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 standard window of three years from the date you file or the due date of your return — whichever is later — to audit your tax return. This is called the statute of limitations. If you filed early, the clock starts from the official due date, not the date you submitted. If you filed late, it starts from when you actually filed.

However, this three-year window is not absolute. The IRS can extend the lookback period to six years if it finds you underreported your income by 25 percent or more. In rare cases involving fraud or a completely unfiled return, there is no time limit at all — the IRS can audit you indefinitely.

Understanding which years are vulnerable and what triggers a longer audit window helps you know what records to keep and what to expect if the IRS contacts you.

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, whichever is later.
If you underreported income by 25 percent or more, the IRS can go back six years instead of three.
Fraud or a completely unfiled return removes the time limit entirely, allowing the IRS to audit any year with no deadline.
You should keep tax records and supporting documents for at least three years, and six years if you reported business income or claimed deductions you want to defend.

The Three-Year Standard Audit Window

For most taxpayers, the IRS has three years from the filing deadline to initiate an audit. If you filed your 2022 return on April 15, 2023, the three-year window closes on April 15, 2026. If you filed that same return early in February 2023, the window still closes on April 15, 2026 — the official due date, not your early filing date.

This three-year period applies to routine audits where the IRS questions deductions, income reporting, or credits you claimed. The IRS does not need to tell you why it selected your return for audit within this window — it can simply open an examination and request documents.

After three years pass, the IRS generally cannot audit that year unless it discovers one of the circumstances that extends the deadline. Once the deadline passes, you are protected from examination of that return.

When the IRS Can Go Back Six Years

If the IRS determines that you underreported your gross income by 25 percent or more, it can extend the audit window to six years. This is a substantial underreporting — not a small math error or a missed line item, but a significant gap between what you reported and what the IRS believes you actually earned.

The IRS calculates this threshold based on your total gross income for the year. If your actual gross income was $100,000 but you reported only $70,000, that is a 30 percent underreport, which triggers the six-year window. The IRS can then audit that return up to six years from the filing or due date.

This extended window applies only to the specific year in question. Your 2021 return might fall under the six-year rule while your 2022 return remains under the three-year rule. The IRS must have evidence of the substantial underreporting before it can use the six-year deadline — it cannot simply assume underreporting and then investigate.

Fraud and Unfiled Returns Have No Time Limit

If the IRS suspects fraud — intentional misrepresentation or deliberate evasion of taxes — the statute of limitations does not apply. The IRS can audit a return filed 10, 15, or 20 years ago if it has evidence of fraudulent activity. Fraud includes falsifying documents, hiding income sources, or claiming false deductions with intent to deceive.

A completely unfiled return also has no time limit. If you never filed a return for a particular year, the IRS can assess taxes and penalties for that year at any time. This applies even if decades have passed. However, the IRS typically focuses on more recent unfiled years first, as the practical burden of auditing very old returns is high.

Fraud is a serious allegation and requires substantial evidence. Mistakes, poor record-keeping, or even aggressive deductions do not automatically constitute fraud. The IRS must prove intent to defraud, not merely that you made an error.

How to Calculate Which Years Are Still Open

To determine whether a specific return is still within the audit window, start with the filing due date — April 15 for most individual returns, unless you received an extension. Add three years to that date. If today's date falls before that three-year mark, the return is still open under the standard window.

For example, if you filed your 2020 return on April 15, 2021 (on time), the three-year window closes on April 15, 2024. If it is now 2025, that return is closed unless the IRS found substantial underreporting or fraud.

If you filed an extension, the due date is October 15, not April 15. A 2020 return filed under extension on October 15, 2021, would have a three-year window closing on October 15, 2024. The extension changes the deadline, which changes when the audit window closes.

What Records to Keep and for How Long

The IRS recommends keeping tax records for at least three years. This includes your filed return, receipts, invoices, bank statements, and documentation for any deductions or credits you claimed. After three years, you can generally discard these records safely — unless your return falls into a category with a longer audit window.

If you are self-employed, own a business, or claimed significant deductions, keep records for six years. Business records, depreciation schedules, and expense documentation should be retained longer because business audits are more common and the six-year window applies more frequently in these cases.

For unfiled returns or years you suspect may have issues, keep records indefinitely. If the IRS contacts you about a year you thought was closed, having original documents is your strongest defense.

What Happens If the IRS Contacts You About an Old Return

If the IRS sends you a notice about a return outside the normal three-year window, the first step is to verify that the audit is actually within the legal deadline. Check the filing date and the notice date. If the notice arrives more than three years after you filed, ask the IRS to explain why — it should cite substantial underreporting, fraud, or an unfiled return.

You have the right to dispute the IRS's authority to audit that year. If the IRS cannot justify extending the deadline, you can request that the examination be closed. This is a formal process, and you may want to consult a tax professional or contact the IRS Taxpayer Advocate Service if you believe the audit is outside the legal window.

Do not ignore a notice simply because you think the deadline has passed. The IRS may be correct that an exception applies. Respond to the notice and raise the statute of limitations issue in writing if you believe it is relevant.

Frequently Asked Questions

Can the IRS audit me for a return I filed 10 years ago?

Only if the IRS has evidence of fraud, you never filed that return, or you substantially underreported income by 25 percent or more. Under normal circumstances, the audit window closes after three years. If the IRS contacts you about a 10-year-old return, ask them to explain which exception applies.

Does filing an extension change when the audit window closes?

Yes. The three-year window is measured from the official due date, not your filing date. If you filed an extension, your due date is October 15 instead of April 15, so the audit window closes three years from October 15. This actually gives the IRS an extra six months to audit compared to someone who filed on time in April.

If I amend an old return, does that restart the audit clock?

Filing an amended return (Form 1040-X) can restart the statute of limitations for that year. The three-year window begins again from the date you file the amendment. This is one reason to be cautious about amending very old returns — you may reopen a year that was previously closed to audit.

What if I cannot find my records from three years ago?

If the IRS audits that year, you can request copies of documents from the IRS or your financial institutions. Banks keep records for seven years. However, missing records make it harder to defend your deductions. If you cannot substantiate what you claimed, the IRS may disallow those deductions and assess additional tax.

Does the statute of limitations apply to tax debt I already owe?

The statute of limitations on assessment (when the IRS can audit) is different from the statute of limitations on collection (when the IRS can collect a debt). The IRS generally has 10 years to collect a tax debt from the date it is assessed. Even if the audit window closes, you may still owe the tax.

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.