, records, and source documents are maintained,” which “is usually the taxpayer’s principal place of business.” It can also take place at your home or at your representative’s office. If the time or place is not convenient, Publication 3498 says “the examiner will try to work out something more suitable.”

The first letter is Letter 2205 or Letter 2205-A; the 2205-A lists the issues the agent plans to examine. Form 4564 usually follows with the appointment confirmation letter. The IRS manual says “the scope of the examination is determined by the examiner,” so a field audit can widen as it goes. Requests often cover business books, bank statements and the source documents behind them. If you are self-employed, see what examiners check in small business audits.

Unagreed field cases end with Letter 950, the 30-day letter for field examinations (IRM 4.10.8). Field audits are where representation most often pays for itself, because the agent meets you in person and the scope can change.

How to tell which audit you have

The letter number tells you the type. Look for it on the letter, then use this table. You can also see audit status, letter dates and response due dates in your IRS Online Account under “Records and Status,” according to the IRS audits page.

Whatever the type, the end of an audit is the same: “no change,” “agreed” or a disagreement, per the IRS audits page. A disagreement leads to a 30-day letter with appeal rights, then a notice of deficiency.

How the IRS picks returns for audit

Publication 3498 (Rev. 5-2025) lists three ways a return can be selected:

• Random selection and computer screening. Sometimes the IRS selects returns “based solely on a statistical formula,” comparing your return against “norms” for similar returns. Publication 556 explains that a program called the Discriminant Inventory Function System (DIF) scores processed returns; a high score means an exam is more likely to change the tax.
• Related examinations. Your return may be pulled when it involves issues or transactions with other taxpayers, “such as business partners or investors,” whose returns were selected.
• Third-party documentation. Information from third parties, such as Forms 1099 and W-2, that doesn’t match your return.

On how far back an audit reaches, the IRS says it “can include returns filed within the last three years” and “usually” doesn’t go back “more than the last six years.” Longer periods apply in some cases; see how far back the IRS can go. For the patterns that tend to draw attention, read IRS audit red flags.

What is NOT an audit: CP2000, CP2501 and math-error notices

Several common IRS letters propose changes to your return without opening an audit. They still matter, because ignoring them can lead to a bill.

• CP2000. The Taxpayer Advocate Service says “Notice CP 2000 is not an IRS audit or a bill.” It comes from an automated comparison of your return with income and payment information from employers, banks and others. IRS Tax Topic 652 says to respond within 30 days of the notice date, or 60 days if you live outside the United States; if the IRS doesn’t hear from you, it sends a statutory notice of deficiency (usually a CP3219A). See our CP2000 guide.
• CP2501. An earlier-stage mismatch letter. The IRS says it “isn’t a bill, but you must respond” by the date on the notice. See CP2501 explained.
• CP11 and CP12 (math errors). The IRS “corrected one or more mistakes” on your return. Under IRC 6213(b), a math or clerical error notice is not a notice of deficiency, and you have 60 days to ask the IRS to reverse the change. The IRS pages for CP11 and CP12 warn that if you don’t contact it by the date on the notice, you lose formal rights to have the change reversed.

Handling it yourself, free help, and when to get a representative

Many mail audits are paperwork: one or two items and a clear list of documents. You can answer those yourself by the due date. Publication 3498 also lets you have someone represent you, usually an attorney, CPA or enrolled agent, by filing Form 2848. In an in-person audit, the representative can attend “with or without you being present.”

• Low Income Taxpayer Clinics represent eligible taxpayers in audits and appeals, for free or a small fee (find a clinic).
• Taxpayer Advocate Service helps for free when an IRS problem causes financial difficulty or normal channels fail: 877-777-4778 (IRS.gov, 2026).

Help is worth considering for a field audit, missing records, several years, or business income. Our audit representation guide covers when a representative is worth it. Not sure which audit you have? Get a free review or call 1-877-800-8180. Global Gate Tax Relief quotes a flat fee upfront if it takes the case and does not promise outcomes.

Frequently asked questions

Keep reading in the IRS Audit Guide

• IRS audit letters explainedLetter 566, 525, 950, 3219 and Form 4549 decoded.
• First steps after an audit letterA calm checklist for the first 10 days.
• Audits for self-employed taxpayersWhat examiners check on Schedule C.
• The 30-day letterAgree, disagree or request Appeals.
• CP2000 noticeThe underreported income notice that is not an audit.