How Far Back the IRS Can Audit Your Tax Returns

The IRS can audit returns from the past three years in most cases, but can go back six or seven years under specific circumstances

The IRS has a statute of limitations — a legal time window — for how far back it can examine your tax returns. For most people, that window is three years from the date you filed or the return's due date, whichever is later. This means if you filed your 2021 return in April 2022, the IRS generally cannot audit it after April 2025.

However, the IRS can extend this window if it finds a substantial underreporting of income. If you reported less than 25 percent of your actual income on a return, the IRS can audit that return for up to six years instead of three. In rare cases involving fraud or a completely unfiled return, there is no time limit at all — the IRS can audit any year.

The specific years the IRS examines depend on what triggered the audit. If the agency is investigating a pattern across multiple years, it may request returns from several consecutive years, even if it focuses its examination on one or two of them.

Key Takeaways

The IRS can audit returns filed within the past three years under normal circumstances, measured from your filing date or the return's due date.
If you underreported income by 25 percent or more, the IRS can audit that return for up to six years instead of three.
Returns involving fraud or that were never filed have no time limit — the IRS can audit them at any point.
The statute of limitations can be extended if you and the IRS sign an agreement to keep the audit open longer.
State tax agencies often have their own separate time limits, which may be longer or shorter than the federal three-year window.

The three-year standard window and how it is calculated

The three-year rule is the default for most taxpayers. It runs from the later of two dates: the date you actually filed your return, or the return's official due date (usually April 15 for individual returns). If you filed your 2023 return on March 1, 2024, the three-year window closes on March 1, 2027. If you filed the same return on June 15, 2024, the window closes on June 15, 2027.

This means filing early does not protect you — the IRS counts from the due date if you file before it. Filing late, however, does extend the window slightly. If you file a return after the due date, the clock starts from your actual filing date, giving the IRS a longer period to audit.

The three-year window applies whether you owe money, are owed a refund, or break even. It also applies regardless of the return's complexity or the amount of income reported.

When the IRS can go back six or seven years

The IRS can extend its audit window to six years if it determines you underreported your income by a substantial amount. The threshold is 25 percent or more of the gross income you reported on the return. This is called the substantial understatement rule.

For example, if you reported $40,000 in income but actually earned $60,000, you underreported by $20,000 — which is 50 percent of what you reported. This triggers the six-year rule, and the IRS can audit that return for six years from the filing or due date.

The six-year window is less common than the three-year window because the IRS must first discover the underreporting and then prove it meets the 25 percent threshold. In practice, this usually happens during an audit of a more recent year when the IRS notices a pattern or receives information from a third party (like an employer or bank) showing unreported income.

Fraud and unfiled returns have no time limit

If the IRS suspects tax fraud — intentional misrepresentation or evasion — it can audit a return at any time, regardless of how many years have passed. Fraud means you knowingly and deliberately underreported income, claimed false deductions, or hid money. The burden of proof is on the IRS, and fraud cases are rare and serious.

Similarly, if you never filed a return for a particular year, the IRS has no statute of limitations. It can assess taxes, penalties, and interest for any unfiled year. This applies even if the IRS did not discover the missing return until decades later.

The IRS distinguishes between fraud and negligence or mistakes. Negligence — carelessness or lack of reasonable care — does not remove the time limit; the standard three-year or six-year window still applies. Only intentional fraud opens an unlimited window.

How the IRS chooses which years to examine

When the IRS initiates an audit, it typically selects specific tax years to examine. The agency may focus on one year or request returns from multiple consecutive years. The selection depends on what triggered the audit: a discrepancy on a recent return, a pattern the IRS noticed, or information from a third party.

If the IRS is investigating a specific issue — such as unreported business income or inflated charitable deductions — it may request returns from three to five years to establish a pattern. This does not mean the agency will audit all of those years equally; it may examine one or two closely and review the others more lightly.

The IRS publishes audit rates by income level and industry, but individual selection is not random. The agency uses computer algorithms to flag returns with unusual deductions, inconsistent reporting, or mismatches with third-party documents (W-2s, 1099s, mortgage interest statements).

Extending the statute of limitations through agreement

You and the IRS can agree in writing to extend the statute of limitations beyond the standard three, six, or unlimited years. The IRS often requests this extension during an active audit if it needs more time to complete its examination. You are not required to sign — you can refuse and the IRS must close the audit when the original deadline arrives.

If you sign an extension agreement, you receive a copy. The agreement specifies the new deadline and which tax years are covered. Many taxpayers sign these agreements because refusing can prompt the IRS to issue a preliminary assessment based on incomplete information, which is often less favorable than allowing more time for negotiation.

An extension agreement does not change the underlying rules about what the IRS can examine; it simply postpones the deadline. Once the extended deadline passes, the statute of limitations expires and the IRS cannot audit that year further.

State tax audits and their separate time limits

State tax agencies operate under their own statutes of limitations, which are separate from the federal three-year rule. Some states follow the federal three-year standard, while others allow four, five, or six years. A few states have no limit for fraud cases, similar to the federal rule.

Being audited by the IRS does not automatically trigger a state audit, but state agencies often review federal audit results. If the IRS adjusts your federal return, your state may open its own examination of the same years. The state's time limit applies independently — even if the federal statute has expired, the state may still be within its window.

You can contact your state tax agency directly to learn its specific statute of limitations. This information is usually posted on the agency's website or available by phone.

Frequently Asked Questions

Can the IRS audit a return after the three-year window closes?

Only in specific circumstances: if you substantially underreported income (25 percent or more), the window extends to six years. If fraud is involved or the return was never filed, there is no time limit. Otherwise, once three years pass, the IRS cannot audit that return.

Does filing my return late give the IRS more time to audit me?

Yes, slightly. The three-year window starts from your actual filing date if you file after the due date, rather than from the due date itself. This gives the IRS a few extra months. However, the difference is usually small — a few weeks to a few months depending on how late you filed.

What counts as substantial underreporting for the six-year rule?

Underreporting 25 percent or more of the gross income you reported on the return triggers the six-year rule. For example, if you reported $50,000 in income but earned $70,000, you underreported by 40 percent, which exceeds the threshold.

If I amend my return, does the statute of limitations reset?

Filing an amended return does not reset the original three-year clock. However, if you amend the return to report additional income or claim a larger refund, a new statute of limitations may begin for that amended portion. The rules are complex, and it depends on what you changed and when you filed the amendment.

How do I know if the IRS is currently within the statute of limitations for my return?

Count three years forward from your filing date or the return's due date, whichever is later. If that date has passed and the IRS has not contacted you, the standard window has closed. If you suspect underreporting or fraud occurred, the six-year or unlimited window may apply. Contact the IRS directly or consult a tax professional if you are uncertain.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.