IRS Examination Guide

IRS Audit: Types, Time Limits, Your Rights and the Appeals Process

By Ray Neu, Publisher | Last reviewed: October 25, 2026 | Reading time: 9 min

Short answer

An IRS audit is a review of a tax return to verify that income and tax were reported correctly. The IRS starts audits by mail, not by phone, and conducts them by mail, at an IRS office or in the field. Under 26 U.S.C. § 6501(a), it generally has 3 years after a return is filed to assess more tax.

The IRS says selection “does not always suggest there’s a problem,” and Publication 1 notes an examination may end with no change or even a refund. This guide covers how audits are run, how far back they reach, the rights the law gives during one, and how a disagreement moves to Appeals and the U.S. Tax Court.

Deadline to know: Under 26 U.S.C. § 6213(a), a notice of deficiency (the “90-day letter”) allows 90 days from mailing, or 150 days if addressed outside the United States, to petition the U.S. Tax Court. Neither the IRS nor the Court can extend it.

Received an IRS audit letter or a 30-day letter?
Free, confidential evaluation.

Start Your Free Evaluation

Or call (202) 968-1121

How the IRS notifies you of an audit

The IRS says it notifies selected taxpayers by mail and “won’t initiate an audit by telephone.” A revenue agent, who conducts field audits, contacts the taxpayer by mail first and may call afterward. The IRS also says a call, email or text is not from the IRS if it is unexpected, rushes or threatens you, asks for personal or financial information, or demands payment now. Agents carry a pocket commission and an HSPD-12 card, and taxpayers may ask to see both.

More time. For mail audits, the IRS can ordinarily grant a one-time automatic 30-day extension. For in-person audits, the request goes to the assigned auditor.
No reply. The IRS will complete the audit and send a report with its proposed changes.
A CP2000 is different. That notice comes from automated matching of a return against Forms W-2 and 1099, and the Internal Revenue Manual treats these contacts as “not considered an examination” (IRM 4.19.3.1.2).

The three types of IRS audit

The IRS conducts audits “either by mail or through an in-person interview.” Publication 3498-A covers audits by mail; Publication 3498 covers examinations generally.

Type	How it works
Correspondence (mail)	A letter asks about items such as income, expenses or itemized deductions. Send photocopies, not originals. With too many records to mail, a face-to-face audit can be requested.
Office audit	An in-person interview at an IRS office, scheduled by mail.
Field audit	At the taxpayer’s home, business, or accountant’s or representative’s office. A visit may require a tour of the business.

The IRS describes several ways returns are selected:

Random selection and computer screening. Comparing a return with “norms” for similar returns, built from audits of a random sample under the National Research Program.
Related examinations. Transactions with partners or investors whose returns were selected.
Third-party documentation. Forms 1099 and W-2 that do not match the return.
Outside sources. Publication 1 lists newspapers, public records and individuals, if the IRS finds the information reliable.

The IRS adds that a refund “is not necessarily a trigger for an audit.” If the same items were examined in either of the 2 previous years with no change, Publication 1 asks taxpayers to contact the IRS so it can consider ending the exam.

How far back an IRS audit can go

Section 6501(a) requires assessment within 3 years after a return is filed, and § 6501(b)(1) treats an early return as filed on its due date. After that, the IRS can no longer assess additional tax. The exceptions:

6 years under § 6501(e) when omitted gross income exceeds 25 percent of the gross income stated on the return.
No limit for a false or fraudulent return filed to evade tax, under § 6501(c)(1), or when no return was filed, under § 6501(c)(3).

In practice, the IRS says it generally audits returns filed within the last three years, may add years for a substantial error, and usually does not go back more than six.

Requests to extend the statute

Under § 6501(c)(4), the taxpayer and the IRS may agree in writing, before the period ends, to extend it, and the IRS must explain the right to refuse or to limit the extension to particular issues or a set period. Publication 1035 names Form 872 as the fixed-date consent used in most examinations; Form 872-A is open-ended. Signing is not required, but the IRS says the auditor will then “make a determination based upon the information provided,” and Appeals generally needs at least 365 days left on the statute to take a case.

How long to keep records

The IRS ties record retention to the same periods: 3 years in most cases; 6 years if unreported income is more than 25% of gross income shown; 7 years for a worthless securities or bad debt claim; indefinitely if no return or a fraudulent return was filed; and at least 4 years for employment tax records.

Your rights during an IRS audit

Section 7803(a)(3) lists ten taxpayer rights the IRS must honor, explained in Publication 1, including the rights to be informed, to challenge the IRS’s position and be heard, to appeal in an independent forum, to finality, to privacy and to retain representation. The IRS says finality includes knowing when an audit is finished. Section 7521 adds rules for interviews:

An explanation first. Under § 7521(b)(1), the IRS must explain the audit process and the taxpayer’s rights before or at the first in-person interview.
Stopping to consult. Under § 7521(b)(2), if a taxpayer clearly says during an interview that they wish to consult an attorney, CPA, enrolled agent or other authorized representative, the IRS must suspend it, even if questions were already answered. Interviews started by an administrative summons are the exception.
A representative. Authorization is made on Form 2848. Under § 7521(c), the IRS may not require the taxpayer to attend with the representative absent a summons.
Recording. On advance request, § 7521(a)(1) allows an audio recording of an in-person interview with the taxpayer’s own equipment.
Third-party contacts. The IRS may contact banks or employers to verify information, and Publication 1 gives a right to request a list of those contacted.

Facing an interview, a consent form or a 90-day letter?

A free evaluation is a chance to talk through the examination and appeal options the law provides with a tax attorney.

Start Your Free Evaluation Call (202) 968-1121

How an audit ends and how disagreements are resolved

The IRS says an audit ends one of three ways. No change: every item was substantiated. Agreed: the taxpayer accepts the proposed changes and signs the examination report; any balance then moves to payment (see our back taxes guide). Disagreed: the taxpayer understands but disputes the changes, and Publication 3498-A says not to sign the agreement page. A disagreement then follows these steps:

Manager or mediation. The taxpayer can request a conference with an IRS manager or Fast Track Settlement, a voluntary process in which an Appeals employee acts as a neutral party.
The 30-day letter. It explains the right to appeal, and the taxpayer generally has 30 days to accept or appeal. After a mail audit this is generally Letter 525; after a field audit, Letter 950.
Appeals. The IRS Independent Office of Appeals is separate from the examiner. Under Publication 5, if tax and penalties for each period total $25,000 or less, a small case request (a brief statement or Form 12203) is enough; above that, a formal written protest is required. Arguments must rest on tax law.
The 90-day letter. Without a settlement, the IRS issues a notice of deficiency, sent by certified or registered mail under § 6212. Under § 6213(a), it generally cannot assess or levy until the 90 or 150 days pass or a Tax Court decision is final. The underreporter program’s version is the CP3219A.
U.S. Tax Court. A petition, on paper or through the Court’s DAWSON system, starts the case. The fee is $60 as of October 2026 and may be waived for inability to pay. The disputed tax usually need not be paid first, though interest runs, and small tax case procedures cover disputes of $50,000 or less per year. With no petition, the IRS sends a bill.

Sources differ on one figure. Publication 3498-A counts interest toward the $25,000 small case limit; Publication 3498 (Rev. 5-2025) and Publication 5 count tax and penalties only.

When an attorney matters

Help is not required: Publication 3498-A says taxpayers may represent themselves. Before the examiner and Appeals, attorneys, CPAs and enrolled agents can all represent a taxpayer. Taxpayers in these situations often ask a tax attorney to review the facts:

A Tax Court case. The Court admits attorneys by application, while nonattorneys must pass its examination and a character and fitness review.
Confidentiality. Section 7525 extends attorney-style confidentiality to other federally authorized tax practitioners only in noncriminal tax matters, and not for written tax shelter promotion.
A possible fraud referral. Under IRM 25.1.2.2, when an examiner establishes affirmative acts of fraud, the exam is suspended and a referral to Criminal Investigation may follow. There, the § 7525 limit matters.
Years with no return. These have no assessment limit; see our guide to unfiled tax returns.

Related guides

Frequently Asked Questions

Does the IRS call to start an audit?

No. The IRS says it notifies taxpayers of an audit by mail and will not initiate one by telephone. A revenue agent writes first and may call afterward.

How far back can the IRS audit a tax return?

Generally 3 years after filing under 26 U.S.C. § 6501(a), or 6 years if omitted income exceeds 25 percent of the gross income reported. There is no limit for a fraudulent return or no return. The IRS says it usually does not go back more than six years.

How long does an IRS audit take?

The IRS says it depends on the type of audit, the complexity of the issues, the availability of requested information, scheduling, and whether the taxpayer agrees. Mail audits can close quickly once all requested documents arrive; others can take several months.

Is a CP2000 notice an audit?

No. A CP2000 comes from the IRS Automated Underreporter program, and the Internal Revenue Manual treats these contacts as not considered an examination. It is a proposed change, not a bill, and may still require a reply by the date listed.

Can I stop an audit interview to talk to a representative?

Yes, in most cases. Under 26 U.S.C. § 7521(b)(2), if a taxpayer clearly asks to consult an attorney, CPA, enrolled agent or other authorized representative, the IRS must suspend the interview, unless it was started by an administrative summons.

Questions about an IRS examination?

Start a free, confidential evaluation to talk with a tax attorney about the audit letter and the deadlines on it.

Start Your Free Evaluation Call (202) 968-1121

About the Author

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.

LinkedIn Profile →

Sources

IRS Circular 230 Disclosure: To ensure compliance with Treasury Department rules governing tax practice, any tax information contained on this website was not written and is not intended to be used, and cannot be used, for the purpose of avoiding any federal tax penalty. You should consult a licensed tax professional regarding your individual situation.

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.