The IRS can audit 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 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 operates under different rules depending on what it suspects you did wrong, and understanding those rules matters because they determine how far back your records need to go and how serious the situation is.

Key Takeaways

  • The IRS has three years from your filing date to audit most returns, but this period extends to six years if income was underreported by 25 percent or more.
  • There is no time limit for audits involving fraud or if you did not file a return at all.
  • The IRS rarely audits returns older than three years unless it has specific reason to suspect a larger problem.
  • Keeping records for at least six years protects you if the IRS questions your return later.

The six-year rule for substantial underreporting

If the IRS believes you left off more than 25 percent of your gross income, the statute of limitations extends to six years instead of three. This is called the substantial underreporting rule, and it applies whether the underreporting was intentional or a mistake.

For example, if your actual gross income was $100,000 but you reported only $70,000, you have underreported by 30 percent. The IRS could audit that return up to six years after you filed it. The IRS does not need to prove you meant to hide the income — the size of the gap alone triggers the longer window.

This rule is why the IRS often starts by asking for income documentation: bank statements, 1099 forms, and records from employers. If those documents show significantly more income than what you reported, the six-year clock begins.

No time limit for fraud or unfiled returns

If the IRS suspects tax fraud — meaning you deliberately and knowingly filed a false return — there is no statute of limitations. The IRS can audit you 10, 15, or 20 years later if it has evidence you committed fraud.

The same applies if you never filed a return at all. The IRS can go back as far as it wants to assess tax on years you should have filed but did not. This is why the IRS sometimes sends notices for returns from a decade or more in the past.

Fraud is a high bar. The IRS must show you acted with intent to evade tax, not simply that you made errors or claimed deductions you should not have. However, once the IRS alleges fraud, the three-year and six-year limits no longer apply.

How the IRS decides which years to examine

The IRS does not audit randomly. It uses computer screening to flag returns that match certain patterns: unusually high deductions for your income level, business losses year after year, cash-based businesses, or income that does not match third-party reports like W-2s and 1099s.

When the IRS opens an audit, it typically focuses on the year you filed, but it can expand the examination to adjacent years if it finds problems. For instance, if you are audited for 2022 and the IRS discovers you overstated business expenses that year, it may also examine 2021 and 2023 to see if the pattern continues.

The IRS is more likely to reach back beyond three years if the initial audit uncovers something significant. A single mistake on one return usually does not trigger a multi-year examination, but evidence of a pattern or a large discrepancy often does.

What records you should keep and for how long

The safest approach is to keep tax records for at least six years. This covers you if the IRS uses the substantial underreporting rule and gives you documentation for any deductions or income you claimed. Records include receipts, invoices, bank statements, mortgage interest statements, charitable donation records, and anything else that supports what you reported.

For business owners, the stakes are higher. Keep business records — ledgers, profit-and-loss statements, payroll records, and receipts — for at least seven years. Businesses are audited more frequently than individual returns, and the IRS often examines multiple years at once.

If you are missing records from years the IRS is asking about, tell the IRS immediately. You can reconstruct some records using bank statements or third-party documents, and the IRS has procedures for handling missing documentation. Hiding the fact that records are gone or claiming they were destroyed looks worse than admitting you do not have them.

What happens after the statute of limitations expires

Once the statute of limitations closes, the IRS cannot assess additional tax for that year. If you are in the middle of an audit and the deadline passes, the IRS must stop examining that year and issue a closing letter.

However, the statute does not erase the year from your tax history. If you claimed a loss or credit on that return, and you carry it forward to later years, the IRS can still examine how you used it on subsequent returns. For example, if you claimed a business loss in 2021 that you carried forward to reduce income in 2022, the IRS can audit 2022 and question how you calculated the loss, even if 2021 is outside the statute window.

The statute also does not prevent the IRS from using information from an old return to support an audit of a newer one. If your 2019 return shows a pattern of overstated deductions, the IRS can use that as context when auditing your 2023 return.

Frequently Asked Questions

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

Only if you did not file a return for that year, if the IRS suspects fraud, or if the examination is part of a broader investigation into your tax history. For a normal return filed on time, the IRS has a three-year window, or six years if substantial income was underreported. After that, it cannot assess additional tax.

Does the statute of limitations reset if I file an amended return?

Filing an amended return does not reset the original statute of limitations for the year you are amending. However, if you file an amended return after the original deadline has passed, the statute may be extended for the amended portion. The safest approach is to assume the original deadline still applies and keep records accordingly.

What should I do if the IRS contacts me about a return from five years ago?

Respond promptly and gather the records that support what you reported. If the return is within the three-year window, the IRS is operating within its normal authority. If it is beyond three years, the IRS must have a reason — either substantial underreporting, fraud, or an unfiled return. Ask the IRS which years it is examining and why, so you understand what it is looking for.

If I owe back taxes, does the statute of limitations stop the IRS from collecting?

No. The statute of limitations prevents the IRS from assessing new tax after the deadline, but it does not stop collection of tax already assessed. The IRS can collect on a debt indefinitely through wage garnishment, bank levies, or liens, though it has its own collection statute of 10 years from the date of assessment.