The IRS can audit returns from the past three years in most cases, but can go back six years if it suspects you underreported income by 25 percent or more

The IRS has a time limit called the statute of limitations, which sets how long after you file a return the agency can audit you. For most people, that limit is three years from the date you filed or the return's due date, whichever is later. If you filed early, the clock starts from the due date, not the filing date.

The three-year window is the standard rule. However, the IRS can extend that period to six years if it finds you reported less income than you actually earned and the underreported amount is at least 25 percent of your reported gross income. There is no statute of limitations at all if the IRS suspects fraud or if you did not file a return.

Key Takeaways

  • The IRS normally has three years from your filing date or the return's due date to audit you, whichever comes later.
  • The agency can go back six years if it suspects you underreported income by 25 percent or more of your stated gross income.
  • If you did not file a return at all, or if the IRS suspects criminal fraud, there is no time limit on how far back it can go.
  • Filing an amended return does not reset the statute of limitations clock for that original return year.

When the Three-Year Limit Applies

The three-year statute of limitations covers most audits. This means if you filed your 2021 return on April 15, 2022, the IRS generally cannot audit that return after April 15, 2025. The clock runs from the due date of the return, not the date you actually filed it.

The three-year window applies even if you owe taxes or the IRS owes you a refund. Once the three years pass, the IRS cannot assess additional tax on that return, and you cannot claim a refund for that year either. The statute closes the door on both directions.

The Six-Year Rule for Substantial Underreporting

If the IRS determines you reported less than 75 percent of your actual income, it can audit that return up to six years after filing. This is called the substantial underreporting rule. The threshold is 25 percent of your reported gross income, not 25 percent of the underreported amount.

For example, if you reported $40,000 in income but actually earned $60,000, you underreported by $20,000. That $20,000 is 50 percent of your reported income, which exceeds the 25 percent threshold. The IRS could audit that return up to six years out. The six-year period still runs from your filing date or the return's due date, whichever is later.

No Time Limit for Unfiled Returns and Fraud

If you never filed a return for a particular year, the statute of limitations does not apply. The IRS can go back as far as it wants to assess tax, penalties, and interest on that year. The agency can also pursue unfiled years indefinitely, though in practice it usually focuses on the most recent years.

If the IRS suspects you committed tax fraud — meaning you intentionally and knowingly underreported income or claimed false deductions — there is also no statute of limitations. Fraud cases are rare and require proof of willful intent, not just mistakes or negligence. The IRS must prove fraud in court, and the burden is high.

How the Statute Starts and Stops

The statute of limitations clock starts on the later of two dates: the date you filed your return or the return's official due date. If you file your 2023 return on January 15, 2024, the clock starts January 15, 2024, not April 15, 2024. If you file late, say on July 1, 2024, the clock still starts April 15, 2024 — the due date.

The clock can be paused or extended if you sign a consent form agreeing to extend the statute. The IRS sometimes asks taxpayers to sign these forms during an audit. Signing extends the deadline, usually by six months or a year. You can refuse to sign, but doing so may prompt the IRS to issue a notice of deficiency and pursue the case in Tax Court.

Amended Returns and the Statute of Limitations

Filing an amended return does not reset the statute of limitations for the original return year. If you filed your 2021 return on April 15, 2022, and then file an amended return on March 1, 2025, the statute of limitations still expires on April 15, 2025 — three years from the original filing date. The amended return does not give the IRS extra time to audit.

However, if you file an amended return after the statute has already expired, the IRS can still examine the items you changed on that amended return. The amended return itself opens a new three-year window for the specific changes you made, even if the original return is closed.

What Happens After the Statute Expires

Once the statute of limitations expires, the IRS loses the legal right to assess additional tax on that return. If the agency sends you a notice after the deadline has passed, you can challenge it by citing the expired statute. The IRS must stop collection efforts and cannot pursue the debt further.

The statute expiration does not erase the debt or forgive it — it simply means the IRS cannot legally collect it. If you owe money and the statute expires, you are no longer required to pay that particular year's tax. However, the IRS can still pursue other years that remain open.

Frequently Asked Questions

Can the IRS audit me for a return I filed five years ago?

Only if it suspects you underreported income by 25 percent or more. Otherwise, the three-year statute of limitations would have expired. The IRS must have evidence of substantial underreporting to extend the audit window to six years.

Does filing an amended return restart the statute of limitations?

No. The statute runs from the original filing date, not the amended filing date. However, the amended return itself may open a new three-year window for the specific items you changed, even after the original return's statute has expired.

What if I never filed a return for a year?

The statute of limitations does not apply. The IRS can go back as far as it wants to assess tax and penalties on unfiled years. In practice, the agency typically focuses on the most recent unfiled years, but legally it has no time limit.

Can the IRS extend the statute of limitations without my permission?

No. The IRS can only extend the statute if you sign a consent form. You can refuse to sign, but the IRS may then issue a notice of deficiency and take the case to Tax Court instead.

Does the statute of limitations apply to refunds?

Yes. You have three years from the filing date to claim a refund. If you file a return and the statute expires, you cannot claim a refund for that year even if you overpaid taxes.