The IRS audit statute of limitations determines how far back the agency can reach to examine your returns and assess additional tax. Most taxpayers fall under the standard 3-year window, but certain situations extend that window significantly, sometimes with no limit at all.
What Is the Standard 3-Year Audit Window?
Under IRC Section 6501(a), the IRS has three years from the later of the return's due date or actual filing date to assess additional tax.
For a 2025 Form 1040 due April 15, 2026 and filed on that date, the IRS has until April 15, 2029. If you filed the same return early, in February 2026, the clock still starts April 15, 2026 because that was the due date.
Key points about the standard window:
- Filing an extension (Form 4868) extends the time to file, not the assessment period. The 3-year clock runs from the original due date for returns filed before or on the extended deadline.
- If you file late, the 3-year period starts from the actual filing date, not the due date.
- A late-filed return starts the clock. A return that was never filed does not.
When Does the IRS Get 6 Years?
IRC Section 6501(e) extends the assessment period to six years when you omit more than 25% of your gross income from a return.
Situations that can trigger the 6-year rule:
- Self-employment or 1099 income not reported on Schedule C
- Rental income substantially underreported
- Sale proceeds omitted from Schedule D
- Foreign income not disclosed on the return
The IRS measures the omission against gross income, not net income. If a return shows $300,000 of gross income and $90,000 was omitted, that is a 30% omission, which triggers the extended period.
There is a separate 6-year trigger for foreign financial assets: under IRC Section 6501(e)(1)(A)(ii), omitting more than $5,000 of income attributable to a specified foreign financial asset also extends the period to six years, regardless of the 25% threshold.
When Is There No Statute of Limitations?
Two situations create an unlimited assessment window under IRC Section 6501(c):
Fraudulent return. Under IRC Section 6501(c)(1), if a return was filed with fraudulent intent to evade tax, there is no statute of limitations. The IRS must prove fraud, but there is no time bar if it does.
No return filed. Under IRC Section 6501(c)(3), if a return was never filed for a particular year, the statute of limitations never begins. The IRS can assess tax for that year at any point in the future. Filing late, even years after the fact, does start the clock.
If you have unfiled years, the practical priority is to get those returns filed to begin the limitations period. The IRS cannot close the window on an unfiled year on its own.
How Do Foreign Information Return Failures Affect the Statute?
Missing foreign information returns can hold the statute of limitations open on your entire Form 1040, not just the foreign portions.
Under IRC Section 6501(c)(8), if you failed to file a required foreign information return, the assessment period for the full 1040 does not begin running until the missing return is filed. Returns affected include:
- Form 5471 (controlled foreign corporations)
- Form 3520 (foreign gifts and trusts)
- Form 8938 (FATCA reporting)
- Form 8865 (foreign partnerships)
- Form 8858 (foreign disregarded entities)
A single unfiled Form 5471 can leave an otherwise complete 1040 open indefinitely. If you realize you missed a required foreign information return, filing it (or an amended return that includes it) starts the clock.
What About Claiming a Refund?
The statute of limitations for claiming a refund is governed by IRC Section 6511. You can file an amended return and claim a refund within the later of:
- Three years from the date you filed the original return
- Two years from the date you paid the tax
If you miss both windows, the refund claim is barred regardless of whether the IRS could still audit you.
How Long Should You Keep Tax Records?
Keep records for at least as long as the applicable statute of limitations:
- Standard situations: 3 years from the filing date
- Self-employment, rental income, or any possible 25% omission risk: 6 years
- Foreign accounts, foreign information filing requirements, or unfiled years: indefinitely until those periods are clearly closed
Records needed include the return itself, all supporting documents (W-2s, 1099s, receipts, bank statements), and any correspondence with the IRS.
If you have received an IRS notice, see our guide on responding to a CP2000 notice for how the IRS typically initiates correspondence and what your response deadlines are.
Have questions about an IRS notice or want to know whether a prior year is still open? Contact TS CPA for a free consultation. We respond within the same day.