The IRS can audit returns from the past three years in most cases, but can go back six years or longer if they find substantial underreporting of income or suspect fraud.
The standard statute of limitations for an IRS audit is three years from the date you filed your return or the return's due date, whichever is later. This means if you filed your 2021 return on time in April 2022, the IRS generally has until April 2025 to begin an audit. After that window closes, the IRS cannot assess additional tax on that year.
However, this three-year window is not absolute. The IRS can extend the lookback period significantly if they identify problems with your return, and understanding when and why they do this matters for how long you need to keep records and what to prepare for.
Key Takeaways
- The IRS has three years from your filing date to audit most returns, but this period can be extended if they find errors or unreported income.
- If you underreported your income by 25 percent or more, the IRS can audit returns from up to six years back.
- Suspected fraud or a completely unfiled return has no statute of limitations — the IRS can audit those years indefinitely.
- Keeping tax records and supporting documents for at least six years protects you if an audit occurs outside the standard three-year window.
When the IRS can extend the audit window to six years
The IRS can look back six years instead of three if they find that you substantially underreported your income — generally meaning you reported less than 75 percent of your actual income on the return. This is sometimes called the six-year rule, and it applies to the specific year in question, not your entire tax history.
For example, if you earned $100,000 in 2020 but reported only $70,000, that is a substantial underreporting. The IRS could audit your 2020 return even if you filed it in April 2021 and it is now 2027. The six-year window would run from your filing date, so they would have until April 2027 to begin the audit.
The IRS does not need to prove intent or fraud to use the six-year rule — they only need to show that the underreporting was substantial. This is why income discrepancies flagged by third parties (like employers or banks reporting 1099 forms) often trigger extended audits.
Fraud and unfiled returns have no time limit
If the IRS suspects tax fraud, there is no statute of limitations. They can audit any year, going back as far as they want, as long as they can build a case that you intentionally misrepresented your tax liability. Fraud is a serious allegation and requires evidence of deliberate wrongdoing, not just mistakes or negligence.
Similarly, if you never filed a return for a particular year, the IRS can assess tax for that year at any time. There is no deadline. This applies even if the statute of limitations has passed for years you did file.
The IRS rarely pursues audits for years older than ten years unless there is evidence of fraud or a pattern of non-filing, but the legal authority to do so exists indefinitely.
How the IRS selects returns to audit
The IRS does not audit randomly. They use computer screening to flag returns with unusual patterns, and they prioritize cases based on the potential tax recovery and the strength of the evidence. Returns with large deductions relative to income, self-employment income, rental property losses, or significant charitable contributions are audited more frequently than W-2 wage earners with standard deductions.
Third-party reporting mismatches are one of the most common triggers. If your employer reports $80,000 in wages on a W-2 but you report $70,000 on your return, the IRS's matching system will flag it. The same happens with 1099 forms from clients, banks reporting interest income, or investment firms reporting capital gains.
Audits initiated years after filing are usually triggered by these kinds of discrepancies or by a related audit — for instance, if the IRS audits your 2022 return and finds problems, they may expand the audit to include 2021 and 2023 as well.
What records you should keep and for how long
Keep all tax records and supporting documents for at least six years. This includes receipts, invoices, bank statements, cancelled checks, W-2s, 1099s, mortgage statements, charitable donation records, and any other documentation you used to prepare your return. If you are self-employed or have rental income, keep records even longer — seven to ten years is standard practice.
The six-year guideline covers the extended audit window and gives you proof if the IRS questions deductions or income. For years outside the six-year window, you can generally discard records, though some people keep them indefinitely for their own records.
Digital copies are acceptable, but make sure they are legible and stored securely. If the IRS requests records during an audit, you will need to produce them quickly, so organize them by year and category.
What happens if the IRS audits a year outside the standard window
If the IRS contacts you about a return filed more than three years ago, it usually means they found a substantial underreporting or a third-party mismatch. The audit process itself works the same way — they will request specific documents, ask questions about deductions or income, and either accept your return as filed or propose changes.
You have the right to respond to any audit notice, regardless of how old the return is. If you disagree with their findings, you can appeal through the IRS Appeals Office or dispute the assessment in Tax Court. Having organized records makes this process much simpler.
If the IRS assesses additional tax from an older year, you will owe the tax plus interest calculated from the original due date. Penalties may also apply if the IRS finds negligence or substantial underreporting, though penalties are separate from the tax itself.
State tax audits and their own time limits
State tax audits operate on their own timelines, which vary by state. Most states follow a three-year statute of limitations similar to the federal rule, but some allow four or five years, and a few allow longer. If you are audited by your state, the state's rules apply to state returns, separate from any federal audit.
A federal audit does not automatically trigger a state audit, but if the IRS makes changes to your federal return, you may need to file an amended state return. Some states automatically adjust your state tax based on federal changes; others require you to report the change yourself.
Frequently Asked Questions
Can the IRS audit me for a return I filed ten years ago?
Only if they suspect fraud, you substantially underreported income (by 25 percent or more), or you never filed a return for that year. For a standard return with no major red flags, the three-year window is the limit. If they do audit an older year, they must have evidence of the problem before they contact you.
If I amend an old return, does that restart the audit clock?
No. Filing an amended return does not restart the statute of limitations on the original return. However, if you amend a return to report additional income or claim a larger deduction, that amended return has its own three-year window from the date you filed the amendment. The IRS can audit the amended portion separately.
What if I discover I made a mistake on a return from five years ago?
You can file an amended return (Form 1040-X) at any time to correct errors. If you owe additional tax, filing the amendment voluntarily before the IRS contacts you may reduce or eliminate penalties. If you are owed a refund, you generally have three years from the original due date to claim it.
Does the audit statute of limitations pause if I request an extension?
No. Requesting an extension to file your return does not change the statute of limitations. The clock runs from your return's due date, not from when you actually filed it. If your return was due April 15 but you filed on October 15 with an extension, the three-year window still starts from April 15.
What should I do if I receive an audit notice for a year older than three years?
Do not ignore it. Respond to the notice within the timeframe given, provide the documents requested, and keep copies of everything you send. If you believe the audit is outside the statute of limitations, you can raise that issue in your response or during the audit process. The IRS must justify why they are auditing a year outside the standard window.