The IRS generally has three years from the date you file your tax return to initiate an audit — but this window extends to six years if you underreported income by more than 25%, and becomes unlimited if you filed a fraudulent return or failed to file altogether. Key Takeaways The standard IRS audit window is 3 years from the filing date or due date, whichever is later The statute extends to 6 years for substantial income understatements (over 25% omission) No statute of limitations applies to fraudulent returns or unfiled returns Signing Form 872 or 872-A can voluntarily extend the audit window The statute of limitations applies to assessments, not just audits The Standard 3-Year Rule Under Internal Revenue Code §6501(a), the IRS has three years from the date you filed your tax return to assess additional taxes. This period is called the Assessment Statute Expiration Date (ASED). If the IRS does not begin an audit or issue an assessment within this window, it generally cannot collect additional taxes for that year. The three-year clock starts on the later of two dates : The date you actually filed your return, or The original due date of the return (typically April 15) For example, if you filed your 2023 return on February 15, 2024, the statute still runs from April 15, 2024 — meaning the IRS has until April 15, 2027 to audit that return. If you filed late on August 1, 2024 (with an extension), the three-year period runs from August 1, 2024. The 6-Year Extended Statute IRC §6501(e) extends the assessment period to six years in three specific situations: 1. Substantial Omission of Income (25% Rule) If you omit from gross income an amount that exceeds 25% of the gross income stated on your return, the IRS gets...