The IRS can audit tax 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 look back depends on what they find — or what they suspect. For a routine audit of a return with no major problems, the agency typically has three years from the date you filed or the return's due date, whichever is later. If the IRS discovers you underreported your income by 25 percent or more, that window stretches to six years. If the IRS believes you committed tax fraud or filed no return at all, there is no deadline — they can audit you indefinitely.

Understanding which lookback period applies to you matters because it determines how far back you need to keep records and how much of your tax history could be examined. The three-year rule is the most common scenario, but the six-year rule catches more people than many realize, and the fraud exception is rare but serious.

Key Takeaways

  • The IRS has three years to audit most tax returns, measured from the filing date or the return's due date, whichever is later.
  • The lookback period extends to six years if the IRS finds you underreported income by 25 percent or more of what you actually reported.
  • There is no time limit for audits involving fraud or if you filed no return at all.
  • You should keep tax records and supporting documents for at least three years, and six years if you have self-employment income or rental property.
  • The IRS must notify you of an audit within the applicable time window; if they contact you after the deadline, you can challenge the audit's validity.

The Three-Year Standard Audit Window

For most taxpayers, the IRS has three years from the date you filed your return — or from the return's due date if you filed early — to begin an audit. This is called the statute of limitations. If you filed your 2021 return on April 15, 2022, the IRS could initiate an audit anytime up to April 15, 2025. If you filed the same return on February 1, 2022, the clock still starts on April 15, 2022, because that was the due date.

This three-year window is the default rule and covers the vast majority of audits. It applies whether the IRS is examining your W-2 income, deductions, credits, or a combination of items. The IRS does not need to explain why it selected your return; it simply needs to open the audit within the three-year window.

Once an audit begins, the IRS can take additional time to complete it. The three-year limit is about when they can start, not how long the process can take. An audit that begins in year three can stretch into year four or beyond.

When the IRS Can Look Back Six Years

If the IRS discovers that you underreported your gross income by 25 percent or more, the statute of limitations extends to six years. This is a significant jump and catches many self-employed people, freelancers, and those with investment income. The 25 percent threshold is measured against the income you actually reported on your return, not against what you should have reported.

For example, if you reported $40,000 in income but actually earned $60,000, you underreported by $20,000. That is 50 percent of what you reported, which exceeds the 25 percent threshold. The IRS can now audit that return up to six years from the filing date. If you reported $40,000 and earned $45,000, you underreported by $5,000, which is 12.5 percent — below the threshold, so the three-year rule applies.

The six-year rule does not require intent or negligence on your part. Even an honest mistake that results in a 25 percent underreporting can trigger it. This is why people with variable income, cash businesses, or multiple income sources should be especially careful with their reporting.

No Time Limit for Fraud or Unfiled Returns

If the IRS suspects you committed tax fraud — meaning you intentionally misrepresented your income, claimed false deductions, or hid money — there is no statute of limitations. The IRS can audit a return from 1995 if it has evidence of fraud. Fraud is a serious allegation and requires proof of intent, not just a mistake or negligence.

Similarly, if you did not file a return at all for a given year, the IRS has no deadline to assess tax on that year. They can send you a notice of deficiency decades later if they discover unreported income. This is one reason the IRS maintains records going back many years and why people sometimes receive notices about returns they never filed.

The fraud exception is uncommon in routine audits. The IRS must have substantial evidence — such as hidden bank accounts, false documents, or a pattern of deliberate misreporting — to pursue a fraud case. A simple error or even a large one does not automatically trigger a fraud investigation.

How the Statute of Limitations Starts and Stops

The clock starts on the later of two dates: the date you filed your return or the return's due date. If you file early, the due date is what counts. If you file late, the filing date is what counts. For most individual returns, the due date is April 15, but some people get extensions.

If you file a return with an extension — say you file on October 15 instead of April 15 — the statute of limitations still runs from April 15, the original due date. Filing late does not give you extra time; it only delays when the IRS can start an audit if they choose to.

The statute can be paused or extended in certain situations. If you sign an agreement with the IRS to extend the statute (called a Form 872), the deadline moves forward. If you file an amended return, a new statute of limitations may begin for the items you changed. If you are in an active dispute with the IRS, the clock may stop temporarily.

What Records You Should Keep and for How Long

The IRS recommends keeping tax records for at least three years, which aligns with the standard audit window. This includes your tax return, receipts, invoices, bank statements, and documentation for any deductions or credits you claimed. If you have self-employment income, rental property, or investment accounts, keep records for six years to cover the extended lookback period.

Some records should be kept longer. If you claim depreciation on property, keep records for as long as you own the property plus three years after you sell it. If you contribute to a retirement account, keep contribution records indefinitely. If you have a mortgage, keep the closing statement and records of improvements for as long as you own the home and for three years after you sell it.

Digital records are acceptable. The IRS does not require paper copies, so scanned documents, email confirmations, and bank statements downloaded as PDFs all count. What matters is that you can produce the records if the IRS asks.

What Happens If the IRS Contacts You After the Deadline

If the IRS sends you an audit notice after the statute of limitations has expired, you can challenge the audit's validity. You do not have to provide records or cooperate with an examination that falls outside the legal window. The burden is on the IRS to prove that the statute had not expired when they initiated the audit.

In practice, the IRS is careful about this deadline. They track when they send notices and ensure they are within the window. However, errors do happen, and if you receive a notice for a return that is clearly outside the three-year (or six-year) window, contact a tax professional or the IRS directly to clarify.

If you are unsure whether the statute has expired, calculate it yourself: take the filing date or due date, whichever is later, and add three years (or six years if you underreported income by 25 percent or more). If today's date is after that, the statute has likely expired, though exceptions exist for fraud or unfiled returns.

Frequently Asked Questions

Can the IRS audit a return from 10 years ago?

Only if they suspect fraud or if you did not file a return at all. For a normal audit, the IRS has three years, or six years if you underreported income by 25 percent or more. If neither applies, a 10-year-old return is outside the statute of limitations.

Does filing an amended return restart the statute of limitations?

Yes, in most cases. When you file an amended return, a new statute of limitations begins for the items you changed. The IRS then has three years (or six years, depending on the underreporting) to audit those specific items. Items you did not amend are still governed by the original deadline.

What if I did not file a return — how far back can the IRS go?

There is no limit. The IRS can assess tax on any year you did not file, no matter how long ago. If you have unfiled returns, it is worth filing them now, even if you owe tax, because it stops the IRS from assessing penalties indefinitely and may reduce the penalties you face.

Does the statute of limitations apply to refunds?

No. If you are owed a refund, you generally have three years to claim it from the original due date of the return. After three years, the IRS keeps the money. This is the opposite of the audit rule — the IRS has a longer window to audit you than you have to claim a refund.

If the IRS is auditing me, can they look at other years too?

Yes. An audit of one year does not limit the IRS to that year alone. If they find a pattern of underreporting or suspect fraud, they can expand the audit to other years within the statute of limitations. This is one reason it is important to be consistent and accurate across multiple years of returns.