Statute of Limitations on IRS Audits: 3, 6, 10, or Forever

The IRS generally has three years from the date you filed a return to audit it and assess more tax, and that is the statute of limitations on IRS audits for most taxpayers. The window stretches to six years if you left more than 25% of your gross income off the return, and it disappears entirely if the return was fraudulent or was never filed at all.¹

The Three-Year Default

Three years is the standard assessment period, measured from the date the return was filed. File early and the IRS treats the return as filed on the due date, so a February return for an April 15 deadline doesn’t start the clock until April 15. File late without an extension and the clock starts the day the IRS actually receives your return.¹

Read the deadline carefully. It’s an assessment deadline, not an audit-start deadline. The IRS doesn’t just need to open an examination within three years. It needs to finish the work and formally assess any additional tax before the window closes. An audit that begins in year two but drags past the three-year mark without an assessment leaves the IRS unable to collect on anything it found. That pressure is why examiners sometimes ask you to sign a consent extending the deadline, discussed below.

The Six-Year Window for Substantial Omissions

Leave more than 25% of your reported gross income off the return and the IRS gets six years instead of three. The comparison is between the omitted amount and the gross income you actually reported. If your return shows $100,000 in gross income but you failed to report another $30,000, the omission crosses the threshold and the six-year period applies.¹

A separate trigger applies to foreign financial assets. Omit more than $5,000 of income tied to assets that should have been disclosed under the foreign asset reporting rules and the six-year period applies whether or not the omission crosses the 25% test.¹ The dollar amount can be modest; the trigger is the reporting failure.

When There Is No Deadline at All

Three situations remove the statute of limitations entirely, giving the IRS 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.¹
No return filed. If a required return was never filed, the assessment period never starts. Filing the overdue return voluntarily does start the three-year clock, so there’s a real incentive to file even when you’re years behind.²
Unreported gifts. If a taxable gift that should have been shown 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 it at any time. Adequate disclosure starts the normal three-year period.³

The fraud exception is the one that shows up in practice, and the burden of proof falls on the IRS. The agency has to show by clear and convincing evidence that you intended to evade tax, not just that you made a mistake. A careless error, even a large one, is not fraud.

What Pauses or Extends the Clock

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

Notice of Deficiency

When the IRS sends a formal notice of deficiency, sometimes called a 90-day letter, the assessment clock stops automatically. The IRS cannot assess 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.⁴

If you petition, the freeze continues until the Tax Court’s decision becomes final, plus another 60 days.⁵ A Tax Court case that takes two years effectively adds that entire period to the assessment window. This happens by operation of law, not by choice.

Signed Consents to Extend

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

Form 872 sets a specific future expiration date. Once that date passes, the extension expires automatically and the IRS can no longer assess more tax for that year.⁶

Form 872-A is open-ended. There’s no expiration date; the extension stays in effect until either you or the IRS files Form 872-T to terminate it, at which point the IRS has 90 days to make any assessment.⁶

You are not legally required to sign either form. Refusing, though, often pushes the IRS to issue a notice of deficiency right away based on whatever information it has, which usually means a larger proposed adjustment than you would face if the examiner had time to review your documentation. Signing buys time on both sides and preserves your ability to negotiate before the IRS locks in a number.⁷

If you do agree to extend, ask for a fixed-date Form 872 rather than the open-ended 872-A when you can. The fixed date gives you a hard deadline and prevents the audit from running indefinitely. Both parties can also agree to restrict the consent to specific issues rather than the whole return, which limits what the IRS can revisit during the extension.⁶

Amended Returns Don’t Restart the Clock

Filing an amended return generally does not restart or extend the assessment deadline on your original return. The expiration date stays anchored to when you filed, or should have filed, the original.⁸

One narrow exception. If the IRS receives your amended income tax return during the final 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. It applies only to income tax returns and only to the changes on the amendment. It does not reopen the entire original return for a fresh look.⁸

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

Collection Is a Separate Ten-Year Clock

The audit window and the collection window are different, and mixing them up is a common mistake. Once the IRS formally assesses tax, whether from your original return, an amended return, or an audit, a separate ten-year collection period starts, known as the Collection Statute Expiration Date, or CSED.⁹

After ten years the IRS must generally stop collection efforts and any remaining balance expires.¹⁰ Certain actions pause that clock, including installment agreement requests, bankruptcy, offers in compromise, collection due process hearings, and innocent spouse claims.¹¹ Your specific CSED shows up in the “Transactions” section of your IRS account transcript.⁹

How Long to Keep Your Records

Match your record retention to the longest assessment period that could apply to you.¹²

At least three years from the filing date or due date, whichever is later, for a standard return.
Six years if you have foreign financial assets or any concern about potential underreporting.
Indefinitely if you didn’t file a return or filed a fraudulent one.

Property records deserve extra attention. Hold on to 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. Buy a rental property in 2015 and sell it in 2026, and you need those 2015 purchase records until at least 2029.¹²

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
Office of the Law Revision Counsel. 26 US Code 6213 – Restrictions Applicable to Deficiencies; Petition to Tax Court
5
Office of the Law Revision Counsel. 26 USC 6503 – Suspension of Running of Period of Limitation
6
Internal Revenue Service. IRM 25.6.22 Extension of Assessment Statute of Limitations by Consent
7
Internal Revenue Service. Publication 1035 – Extending the Tax Assessment Period
8
Internal Revenue Service. IRM 25.6.1 Statute of Limitations Processes and Procedures
9
Internal Revenue Service. Time IRS Can Collect Tax
10
GovInfo. 26 USC 6502 – Collection After Assessment
11
Taxpayer Advocate Service. Understanding Your Collection Statute Expiration Date
12
Internal Revenue Service. Topic No. 305, Recordkeeping