How Long Can Taxes Be Audited: 3 Years, 6 Years, or No Limit

In most cases, the IRS has three years from the date you file to audit a tax return and assess additional tax. That window stretches to six years if you left out a substantial amount of income, and it disappears entirely if you filed a fraudulent return or never filed at all. How long taxes can be audited depends on which of these situations applies to your return.¹

The Standard Three-Year Rule

Federal law gives the IRS three years after you file a return to assess additional tax for that year.² The clock’s start date depends on when and how you filed.

File early, and the IRS treats the return as filed on the original due date. A return sent in February for an April 15 deadline starts its three-year clock on April 15, not the day it arrived.³

File under an extension, and the rule flips. An extended due date is not treated the same as April 15. If you send your return in August during your extension period, the three-year clock begins on the date the IRS receives it. Filing during the extension period rather than waiting until October 15 can actually shorten the audit window.³

The return also has to qualify as a genuine attempt to report your income and calculate your tax. If a document is missing a signature, income figures, or required schedules, the IRS may take the position that no valid return was ever filed. Without a valid return, the three-year clock never starts. Keep W-2s, 1099s, and receipts for at least three years after your filing date to cover most situations. Once the window closes, the IRS is generally barred from assessing additional tax for that year.¹

Six Years for Substantial Income Omissions

The audit window doubles to six years when you leave a significant amount of income off your return. The threshold: if the unreported income is more than 25 percent of the gross income you did report, the IRS gets six years instead of three.² The calculation uses gross income before deductions or credits.

If you reported $100,000 in gross income but actually earned $130,000, the $30,000 gap is 30 percent of what you reported. That crosses the line, and the IRS has six years to assess additional tax, interest, and penalties. The extended window applies whether the omission was intentional or accidental.¹

Two situations often trigger the six-year rule without the taxpayer noticing:

Overstating your cost basis when you sell property or investments. Inflating what you originally paid understates your gain, and that understatement counts as an omission from gross income for purposes of this rule.²
Failing to report more than $5,000 in income tied to foreign financial assets that should have been disclosed. When this happens, the six-year window applies regardless of whether the 25 percent threshold was crossed.²

Taxpayers with rental income, brokerage accounts, or freelance work face a higher risk of accidentally crossing the threshold because income arrives from multiple sources and is easier to miss.

Situations With No Time Limit

A few circumstances remove the deadline entirely, leaving the return open to audit at any point in the future.

Fraudulent Returns

If you file a false or fraudulent return with the intent to evade tax, the IRS can assess additional tax at any time. There is no deadline.² Fraud takes more than a careless mistake. The IRS has to show deliberate deception, such as keeping two sets of books, fabricating invoices, or systematically hiding income, and the burden of proof falls on the government.

Returns You Never Filed

The three-year clock only starts once a valid return is on file. Skip the filing, and the clock never starts. The IRS can pursue that year’s taxes indefinitely.¹ The agency can demand a return, assess whatever tax it believes you owe, and add failure-to-file penalties and interest running back to the original due date. Filing a late return starts the clock and eventually gives you the protection of a closed statute.

Inadequately Disclosed Gifts

Gift tax returns follow their own version of the rule. If a reportable gift is left off a gift tax return, or described so vaguely that the IRS cannot tell what was given, there is no time limit on assessing gift tax for that transfer.² The standard three years only applies when the gift is disclosed with enough detail for the IRS to evaluate it, typically including the property, the parties, their relationship, and how the value was determined.⁴

When the IRS Asks You to Extend the Window

During an active audit, the IRS may ask you to sign Form 872, which extends the assessment deadline past the normal three-year or six-year period. This request usually appears when an audit is approaching the statute’s expiration and the agency wants more time to finish.⁵

You have three options in response:

Refuse to sign. The IRS cannot penalize you for declining, and refusal does not count as failure to cooperate. The agency may then issue a notice of deficiency based on the information it has, which could be less favorable than a completed audit.
Agree to a limited extension covering only specific issues under examination, rather than the whole return.
Negotiate a shorter extension date than the one the IRS proposed.

Both sides have to agree on the final terms. A related form, Form 872-A, creates an open-ended extension with no fixed end date, and because it stays in effect until one party terminates it (plus 90 days), it carries more risk than a fixed-date consent.⁵

Collection Runs on a Separate Ten-Year Clock

Once the IRS finishes an audit and assesses additional tax, a different deadline governs how long it has to collect. The agency has ten years from the date of assessment to collect through levies, liens, wage garnishment, or court action.⁶ This is called the Collection Statute Expiration Date, or CSED.⁷

Several common actions pause the ten-year clock and effectively give the IRS more time:⁸

Requesting an installment agreement pauses the clock during review and for 30 days after a rejection or proposed termination.
Submitting an offer in compromise pauses it from submission until the IRS decides, plus 30 days.
Filing bankruptcy pauses it from the petition date until the case closes, is dismissed, or is discharged, plus six months.
Requesting a collection due process hearing pauses it through appeals and for up to 90 days after a final determination.
Filing for innocent spouse relief pauses it while the claim is pending, plus 60 days.
Living continuously outside the United States for six months or more generally pauses it for that period.

If you owe a large balance and are weighing an installment agreement or offer in compromise, keep in mind that seeking relief also extends the IRS’s collection reach.

State Audit Periods Are Different

State revenue agencies set their own audit timelines. Many follow the federal three-year standard, but some states use a four-year baseline, and the rules on when the clock starts and what exceptions apply vary. Check your own state’s statute rather than assuming it mirrors the federal window.

A federal audit adjustment usually triggers additional state time. When the IRS reports unreported income or disallows a deduction, it passes that information to state tax authorities. Most states then give you a window (commonly 90 to 180 days) to file an amended state return reflecting the federal changes. Miss that deadline, and the state typically has extra time (often one to two years from the federal notice) to adjust your state return on its own. Only the items affected by the federal change are supposed to be reopened; the state generally cannot use the federal adjustment to reexamine unrelated parts of your return from that year.

Your Deadline to Claim a Refund

The statute of limitations runs in both directions. You have your own deadline to claim a refund for overpaid tax: three years from the date you filed the return, or two years from the date you paid the tax, whichever is later.⁹ If you never filed a return, only the two-year rule from the payment date applies.

Miss the deadline and you lose the refund, even if you genuinely overpaid. The IRS has no authority to override it. This matters most for taxpayers who skip filing in years when they would have been owed money. A separate rule extends the refund period to seven years when the claim relates to a deduction for a bad debt or a worthless security.⁹

1
Internal Revenue Service. Time IRS Can Assess Tax
2
Office of the Law Revision Counsel. 26 USC 6501 – Limitations on Assessment and Collection
3
Internal Revenue Service. Statute of Limitations Processes and Procedures
4
Internal Revenue Service. Estate and Gift Tax Examinations
5
Internal Revenue Service. Extension of Assessment Statute of Limitations by Consent
6
Office of the Law Revision Counsel. 26 USC 6502 – Collection After Assessment
7
Internal Revenue Service. Collection Statute Expiration
8
Internal Revenue Service. Time IRS Can Collect Tax
9
Office of the Law Revision Counsel. 26 USC 6511 – Limitations on Credit or Refund