The assessment statute of limitations: the three-year rule under IRC 6501 and its exceptions

The general rule

IRC 6501(a) says that tax “shall be assessed within 3 years after the return was filed (whether or not such return was filed on or after the date prescribed)”. The period runs to the assessment, not to the start of an exam or the issue of a report. Pub 1035 puts it plainly: the IRS cannot assess additional tax after the period has expired, even if it discussed the need for an adjustment with the taxpayer before the expiration. The IRS calls the last day the assessment statute expiration date (ASED).

The 6501(a) definition of “return” is the return required to be filed by the taxpayer, not the return of a person from whom the taxpayer received an item. A partner's own Form 1040 starts the partner's period; the partnership's Form 1065 does not, although for the six-year omission rule a partner who lists the partnership on Schedule E is treated as disclosing the partnership's gross income (IRM 25.6.1.9.5.3, citing Harlan v. Commissioner). Partnership-level adjustments under the centralized audit regime have their own period; see the BBA statute of limitations.

When the clock starts

IRM 25.6.1.9.3 warns that the IRS received date does not always establish the filing date. The rules that most often move it:

The last row matters for nonfiler clients: an IRS-prepared return under 6020(b) “shall not start the running of the period of limitations on assessment and collection.” Only the taxpayer's own valid return does. Our statute date calculator applies these rules.

Amended returns generally do not restart or extend the period. IRM 25.6.1.9.4.2 says: “Filing an amended return doesn't usually extend the Assessment Statute Expiration Date (ASED).” The exception is IRC 6501(c)(7): if the IRS receives a signed amended income tax return showing more tax within the last 60 days before the ASED, it has 60 days from receipt to assess the additional tax shown. The rule applies only to subtitle A income tax, not employment, excise, gift or estate tax.

What counts as a return

A document starts the period only if it is a valid return. IRM 25.6.1.9.4.1 lists the elements: enough data to calculate the tax, it purports to be a return, it is an honest and reasonable attempt to satisfy the law, and it is signed under penalties of perjury. The IRS will not process an unsigned income tax return; it sends it back for signature. A return on the wrong form can still be valid if it has enough data to compute the liability. For the effect of filing a joint return after separate returns, see IRM 25.6.1.9.4.4.

Those four elements are the Beard test. In Beard v. Commissioner, 82 T.C. 766 (1984), aff'd 793 F.2d 139 (6th Cir. 1986), the Tax Court distilled the Supreme Court's cases into a test with four parts: “First, there must be sufficient data to calculate tax liability; second, the document must purport to be a return; third, there must be an honest and reasonable attempt to satisfy the requirements of the tax law; and fourth, the taxpayer must execute the return under penalties of perjury.” The altered Form 1040 in Beard, which reported wages and then backed them out as nontaxable receipts, failed the third element, so it was not a return and the period never started. The same test decides whether a protest filing, a form with an altered jurat, or a late original return filed after a substitute for return is a return for IRC 6501 purposes. The other half of the rule comes from Zellerbach Paper Co. v. Helvering, 293 U.S. 172 (1934): a return that meets the test starts the period even if it is wrong, because “Perfect accuracy or completeness is not necessary to rescue a return from nullity, if it purports to be a return, is sworn to as such” and reflects an honest effort to comply, and a later amended return “does not toll a limitation which has once begun to run.” IRM 25.6.1.9.4.2 follows Zellerbach, as discussed above.

Exceptions that lengthen or remove the period

Fraud reaches further than clients expect. Under IRM 25.6.1.9.5.2, “In the case of a joint return, the fraud of one spouse will keep the assessment period open with respect to both spouses.” A later non-fraudulent amended return does not start the period (Badaracco v. Commissioner, 464 U.S. 386 (1984)). The government bears the burden of proving fraud; the penalty side is covered in the civil fraud penalty.

Whose fraud counts: the preparer-fraud split. The courts are divided on whether IRC 6501(c)(1) is triggered by a third party's intent to evade when the taxpayer had none.

• In Allen v. Commissioner, 128 T.C. 37 (2007), the parties agreed the preparer claimed false deductions with intent to evade tax and the taxpayer did not know; the Tax Court held the period stays open because the statute “keys the extension to the fraudulent nature of the return, not to the identity of the perpetrator of the fraud.”
• In City Wide Transit, Inc. v. Commissioner, 709 F.3d 102 (2d Cir. 2013), an accountant filed fraudulent employment tax returns and amendments for the company to embezzle the tax savings; the Second Circuit reversed the Tax Court and held that the accountant intentionally evaded taxes, triggering 6501(c)(1), so the company's Forms 941 for seven quarters could be assessed at any time.
• In BASR Partnership v. United States, 795 F.3d 1338 (Fed. Cir. 2015), the government relied on the fraud of an outside attorney who structured the transactions but did not prepare the return; the Federal Circuit affirmed the Court of Federal Claims and held that the 6501(c)(1) suspension applies only when the taxpayer, not a third party, has the intent to evade, finding Allen unpersuasive and distinguishable.
• In Murrin v. Commissioner, No. 24-2037 (3d Cir. Aug. 18, 2025, amended Oct. 17, 2025), the taxpayer stipulated that her preparer intended to evade tax while she did not; the Third Circuit sided with the Tax Court, holding that because the statute is agnostic about who must intend to evade, taxpayer intent is not required.

The IRS follows Allen. IRM 25.6.1.9.5.2 states that for purposes of IRC 6501(c)(1) “fraud is not limited to the fraud of the taxpayer” and that the exception may apply where someone affiliated with the return, such as a preparer, committed the fraud even if the taxpayer did not know, but it limits the rule to returns the IRS can show were prepared with fraudulent intent and tells employees to consult Counsel. For a client whose refund suit or Tax Court appeal would lie in the Federal Circuit (Court of Federal Claims cases), BASR is binding; in the Second and Third Circuits the preparer's fraud is enough; elsewhere the Tax Court will apply Allen and the appellate question is open.

The six-year rule in detail

IRM 25.6.1.9.5.3 (rev. 10-01-2026) applies IRC 6501(e). The period becomes six years if the taxpayer omits more than 25% of the gross income stated on the return, or more than $5,000 of income attributable to foreign financial assets reportable on Form 8938 (whether or not the form was filed). Points practitioners need:

1. For a trade or business, gross income means gross receipts before cost of sales, so a business with thin margins can omit a large share of profit without crossing 25%.
2. An item adequately disclosed on the return or an attached statement is not omitted, if the disclosure apprises the IRS of its nature and approximate amount. That rule does not protect an overstatement of basis.
3. An overstatement of basis that understates gross income counts as an omission for returns filed after July 31, 2015, and for periods still open on that date (IRC 6501(e)(1)(B)(ii), discussed below).
4. Once the six-year period applies, it “applies to all items affecting the amount of income taxes owed, not just the omitted items.”
5. Compare an amended return against the original (or the last timely superseding return), not against another amended return.

Item 3 reverses a Supreme Court decision. In United States v. Home Concrete & Supply, LLC, 566 U.S. 478 (2012), the Court held, following Colony, Inc. v. Commissioner, 357 U.S. 28 (1958), that a taxpayer who overstates basis and so understates gain has not omitted an amount from gross income, so the six-year period in IRC 6501(e)(1)(A) did not apply, and the regulation Treasury had issued to adopt the IRS's reading did not change the result. Congress answered in 2015. IRC 6501(e)(1)(B)(ii) now provides: “An understatement of gross income by reason of an overstatement of unrecovered cost or other basis is an omission from gross income”, and the adequate-disclosure rule in 6501(e)(1)(B)(iii) is written to exclude basis overstatements, so disclosing the basis on the return does not help. Section 2005(b) of Pub. L. 114-41 applies the change to returns filed after July 31, 2015, and to earlier returns whose assessment period had not expired on that date. Home Concrete therefore governs only returns whose period had already closed by then; for anything a practitioner is likely to see now, a basis overstatement that understates gross income by more than 25% opens six years.

The IRS will not usually rely on the six-year rule to let the three-year period lapse. IRM 25.6.22.2.1 warns examiners that if they let the normal period expire relying on the 25% rule and the omission turns out to be 25% or less, the deficiency is barred. In practice that means a request for Form 872 even in cases where the IRS believes the six-year rule applies.

Events that suspend the period

Disaster relief works differently. IRC 7508A does not suspend the period; it lets the IRS specify a period of up to one year to be disregarded in determining whether acts listed in IRC 7508(a)(1), which include “Assessment of any tax”, were performed on time for taxpayers it determines are affected by a federally declared disaster, significant fire, or terroristic or military action. IRM 25.6.1.9.6.5 and 25.6.1.9.6.6 describe this as a postponement of the assessment deadline for up to one year. The postponement is defined by the IRS's disaster announcement and applies only to taxpayers within it, so check the announcement before treating a disaster-area client's ASED as moved; see disaster postponements.

The notice of deficiency suspension applies even to a notice later found invalid: IRM 4.8.9.24.4 notes that no exception is made in IRC 6503(a) for invalid notices, and the suspension continues even if the notice is rescinded under IRC 6212(d). See the notice of deficiency.

How the IRS protects the statute

IRM 4.10.2.2.1 makes examiners responsible for identifying and protecting the statute on returns in their custody, and adds: “Failure to protect the statute of limitations can result in disciplinary action.” That explains the internal deadlines that shape every exam:

The policy behind these deadlines is Rev. Proc. 57-6, which IRM 25.6.22.2.1 cites for the rule that consents are sought “only in cases involving unusual circumstances.” Whether to sign a requested extension is covered in Form 872 statute extensions; how the statute interacts with Appeals is covered in Appeals and the statute.

When the IRS assesses after the ASED

IRM 25.6.1.13 defines a barred assessment as one the IRS did not make before the ASED and says that after the ASED “the IRS generally cannot assess the amount unless a law or procedure extends, suspends, or otherwise keeps the ASED open.” If an assessment posts anyway, the remedy depends on whether it has been paid.

• Unpaid. IRC 6404(a)(2) authorizes the IRS to abate the unpaid portion of any assessment that “is assessed after the expiration of the period of limitation properly applicable thereto”. IRM 25.6.1.10.1.1 confirms that this includes an assessment made after the ASED. Request the abatement in writing with the ASED computation (return received date, any Form 872, any suspension) and the account transcript showing the assessment date (TC 290 or 300). IRC 6404(b) says there is no right to file a claim for abatement of income, estate or gift tax, so frame the request as an administrative request and, if it is refused, use audit reconsideration or a CDP hearing to raise the statute.
• Paid. IRC 6401(a) defines an overpayment to include tax “assessed or collected after the expiration of the period of limitation properly applicable thereto”, so a paid barred assessment is recovered by a refund claim within the IRC 6511 period and, if denied, a refund suit.
• Invalid notice of deficiency. IRM 4.8.9.12.4 says that if the notice is invalid and the assessment statute has expired, assessments based on it “cannot be made and, if already made, must be abated”, with a barred statute report on Form 3999.

Internally, a barred assessment is reported on Form 9355 or Form 3999 and investigated as an employee error (IRM 25.6.1.13; IRM 4.10.2.2.1). That is why a statute challenge gets attention: raise it as soon as the transcript shows an assessment date after the computed ASED.

The refund statute is separate

The refund statute under IRC 6511 runs on its own clock: a claim generally must be filed within three years of the return or two years of payment, whichever is later, with a look-back limit on the amount. A claim does not hold the assessment statute open. IRM 25.6.22.2.1 is explicit: “Claims for refund do not extend the statutory period for assessing additional tax.” Agreeing to a Form 872 does extend the refund window to match under IRC 6511(c), which is one of the reasons a taxpayer with a claim may want an extension. See refund claims and suits.

Questions practitioners ask