The IRS can audit tax 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, and has no time limit if it suspects fraud.

The statute of limitations — the legal deadline for the IRS to audit you — depends on what the agency suspects and what you reported. For a straightforward audit where there are no red flags, the IRS has three years from the date you filed or the return's due date, whichever is later. If the IRS believes you significantly underreported your income, that window extends to six years. If the IRS suspects you committed tax fraud, there is no time limit at all.

Understanding which lookback period applies to you matters because it determines how far back you need to keep records and how exposed you are to an audit. The three-year window is the most common scenario. The six-year window is less common but still happens regularly. The unlimited fraud window is rare but serious.

Key Takeaways

  • The IRS can audit returns from the past three years under normal circumstances, measured from your filing date or the return's due date, whichever is later.
  • The lookback period extends to six years if the IRS suspects you underreported income by 25 percent or more, which is called a substantial understatement.
  • There is no time limit for audits involving suspected tax fraud, though the IRS must prove fraud occurred.
  • You should keep tax records and supporting documents for at least three years, and six years if you have significant self-employment income or investment activity.
  • The statute of limitations can be extended if you sign a consent form agreeing to extend it, which the IRS may request during an audit.

The Standard Three-Year Window

For most taxpayers, the IRS has three years to audit a return. This period starts on the later of two dates: the date you actually filed your return, or April 15 of the year after the tax year in question. If you filed your 2022 return on March 1, 2023, the three-year window runs from March 1, 2023, to March 1, 2026. If you filed late, say on October 15, 2023, the window runs from October 15, 2023, to October 15, 2026.

This three-year rule applies when there are no major discrepancies between what you reported and what the IRS's records show. The agency uses this period to spot-check returns for math errors, missing income that third parties reported (like W-2s or 1099s), and deduction claims that don't match IRS data. Most audits, if they happen at all, occur within this window.

After three years pass, the IRS generally cannot audit that return unless it uncovers evidence of fraud or a substantial understatement. This is why keeping records for three years is a common recommendation — after that point, you have less exposure to routine audits.

The Six-Year Window for Substantial Understatement

If the IRS believes you underreported your gross income by 25 percent or more, the statute of limitations extends to six years. This is called a substantial understatement of income. The six-year window gives the IRS more time to investigate because the agency views a 25 percent gap as a significant error or intentional omission, not a minor mistake.

A substantial understatement typically happens when you fail to report a large amount of income — for example, you received a 1099 for $50,000 in freelance income but only reported $30,000, or you omitted an entire income stream. The IRS catches these gaps by comparing third-party reports (W-2s, 1099s, K-1s) against what you filed. If the gap is large enough, the six-year rule kicks in automatically.

You do not need to do anything to trigger the six-year window — the IRS applies it on its own if it finds a substantial understatement during its initial review. If you are audited under this rule, the IRS will examine six years of returns rather than three, which means you need records going back further and the audit process takes longer.

The Unlimited Timeline for Suspected Fraud

If the IRS suspects you committed tax fraud — meaning you intentionally and knowingly underreported income or claimed false deductions — there is no statute of limitations. The IRS can audit returns from 10, 15, or even 20 years ago if it has evidence of fraud.

Fraud is a high bar. The IRS must prove not just that you made errors, but that you did so deliberately and with intent to evade taxes. Negligence, carelessness, or even recklessness is not fraud in the tax sense. The agency needs documentary evidence — hidden income, false receipts, offshore accounts, or a pattern of behavior — to pursue a fraud case. A single large error or omission usually does not trigger a fraud investigation on its own.

If the IRS opens a fraud investigation, it typically refers the case to the Criminal Investigation division, which is a serious matter. The agency may also pursue civil fraud penalties in addition to back taxes and interest. This is why the unlimited timeline exists — fraud is treated as a crime, not just a tax error.

How the Statute of Limitations Clock Works

The statute of limitations clock starts on the date you file your return or the return's due date, whichever is later. If you file early, the clock starts on your filing date. If you file late, the clock starts on the original due date (usually April 15), not your actual filing date. This means if you file your 2022 return on August 1, 2024, the three-year window still starts on April 15, 2023, not August 1, 2024.

The clock stops if you sign a consent form extending the statute of limitations. The IRS often requests this during an audit to give itself more time to investigate. You can refuse to sign, but doing so may prompt the IRS to issue a notice of deficiency and pursue collection more aggressively. In practice, most taxpayers sign the extension because it gives both sides more time to resolve the audit.

Once the statute of limitations expires, the IRS cannot assess additional taxes for that year. If you owe money, the IRS can still try to collect it, but it cannot conduct a new audit or add penalties related to that tax year.

What Records You Should Keep and for How Long

You should keep tax records for at least three years after filing. This includes your tax return itself, W-2s, 1099s, receipts for deductions, bank statements, and any other documents you used to prepare your return. Three years covers the standard audit window and protects you if the IRS initiates a routine examination.

If you have significant self-employment income, rental property income, or investment activity, keep records for six years. These areas are higher-risk for IRS scrutiny, and the six-year substantial understatement rule is more likely to apply. Self-employed people in particular should maintain detailed records of income and expenses going back six years.

For records related to property — home purchases, improvements, or sales — keep documentation indefinitely or at least until seven years after you sell the property. The IRS can challenge your cost basis and depreciation claims long after the initial purchase, so holding onto these records protects you.

What Triggers an Audit and Extends the Timeline

The IRS does not randomly audit most returns. Audits are triggered by specific red flags: income reported by third parties that does not match your return, unusually large deductions relative to your income, business losses claimed year after year, cash-intensive businesses, or returns filed by people in high-income brackets. If your return has one of these flags, the IRS is more likely to initiate an audit within the three-year window.

Once an audit begins, the IRS may request an extension of the statute of limitations. This is a Form 872, Consent to Extend the Time Limit for Assessment of Tax Liability. If you sign it, you are agreeing to give the IRS additional time — usually 90 days or more — to complete the audit. You can refuse to sign, but the IRS will then issue a notice of deficiency, which is a formal notice that you owe additional tax. At that point, you have the right to appeal in Tax Court, but the IRS can also begin collection proceedings.

If you do not respond to an IRS audit notice within the deadline, the IRS will issue a notice of deficiency automatically, which restarts the clock on your right to appeal. This is why responding to audit notices promptly is important — it keeps you in control of the timeline.

Frequently Asked Questions

Can the IRS audit a return from 10 years ago?

Only if the IRS suspects fraud. Under normal circumstances, the three-year statute of limitations means the IRS cannot audit a return more than three years old. If a substantial understatement is found, the window is six years. Fraud investigations have no time limit, but the IRS must prove intentional wrongdoing, not just errors or negligence.

Does filing an amended return restart the statute of limitations?

Filing an amended return (Form 1040-X) does restart the statute of limitations for that specific return. The new three-year window runs from the date you file the amended return, not the original filing date. This means amending a return can actually extend your exposure to audit, so amend only if you have a genuine error or omission to correct.

What happens if I do not keep records after three years?

If the IRS audits you and you cannot produce records to support your deductions or income, the IRS can disallow those items. You will owe back taxes, interest, and potentially penalties. Keeping records for at least three years protects you in case of an audit. For self-employment or investment income, six years is safer.

Can I ask the IRS to close an audit before the statute of limitations expires?

Yes. If you and the IRS agree on the audit findings, you can sign a Form 870, Waiver of Restrictions on Assessment and Collection of Deficiency in Tax, which closes the audit and allows the IRS to assess any additional tax owed. This ends the examination and prevents the IRS from reopening it for the same issues, though it does not prevent a separate audit of a different tax year.

What is the difference between the statute of limitations and the collection period?

The statute of limitations is the deadline for the IRS to assess additional tax. The collection period is how long the IRS has to collect taxes you owe after assessment. The collection period is typically 10 years, which is separate from the audit window. You can owe taxes long after the statute of limitations expires if the IRS assessed them before the deadline.