The IRS can audit returns from the past three years in most cases, but can go back six years if it finds a substantial underreporting of income, and has no time limit if it suspects fraud.

The length of time the IRS can audit you depends on what they find and how serious the issue is. For a routine audit where there are no major problems, the agency has three years from the date you filed your return or the return's due date — whichever is later. That three-year window is called the statute of limitations, and it's the most common scenario.

If the IRS discovers that you underreported your income by 25 percent or more, the statute of limitations extends to six years. This is sometimes called the "substantial underreporting" rule. The IRS measures this threshold against the income you actually reported on your return, not what you should have reported.

If the IRS suspects fraud or criminal tax evasion, there is no time limit at all. The agency can go back as far as it wants. This is rare and requires evidence of intentional wrongdoing, not just mistakes or negligence.

Key Takeaways

  • The IRS has three years from your filing date to audit most returns, which covers the vast majority of audits.
  • The audit window extends to six years if you underreported income by 25 percent or more on a single return.
  • If the IRS suspects fraud, it can audit returns with no time limit, though this requires evidence of intentional tax evasion.
  • The statute of limitations clock starts from your filing date or the return's due date, whichever is later.
  • You should keep tax records and supporting documents for at least three years, and longer if you have concerns about underreporting.

The Three-Year Standard for Most Audits

The three-year statute of limitations is the default rule for federal income tax audits. This means the IRS generally cannot examine a return more than three years after you filed it or after the return's due date, whichever comes later. If you filed your 2020 return on time in April 2021, the three-year window closes in April 2024. If you filed late, the clock still starts from the actual due date, not your filing date.

This three-year period applies to most routine audits — situations where the IRS questions deductions, credits, or income amounts but does not suspect intentional wrongdoing. The IRS initiates the majority of audits within the first two years after filing, so most people never experience an audit at all, and those who do usually hear about it relatively soon after filing.

When the IRS Can Audit Six Years Back

If you underreported your gross income by 25 percent or more, the statute of limitations extends from three years to six years. The IRS measures this threshold strictly: it compares the income you reported on your return to your actual income, not to what you claimed as deductions or adjustments. A 25 percent underreporting of a $50,000 reported income means you failed to report at least $12,500 in income.

This six-year rule applies to that specific return only. If you filed multiple returns, each one has its own statute of limitations. The six-year window still begins from your filing date or the return's due date, whichever is later. The IRS must have concrete evidence of the underreporting — usually from third-party documents like W-2s, 1099s, or bank records — to invoke the six-year rule.

No Time Limit When Fraud Is Suspected

If the IRS suspects you committed tax fraud or criminal tax evasion, the statute of limitations does not apply. The agency can audit returns from decades ago. Fraud means you intentionally and knowingly underpaid your taxes — not that you made an honest mistake, misunderstood a rule, or even claimed something you shouldn't have. The IRS must have evidence of deliberate deception, such as hiding income, inflating deductions you knew were false, or maintaining two sets of books.

Criminal tax cases are rare and are handled by the IRS Criminal Investigation division, not the regular audit division. The IRS must build a strong case and often works with the Department of Justice before pursuing criminal charges. Civil fraud cases, which do not result in criminal prosecution, also have no time limit but require clear evidence of intentional wrongdoing.

How the Statute of Limitations Clock Works

The statute of limitations begins on the later of two dates: the date you actually filed your return or the return's official due date. If you filed your 2022 return in February 2023, the clock starts in February 2023, not April 2023. If you filed on time in April 2023, the clock still starts in April 2023. The key is that the IRS uses the later date, so filing early does not shorten the window.

The clock can be paused or extended in certain situations. If you sign a consent form agreeing to extend the statute of limitations — sometimes called a Form 872 — you give the IRS additional time to complete an audit. You are not required to sign this form, but the IRS may close the case if you refuse. If you file an amended return, the statute of limitations for that amended return starts fresh from the date you filed the amendment.

What Records You Should Keep and for How Long

The IRS recommends keeping tax records for at least three years after filing, which aligns with the standard statute of limitations. This includes your tax return itself, W-2s, 1099s, receipts for deductions, bank statements, and any other documents that support the numbers on your return. If you claim a home office deduction, charitable contributions, or business expenses, keep the receipts and documentation that back up those claims.

If you have concerns that you may have underreported income or if you are self-employed or run a business, consider keeping records for six years. The same applies if you have substantial investment income or rental property income, since these are areas the IRS audits more frequently. If you suspect you may have made a serious error on a return, keeping records longer gives you the option to file an amended return within the statute of limitations.

What Happens If the Statute of Limitations Has Expired

Once the statute of limitations expires, the IRS cannot assess additional tax on that return. If you receive an audit notice for a return outside the statute of limitations window, you can challenge it by citing the expiration date. However, the IRS rarely audits returns that are already outside the window unless fraud is involved.

If you owe back taxes from a return within the statute of limitations, the IRS can pursue collection even after the assessment period ends. The collection statute of limitations is separate and typically runs ten years from the date the tax was assessed. This means the IRS can collect on a debt long after it can no longer audit the return that created the debt.

Frequently Asked Questions

Can the IRS audit a return from 10 years ago?

Only if the IRS suspects fraud or criminal tax evasion. For routine audits, the standard three-year window applies, and the six-year window applies only if you underreported income by 25 percent or more. Without evidence of intentional wrongdoing, the IRS cannot audit a return that is more than six years old.

Does filing an amended return restart the statute of limitations?

Yes. When you file an amended return (Form 1040-X), the statute of limitations for that amended return starts fresh from the date you file the amendment. This means if you amend a 2020 return in 2024, the IRS has three years from 2024 to audit the amended return, not from the original 2020 filing date.

What if I filed my return late — does that change when the IRS can audit?

The statute of limitations is based on the later of your actual filing date or the return's due date. If you filed late, the clock still starts from the official due date (usually April 15), not from when you actually filed. Filing late does not extend the IRS's audit window.

If I refuse to sign a Form 872, can the IRS still audit me?

The IRS can continue an audit that is already underway, but if you refuse to sign a Form 872 (which extends the statute of limitations), the IRS must close the case before the statute of limitations expires. You have the right to refuse, but doing so may result in the IRS issuing a notice of deficiency based on the information it has gathered so far.

How do I know if an audit notice is valid if it's for an old return?

Check the filing date on the return in question and count forward three years (or six years if substantial underreporting is claimed). If the audit notice arrives after the statute of limitations has expired, you can respond by citing the expiration date. Keep a copy of your original return and filing confirmation to prove when you filed.