Statute of Limitations on IRS Audits: 3, 6, or Forever?

The statute of limitations on IRS audits is three years from the date you filed your return in most cases, six years if you left more than 25% of your gross income off the return, and unlimited if the return was fraudulent or you never filed one at all. The deadline applies to assessment, meaning the IRS has to finish its work and formally assess any additional tax before the clock runs out, not just start looking.

The Three-Year Default

Three years is the standard window, measured from the date your return was filed.¹ If you filed early, the IRS treats the return as filed on the due date. A return submitted in February for a tax year with an April 15 deadline doesn’t start the three-year clock until April 15. File late without an extension, and the clock starts on the date the IRS actually receives the return.

This is an assessment deadline, not an audit-start deadline. The IRS doesn’t just need to begin reviewing your return within three years. It needs to finish and formally assess any additional tax before the three years run out. An examination that starts in year two but drags past the three-year mark without an assessment means the IRS loses its ability to collect on anything the examiner found. That pressure is why the agency sometimes asks you to sign an extension as the deadline approaches.

Six Years for Substantial Omissions

If you leave more than 25% of your reported gross income off your return, the IRS gets six years instead of three.¹ The comparison is between the omitted amount and the gross income you actually reported, not your total real income. If your return shows $100,000 in gross income but you failed to report an additional $30,000, the omission exceeds 25% and the longer window applies.

A separate trigger covers foreign financial assets. If you omit more than $5,000 of income tied to assets that should have been reported under the foreign asset disclosure rules, the six-year period applies regardless of whether the omission crosses the 25% threshold.¹ This catches cases where the dollar amount is modest but international reporting was skipped.

When There Is No Time Limit

Three situations remove the statute of limitations entirely and leave the IRS with an indefinite window.

Fraudulent returns. If you filed a false or fraudulent return with intent to evade tax, the IRS can assess additional tax at any time. The burden sits with the IRS, which must show by clear and convincing evidence that you intended to evade tax. A careless mistake is not fraud, even a large one.¹
No return filed. If you never filed a required return, the assessment period never starts. The IRS can come after you decades later. Filing the overdue return voluntarily does start the three-year clock, so there is a real incentive to file even when you’re years behind.²
Unreported gifts. If a taxable gift that should have been disclosed on a gift tax return was left off entirely, or was described without enough detail for the IRS to evaluate it, the IRS can challenge that gift at any time. Adequate disclosure starts the normal three-year period.³

Does Filing an Amended Return Restart the Clock?

Generally, no. Filing an amended return does not restart or extend the assessment deadline on your original return. The expiration stays anchored to when you filed, or should have filed, the original.⁴

One narrow exception matters. If the IRS receives your amended income tax return during the last 60 days before the assessment deadline expires, the IRS gets an additional 60 days from the date it received the amendment to assess any additional tax shown on that amendment. The extra 60 days applies only to income tax returns and only to changes reflected on the amendment itself. It does not reopen the entire original return for a fresh examination.⁴

Amending to correct an error or claim a missed deduction doesn’t hand the IRS a new three-year window to scrutinize everything. The clock keeps running on the original timeline.

When the Clock Pauses

Several events freeze the assessment period, effectively adding time to the IRS’s deadline.

Notice of Deficiency and Tax Court

When the IRS sends you a formal notice of deficiency, often called a 90-day letter, the assessment clock stops automatically. The IRS is prohibited from assessing the tax while you have time to petition the Tax Court: 90 days for domestic taxpayers, 150 days if the notice is addressed outside the United States.⁵

If you file a petition, the freeze continues until the Tax Court’s decision becomes final, plus an additional 60 days.⁶ A case that takes two years effectively adds those two years to the IRS’s assessment window. This is built into the law.

Voluntary Extensions by Agreement

If an audit is still underway as the three-year deadline approaches, the IRS will usually ask you to sign a consent form extending the assessment period. Two main forms are used, and they work very differently.

Form 872 (fixed-date consent). Sets a specific future expiration date. Once that date passes, the extension ends automatically and the IRS can no longer assess additional tax for that year.⁷
Form 872-A (open-ended consent). No expiration date. The extension stays in effect until either you or the IRS files a Form 872-T to terminate it, at which point the IRS has 90 days to make any assessment.⁷

You are not legally required to sign either form. Refusing can push the IRS to issue a notice of deficiency immediately based on whatever information it has, which often means a larger proposed adjustment than you would face if the examiner had time to review your documentation. Signing an extension buys time for both sides and preserves your ability to negotiate before the IRS locks in a number.⁸

If you do agree to extend, ask for a fixed-date Form 872 rather than the open-ended 872-A whenever possible. The fixed date gives you a hard deadline and prevents the audit from dragging on indefinitely. Both parties can also agree to restrict the consent to specific tax issues rather than the entire return, which limits what the IRS can revisit during the extension.⁷

Collection Is a Separate Ten-Year Clock

The audit period and the collection period are two different clocks. Once the IRS formally assesses your tax, whether from your original return, an amended return, or an audit adjustment, a separate ten-year collection period begins. This is called the Collection Statute Expiration Date, or CSED.⁹ After ten years, the IRS must generally stop collection efforts and any remaining balance expires.¹⁰

That ten-year collection window can itself be paused by things like bankruptcy filings, pending installment agreements, offers in compromise, collection due process hearings, and innocent spouse claims. Each pause pushes the CSED further out.¹¹ You can find your specific CSED in the Transactions section of your IRS account transcript.⁹

How Long to Keep Your Records

Your record retention should match the longest statute of limitations that could apply. The IRS guidelines track the assessment periods above:¹²

Three years minimum. Measured from the filing date or due date, whichever is later. This covers the standard assessment period.
Six years. If you have foreign financial assets or any concern about potential underreporting, keep records for six years.
Seven years. If you claimed a deduction for bad debts or worthless securities, keep records that long to support any related refund claim.
Indefinitely. If you didn’t file a return or filed a fraudulent one, there is no expiration on the IRS’s authority. Keep everything.

Property records deserve special attention. Hold onto purchase records, improvement receipts, and depreciation schedules until the statute of limitations expires for the year you sell or dispose of the property, not the year you bought it. If you purchased a rental property in 2015 and sell it in 2026, keep those 2015 purchase records until at least 2029. Employment tax records carry a four-year minimum, measured from the date the tax is due or paid, whichever is later.¹²

1
Office of the Law Revision Counsel. 26 USC 6501 – Limitations on Assessment and Collection
2
Internal Revenue Service. Time IRS Can Assess Tax
3
Office of the Law Revision Counsel. 26 US Code 6501 – Limitations on Assessment and Collection
4
Internal Revenue Service. IRM 25.6.1 Statute of Limitations Processes and Procedures
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Office of the Law Revision Counsel. 26 US Code 6213 – Restrictions Applicable to Deficiencies; Petition to Tax Court
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Office of the Law Revision Counsel. 26 USC 6503 – Suspension of Running of Period of Limitation
7
Internal Revenue Service. IRM 25.6.22 Extension of Assessment Statute of Limitations by Consent
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Internal Revenue Service. Publication 1035 – Extending the Tax Assessment Period
9
Internal Revenue Service. Time IRS Can Collect Tax
10
GovInfo. 26 USC 6502 – Collection After Assessment
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Taxpayer Advocate Service. Understanding Your Collection Statute Expiration Date
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Internal Revenue Service. Topic No. 305, Recordkeeping