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 more years if it suspects underreported income

The statute of limitations is the legal time window during which the IRS can audit you. For most people, that window is three years from the date you filed 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 start an audit.

The three-year rule is not absolute. The IRS can reach back six years if it believes you underreported your income by 25 percent or more. It can go back even further — sometimes indefinitely — if it suspects fraud or if you did not file a return at all. Understanding which rule applies to you depends on what the IRS finds during its examination.

Key Takeaways

The standard audit window is three years from when you filed or the return was due, whichever is later.
The IRS can audit six years back if it suspects you underreported income by 25 percent or more on that return.
There is no time limit if the IRS believes you committed tax fraud or did not file a return at all.
The clock starts over if you file an amended return, and the IRS can audit that amended return within three years of filing it.
State tax agencies often have their own statute of limitations, which may be longer than the federal three-year window.

The three-year standard audit window

For most tax returns, the IRS has three years to begin an audit. This period runs from the later of two dates: the date you actually filed your return, or the return's official due date (usually April 15 for individual returns). If you filed early, the clock starts from the due date. If you filed late, it starts from when you filed.

This three-year window applies whether the IRS is examining your return for math errors, deductions it questions, or income it wants to verify. Once three years have passed without the IRS opening an audit, it generally cannot go back and examine that return. The IRS must notify you in writing that an audit is beginning before the three-year deadline expires.

When the IRS can audit six years back

If the IRS suspects you underreported your income by 25 percent or more, it can audit returns going back six years instead of three. "Underreported" means the income you reported on your return was significantly less than what the IRS believes you actually earned. The 25 percent threshold is calculated against the income you did report, not the income the IRS thinks you should have reported.

For example, if you reported $40,000 in income but the IRS believes you earned $60,000, that is a 50 percent underreport, which triggers the six-year rule. The IRS does not need proof of fraud to use this extended window — it only needs to suspect substantial underreporting. This rule applies to individual returns, business returns, and partnership returns.

Fraud and unfiled returns have no time limit

The IRS can audit you indefinitely if it believes you committed tax fraud. Fraud means you intentionally and knowingly underpaid your taxes — for instance, by reporting false deductions, hiding income, or submitting forged documents. The IRS does not have to prove fraud beyond a reasonable doubt the way a criminal court would; it only has to show that you acted with fraudulent intent.

Similarly, if you never filed a tax return for a particular year, there is no statute of limitations. The IRS can assess taxes and penalties for unfiled years going back as far as it has records. This is one reason the IRS sometimes pursues people for returns from 10, 15, or even 20 years ago — because those years were never filed in the first place.

How amended returns restart the clock

If you file an amended return using Form 1040-X, you start a new three-year audit window for that amended return. The clock runs from the date you file the amendment, not from the original return's due date. This means amending an old return can actually extend the period during which the IRS can audit you.

For example, if you filed your 2020 return on time in April 2021, the standard three-year window would end in April 2024. But if you file an amended 2020 return in June 2024, the IRS now has three years from June 2024 — until June 2027 — to audit that amended return. The IRS can examine both the original return and the changes you made on the amendment.

State tax audits often have longer windows

Most states follow the federal three-year rule, but some allow longer audit periods. California, for instance, generally allows four years. New York allows three years for most returns but six years if it suspects substantial underreporting. A few states have no statute of limitations for fraud cases, just like the federal government.

If you are audited by both the IRS and your state, the state audit may continue after the federal audit closes. The state is not bound by the federal statute of limitations. You should check your state's tax agency website or contact them directly to learn the specific rules for your state, because being outside the federal window does not protect you from a state examination.

What happens when you receive an audit notice

An audit notice from the IRS will specify which tax year or years are being examined and what the IRS wants to review. The notice will also tell you whether the audit is a correspondence audit (handled by mail), an office audit (you go to an IRS office), or a field audit (the IRS visits your home or business). You have the right to representation — you can have a tax professional, attorney, or certified public accountant handle the audit on your behalf.

The IRS must complete its examination and send you a formal notice of any proposed changes within the statute of limitations period. If the IRS misses the deadline, it generally loses the right to assess additional taxes for that year. However, if you sign a waiver extending the statute of limitations, you give the IRS more time to finish the audit.

Frequently Asked Questions

Can the IRS audit a return that is more than three years old?

Yes, if it suspects underreporting of 25 percent or more, it can audit six years back. If it suspects fraud or you never filed, there is no time limit. But for a standard examination with no red flags, three years is the normal window.

Does filing an amended return give the IRS more time to audit me?

Yes. Filing an amended return starts a new three-year clock from the date you file the amendment. If you amend an old return close to the end of the original audit window, you may extend the period the IRS can examine that year.

What if I filed my return late — does that change when the audit window closes?

The three-year window runs from whichever is later: your actual filing date or the return's due date. If you filed six months late, the clock still starts from your filing date, not the original due date.

Can my state audit me after the IRS audit closes?

Yes. State audit windows are separate from federal windows and may be longer. A state can audit you even if the IRS has finished and closed your case for that same year.

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

Contact a tax professional or attorney immediately. If the IRS is reaching back beyond three years, it likely suspects underreporting or fraud. You have the right to representation, and having professional help from the start protects your interests.

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.