Statute of Limitations on Federal Taxes: 3, 6, and 10-Year Rules

The statute of limitations on federal taxes sets three separate deadlines you need to know: the IRS generally has three years to audit a return you filed, ten years to collect a tax once it’s been assessed, and you have three years from filing (or two years from payment, whichever is later) to claim a refund. Several situations shorten, extend, or entirely remove these windows, so the deadline that actually applies to you depends on what happened on the return and what has happened since.

The Three-Year Audit Window

Under Internal Revenue Code § 6501, the IRS has three years to assess additional tax on a return you filed. Assessment is the formal act of recording a liability on the IRS’s books, and it has to happen before collection can begin. The clock starts on the later of the date you actually filed or the return’s due date. File early on March 10 for an April 15 return, and the three years run from April 15. File on extension in October, and the clock starts the day you filed.¹

Once the window closes, the IRS generally cannot audit that year or assess more tax for it. That’s why keeping records for at least three years after filing is the standard advice.

When the IRS Gets Six Years, or Unlimited Time

The three-year deadline stretches to six years when you leave off more than 25% of the gross income that should have appeared on your return. Report $74,000 when you earned $100,000, and you’ve crossed the threshold. Intent doesn’t matter here. A careless bookkeeping error that omits enough income triggers the same six-year window as a deliberate one.¹

Overstating your basis in property you sold counts the same way, because it shrinks the taxable gain you reported. Estate and gift tax returns get the same six-year treatment when more than 25% of the gross estate or total gifts is left off.¹

A separate six-year rule covers unreported income from foreign financial assets subject to FATCA reporting. If you omit more than $5,000 in income tied to those assets, the IRS gets six years regardless of whether the omission exceeds 25% of your total gross income.¹

In three situations there is no deadline at all:

No return filed. If you were required to file but didn’t, the assessment clock never starts. The IRS can pursue that year decades later. Filing the missing return is the only way to start the clock.
Fraudulent return. A return filed with intent to evade tax carries no time limit on assessment. The IRS must prove fraud by clear and convincing evidence, a higher standard than the “more likely than not” test used in most civil disputes.²
Willful attempt to evade tax. Separate from filing a fraudulent return, any willful attempt to defeat or evade tax also removes the time limit.

All three exceptions live in § 6501(c).¹

Being Asked to Sign an Extension

During an audit, the IRS may ask you to sign a consent form that extends the assessment deadline. This usually happens when the audit is running long and the statute is about to expire. You have the right to refuse.

Form 872 sets a fixed expiration date that both sides agree to. Form 872-A keeps the statute open indefinitely until either party files a termination notice (Form 872-T), after which the IRS has 90 days to finish.³ You can also negotiate an extension limited to specific issues rather than the whole return.

Refusing isn’t free. If the IRS is mid-audit and the statute is about to expire, the examiner may issue a notice of deficiency based on whatever information is on hand rather than give you more time to present your case. That said, an open-ended Form 872-A deserves real caution because it puts no outer boundary on when assessment can happen. If you agree to extend, consider limiting the consent to a fixed date or to the issues actually under review.⁴

Your Deadline to Claim a Refund

Statutes of limitations cut both ways. You have your own deadline to claim a refund of overpaid tax, called the Refund Statute Expiration Date (RSED). Miss it and the money is gone permanently, even if the IRS agrees you overpaid.

You must file the refund claim by the later of three years from the date you filed the return, or two years from the date you paid the tax. If you filed early, the IRS treats the return as filed on its due date for this purpose. Withheld income tax and estimated payments are considered paid on the original due date.⁵

Timing also caps how much you can get back. File within the three-year window and your refund is limited to the tax you paid during the three years before filing, plus any extension period. Miss that but file within two years of payment, and the refund is limited to what you paid in those two years. This lookback rule catches people off guard. You might be owed $5,000 but only recover $2,000 because the rest was paid outside the lookback period.⁶

A few exceptions allow more time. A bad debt or worthless security loss gives you seven years from the return due date. Taxpayers in a Presidentially declared disaster area may get an extra year. If you’re physically or mentally unable to manage your financial affairs due to a condition expected to last at least 12 months or result in death, the refund deadline is suspended for the period of that disability.⁵

The Ten-Year Collection Period

Once the IRS has assessed a tax, a second clock starts. The agency has ten years to collect, and this deadline is called the Collection Statute Expiration Date, or CSED. After the CSED passes, the IRS loses its legal authority to pursue the debt and the balance is written off.⁷

The ten years run from the date of assessment, not the date you filed or the return’s due date. Assessment sometimes happens within weeks of filing, but it can also occur years later if additional tax is determined through an audit. Each assessment gets its own CSED, so you may have different expiration dates for different tax years or even for different adjustments within the same year. A 2023 return assessed in June 2024 has a CSED in June 2034; a later audit assessment for the same year in March 2026 has its own CSED in March 2036.

How to Find Your CSED

You can look up your CSED on an IRS account transcript. Sign in to your IRS Online Account, or request a transcript by filing Form 4506-T or calling 800-908-9946. Because tolling events (below) can complicate the math, you can also call 800-829-1040 for individuals or 800-829-4933 for businesses and ask the IRS to confirm the exact CSED for a specific tax period.⁸

Events That Pause the Collection Clock

Certain events temporarily suspend the collection statute. While the clock is paused, whatever time is lost gets added to the end of the original deadline, pushing the CSED out by months or years.

Bankruptcy. Filing for bankruptcy triggers an automatic stay that stops IRS collection. The clock pauses for the duration of the bankruptcy plus six months after it concludes.⁹

Offer in Compromise. Submitting an OIC pauses collection from the date the offer is pending until it’s accepted, withdrawn, returned, or rejected. If rejected, the pause continues 30 more days, and through any appeal filed within that window.¹⁰

Collection Due Process hearing. Requesting a CDP hearing pauses the collection period from the date the IRS receives the request until the determination is final or you withdraw. If you take it to Tax Court, the pause continues through the litigation.¹¹

Installment agreement request. Asking for an installment agreement pauses the clock while the request is pending. If the IRS rejects or terminates it, the pause continues 30 more days plus any timely appeal.⁸

Innocent spouse relief. Filing for innocent spouse relief pauses the CSED for the requesting spouse until they file a waiver or the 90-day window to petition Tax Court expires, whichever comes first. If they do petition, the clock stays paused through the final decision. An additional 60 days is added in both scenarios. The other spouse’s CSED is unaffected.⁸

Notice of deficiency. When the IRS issues a notice of deficiency (the 90-day letter), the assessment statute is suspended for the 90 days you have to petition Tax Court, plus 60 more days. If you file, the suspension continues through the litigation. The IRS cannot assess while the case is pending.¹²

Living outside the United States. The collection clock pauses whenever you’re continuously outside the country for six months or more. If fewer than six months remain when you return, the IRS gets at least six months from your return date to resume.⁹

People with large tax debts sometimes assume that filing for an installment plan or submitting an offer buys time. It does, but the collection clock stops the entire time those requests are pending. An OIC that takes 18 months to process followed by an installment agreement that runs a year before termination has added roughly two and a half years to the CSED. That’s worth weighing if you’re close to the end of the ten-year window.

How Amended Returns Affect the Deadline

Filing an amended return generally does not restart or extend the three-year assessment period. The deadline is still measured from the original return’s filing date or due date. There is one narrow exception: if the IRS receives a signed amended income tax return within the last 60 days before the assessment deadline expires, the IRS gets 60 days from receipt to assess any additional tax shown on it. This 60-day rule applies only to income tax returns, not to employment, excise, estate, or gift tax returns.¹³

An amended return does not reopen the tax year for a full new audit. The IRS may review the changes on it, but the original assessment deadline governs unless one of the exceptions above applies.

Criminal Prosecution Is on a Separate Clock

The civil deadlines above are separate from criminal prosecution. Under § 6531, the general statute of limitations for criminal tax offenses is three years from the commission of the offense, extended to six years for more serious conduct including tax evasion, filing a fraudulent return, and willfully failing to file a required return or pay tax.¹⁴ A closed civil window does not by itself mean the criminal window is closed, and vice versa.

1
Office of the Law Revision Counsel. 26 USC 6501 – Limitations on Assessment and Collection
2
Internal Revenue Service. IRM 25.1.6 Civil Fraud
3
Internal Revenue Service. IRM 25.6.22 Extension of Assessment Statute of Limitations by Consent
4
Internal Revenue Service. Consent to Extend the Time to Assess Tax
5
Internal Revenue Service. Time You Can Claim a Credit or Refund
6
Office of the Law Revision Counsel. 26 USC 6511 – Limitations on Credit or Refund
7
Office of the Law Revision Counsel. 26 USC 6502 – Collection After Assessment
8
Internal Revenue Service. Time IRS Can Collect Tax
9
Office of the Law Revision Counsel. 26 USC 6503 – Suspension of Running of Period of Limitation
10
Taxpayer Advocate Service. Collection Statute Expiration Date CSED
11
Internal Revenue Service. IRM 5.1.9 Collection Appeal Rights
12
Internal Revenue Service. IRM 4.8.9 Statutory Notices of Deficiency
13
Internal Revenue Service. IRM 25.6.1 Statute of Limitations Processes and Procedures
14
Office of the Law Revision Counsel. 26 USC 6531 – Periods of Limitation on Criminal Prosecutions