Understanding IRS Statutes of Limitations

You have deadlines in your tax dispute. But so does the IRS. Three separate clocks are ticking right now, and understanding them changes how you approach every stage of your case.

These clocks determine how long the IRS can audit your return, how long it can collect a debt, and how long you have to claim a refund. Each one is governed by a different section of the Internal Revenue Code, and each one can be extended, suspended, or eliminated entirely depending on what happens in your case.

One term you will see throughout: assessment means the IRS officially records a tax liability on its books. Until assessment happens, the IRS cannot send bills or take collection action. Think of it as the IRS formally saying "you owe this amount."

The Three Clocks

Three distinct statutes of limitations govern IRS tax disputes:

The assessment statute must expire (or assessment must occur) before the collection clock begins. The refund statute runs independently based on when you filed or paid.

Think of it as a timeline: you file your return, which starts the assessment clock. If the IRS audits and assesses additional tax, that assessment starts the collection clock. Meanwhile, your refund clock has been running since you filed.

The Assessment Statute: How Long the IRS Has To Audit You

The General Rule: 3 years

Under IRC § 6501(a), the IRS must assess any tax within 3 years after the return was filed. The clock starts from the later of the return due date (including extensions) or the date you actually filed. A return filed early is treated as filed on the due date.

Example: Your 2023 return was due April 15, 2024. You filed on time. The IRS has until April 15, 2027 to assess additional tax. If you filed late on August 1, 2024, the deadline moves to August 1, 2027.

After the assessment statute expires, the IRS cannot assess additional tax for that year. Period. If the IRS contacts you about a year whose ASED has expired, respond in writing citing the statute expiration. The IRS's own policy (IRM 4.2.1.14) prohibits soliciting payment of a time-barred deficiency.

The 6-Year Rule: Substantial Omissions

The assessment period extends to 6 years when you omit from gross income an amount exceeding 25% of the gross income stated on your return. This comes from IRC § 6501(e).

A few important details:

• For business income, "gross income" means total receipts before cost of goods sold—not net profit. This catches more taxpayers than you might expect.
• An overstatement of basis counts as an omission of income. If you claimed $100,000 basis on a stock sale when the actual basis was $50,000, the $50,000 difference is treated as omitted income.
• Items adequately disclosed on the return or an attached schedule do not count as omissions.
• Foreign asset omissions exceeding $5,000 also trigger the 6-year period if reporting was required.

The IRS itself acknowledges this: "If we identify a substantial error, we may add additional years. We usually don't go back more than the last six years." (IRS Audits)

When There Is No Time Limit

Three situations eliminate the assessment statute entirely under IRC § 6501(c):

Fraudulent return. If a return was filed with the intent to evade tax, the IRS can assess at any time. No deadline. This is the provision most relevant to individual income tax disputes.

No return filed. If you never filed a return, the clock never starts. The IRS can assess at any time. Filing a substitute for return (SFR) under IRC § 6020(b) does not start the clock—only a return you voluntarily file does. This is one of the strongest reasons to file all delinquent returns: filing starts the 3 years clock.

A Warning About Preparer Fraud

In Murrin v. Commissioner, T.C. Memo. 2024-10, affirmed by the Third Circuit (No. 24-2037, Aug. 18, 2025), the court held that a tax preparer's fraudulent intent—not the taxpayer's own intent—is enough to trigger the unlimited assessment period. The taxpayer had no knowledge of the fraud, but the preparer added fictitious entries to the returns. The IRS assessed deficiencies more than 20 years later.

The Third Circuit relied on the statute's passive voice: it asks whether the return is fraudulent, not who made it fraudulent. A cert petition is pending before the Supreme Court as of early 2026, and the Federal Circuit has reached the opposite conclusion in BASR Partnership v. United States, 795 F.3d 1338 (Fed. Cir. 2015). The law may change, but for now, this risk is real in Third Circuit states (Pennsylvania, New Jersey, Delaware).

The takeaway: review your returns before signing them. Keep copies of everything.

When the IRS Asks You To Extend: Forms 872 and 872-A

During an IRS audit, the examiner may ask you to sign a consent form extending the assessment period. This happens because the IRS needs more time to complete the examination before the statute expires. You are not required to sign—and the law requires the IRS to tell you that.

Your Three Rights

Under IRC § 6501(c)(4)(B), every time the IRS requests a consent, it must notify you of three rights:

1. The right to refuse to extend
2. The right to limit the extension to specific issues (a restricted consent)
3. The right to limit the extension to a specific period of time

These rights come directly from the statute and are confirmed in IRS Publication 1035. No penalty may be imposed for refusing to sign.

Form 872 vs. Form 872-A

The IRS uses two forms. They work very differently.

Form 872 sets a specific expiration date—for example, December 31, 2027. When that date arrives, the extended assessment period ends. Form 872-A extends the period indefinitely until someone actively terminates it by filing Form 872-T. After the other party receives the termination notice, the statute expires 90 days later.

The open-ended consent is the riskier choice. If you sign Form 872-A and forget to file Form 872-T, the assessment period stays open for years—possibly decades. There is no urgency for the IRS examiner to finish the audit. If you have a choice, a fixed-date consent gives you far more control.

Restricted Consents

You can request that the consent be limited to specific issues—for example, only charitable contribution deductions or only Schedule C income. Publication 1035 confirms this right. The IRS will generally agree to restricted consents when the number of unresolved issues is manageable and the scope is clearly described, though an appropriate IRS official and IRS Counsel must approve the language.

What Happens If You Refuse To Sign

Per Publication 1035, refusing to extend means:

• The IRS will issue a Notice of Deficiency (90-day letter) to protect its assessment rights before the statute expires
• You have 90 days (150 days if abroad) to petition Tax Court
• The examiner must base the determination on whatever information has been provided to date
• You may lose the opportunity for an IRS Appeals conference if insufficient time remains on the statute

This is a genuine trade-off. Extending the statute gives the IRS more time—but it also gives you more time to gather documentation, present your case, and access Appeals. Refusing forces a faster decision, but that decision may be less favorable because the examiner has less information. There is no universal right answer; it depends on your case.

The Hidden Benefit: Extended Refund Period

Here is something most taxpayers miss. Under IRC § 6511(c), extending the assessment statute also extends your period for filing a refund claim to 6 months after the extended assessment period expires. If you later discover you overpaid, you still have time to claim it. This can be a real benefit if the audit uncovers errors in your favor.

The Collection Statute: How Long the IRS Has To Collect

The General Rule: 10 years

Once the IRS assesses a tax liability, it has 10 years to collect it through levy, lien, or court proceedings. This deadline is the Collection Statute Expiration Date, or CSED. When the CSED passes, the debt becomes legally unenforceable—the IRS must release any liens and stop all collection activity. (IRC § 6502)

Each assessment has its own CSED. A single tax year can have multiple CSEDs if there were multiple assessments—the original filing, an audit adjustment, and a penalty assessment might each have different expiration dates.

Events That Suspend the Collection Clock

The CSED clock pauses during certain events, giving the IRS more time. The major suspension events are:

• Installment agreement requests
• Offers in compromise
• Bankruptcy
• CDP hearings
• Innocent spouse requests
• Living outside the U.S. for 6 or more continuous months
• Military service

This creates an important trade-off: every action that pauses IRS collection also pauses the CSED. You gain breathing room, but the IRS gains extra time to collect if the arrangement falls through. For the full list of tolling events and how each one works, see How To Resolve Your IRS Tax Debt.

Extension by Installment Agreement

Under IRC § 6502(a)(2), the CSED can be extended by written agreement—but since 1998, the IRS can only do this in connection with an installment agreement. The IRS cannot request a standalone CSED extension. This means entering into an installment agreement may give the IRS collection time beyond the original 10 years period.

What Happens When the CSED Expires

When the collection statute expires, the debt is gone. The IRS must:

• Stop all collection activity
• Release any federal tax liens
• Cease any levies or garnishments

The debt becomes legally unenforceable. If the IRS continues collection activity after the CSED has passed, respond in writing citing the expiration and requesting that any liens be released.

This is also why currently not collectible (CNC) status—where the IRS designates your account as temporarily uncollectable because you cannot pay—can be a strategic option. CNC does not toll the CSED, so the clock keeps running while collection activity stops. For more on CNC and other resolution options, see How To Resolve Your IRS Tax Debt.

The Refund Statute: How Long You Have To Claim Money Back

The General Rule: Later of 3 years or 2 years

Under IRC § 6511(a), you must file a refund claim within the later of:

• 3 years from the date the return was filed, or
• 2 years from the date the tax was paid

Miss this window, and you lose the right to a refund entirely—even if you clearly overpaid. To file a refund claim, use Form 1040-X (for income tax overpayments) or Form 843 (for penalty and interest refunds).

The Lookback Limitation: How Much You Can Actually Recover

Even a timely refund claim does not guarantee full recovery. IRC § 6511(b) limits the amount:

• Claim filed within 3 years of the return: Refund is limited to tax paid during the 3 years (plus any extension period) before the claim
• Claim filed after 3 years but within 2 years of payment: Refund is limited to tax paid during the 2 years before the claim

Here is how this works in practice (from IRS Publication 556): Suppose you filed your return on time and paid $5,000 in tax through withholding and estimated payments over the year, plus $200 when you filed. If you file an amended return within 3 years, you can recover the full amount paid within the lookback window.

But if you wait past the 3-year mark and file within 2 years of a later payment, you can only recover what you paid in those 2 years—potentially just a fraction of what you overpaid.

The difference between filing a few weeks earlier and a few weeks later can be thousands of dollars.

Special Extended Periods

Some situations give you more time to claim a refund:

• Bad debts and worthless securities: 7 years (IRC § 6511(d)(1))
• Net operating loss carryback: 3 years from the due date of the loss year return (IRC § 6511(d)(2))
• Foreign tax credits: 10 years (IRC § 6511(d)(3))
• Financial disability: The limitations period is tolled while you are unable to manage your financial affairs due to a physical or mental impairment lasting 12 or more months. Requires a physician's certification. Does not apply if someone else (spouse, guardian) was authorized to act during the disability period. (IRC § 6511(h); Publication 556)

The Refund Suit Deadline

If the IRS denies your refund claim, you have 2 years from the date of the denial notice to file suit in U.S. District Court or the Court of Federal Claims. If the IRS does not act within 6 months, you can proceed to file suit without waiting for formal denial. (IRC § 6532)

For more on how amended returns serve as refund claims and the pay-and-sue path, see How To File an Amended Return.

How Tax Court Proceedings Affect All Three Clocks

Filing a Tax Court petition has significant effects on the statute clocks. Here is what happens to each one.

Assessment Statute: Suspended

Under IRC § 6503(a), the assessment statute is suspended from the date the IRS mails the Notice of Deficiency until the Tax Court decision becomes final, plus 60 days. The IRS loses no assessment time while your case is pending. If the ASED had 6 months remaining when the Notice of Deficiency was mailed, the IRS still has those 6 months (plus 60 days) after the decision becomes final.

For details on when Tax Court decisions become final and the post-decision assessment window, see What Happens After Your Tax Court Decision.

Collection Statute: Suspended

Collection is also suspended during Tax Court proceedings. The IRS is prohibited from assessing or collecting the deficiency while the case is pending under IRC § 6213(a). For a detailed explanation of this protection, see How IRC § 6213 Protects You While Your Tax Court Case Is Pending.

Refund Statute: Limited by IRC 6512(b)

If the Tax Court determines you overpaid your tax, your refund is governed by IRC § 6512(b)—not the normal refund statute rules. The Tax Court can only order a refund of amounts paid within the lookback period tied to the date the Notice of Deficiency was mailed. This means the timing of the Notice of Deficiency directly affects how much you can recover, even if the Tax Court finds entirely in your favor.

Interest: Not Suspended

Interest on the deficiency is not suspended during Tax Court proceedings. It continues to accrue from the original due date of the return. Because Tax Court cases typically takes 6-18 months to resolve, the interest can add up significantly. For more on how interest works, including the 36-month suspension rule under IRC § 6404(g), see How Interest Works on Your IRS Tax Debt.

Suspension Summary Table

How To Check Your Own Statute Dates

Finding Your ASED

For most taxpayers, the ASED is straightforward:

1. Find your filing date on your account transcript—look for the "return received" transaction
2. Compare it to your return due date (usually April 15, or October 15 if you had an extension)
3. Add 3 years to whichever date is later
4. Adjust for any consent forms you signed (Form 872 sets a specific date; Form 872-A means it is open until Form 872-T is filed plus 90 days)

Finding Your CSED

1. Find your assessment date on your account transcript—Transaction Code 150 for an original assessment, TC 300 for an additional assessment after an audit
2. Add 10 years
3. Adjust for any tolling events (installment agreements, OICs, bankruptcy, CDP hearings, and others listed above)

Here is the catch: taxpayer-accessible account transcripts show assessment dates but not the CSED itself. You have to calculate it, accounting for every tolling event. TXMODA transcripts—available only to practitioners with a power of attorney—show the actual computed CSED. For an explanation of the different transcript types and how to obtain them, see How To Get and Read Your IRS Transcripts.

Finding Your RSED

1. Find the date you filed the return
2. Add 3 years
3. Find the date you last made a payment for that tax year and add 2 years
4. The later date is your RSED

When You Need a Practitioner

If your case involves tolling events (past installment agreements, OIC applications, bankruptcy, CDP hearings), calculating the CSED yourself is difficult. Multiple overlapping suspensions can be hard to untangle. A practitioner with access to TXMODA can give you the actual date the IRS has on file.

If your income is below 250% of the poverty line and your dispute is $50,000 or less, a Low Income Taxpayer Clinic can help evaluate your statute dates at no cost. For guidance on other professional options, see When To Get Professional Help With Your Tax Dispute.

Common Mistakes To Avoid

Signing Form 872-A without understanding it. Many taxpayers sign whatever the examiner puts in front of them during an audit. An open-ended consent can leave the assessment period open for years. If possible, request Form 872 (fixed date) and negotiate a reasonable expiration date.

Assuming the 3 years rule always applies. If you omitted more than 25% of gross income, the IRS has 6 years. If a fraudulent return was filed—even by a preparer, under current Third Circuit law—the period is unlimited. If no return was filed, there is no deadline at all.

Not checking the actual CSED. The 10 years clock rarely runs clean. Past installment agreements, OIC applications, CDP hearings, and bankruptcy can all add months or years. Without checking TXMODA (through a practitioner), you may think a debt is about to expire when it actually has years left.

Filing refund claims too late. The 3 years/2 years deadline is absolute. Missing it by one day means losing the refund permanently. And even a timely claim can recover less than expected because of the lookback limitation.

Thinking an amended return restarts the assessment clock. Filing Form 1040-X does not give the IRS a new 3 years window. The original ASED continues to apply. (However, filing an amended return within 60 days of the ASED expiration gives the IRS an additional 60 days under IRC § 6501(c)(7).)

Not understanding that extending the assessment statute extends the refund period too. Signing a consent form extends your refund claim period to 6 months after the extended assessment period expires. This can actually benefit you if the audit reveals an overpayment.

Failing to file delinquent returns. If you never filed, the IRS has no assessment deadline—it can come after you at any time. Filing a return, even a late one, starts the 3 years clock.

Resources

Official IRS Resources

• IRS: Time IRS Can Assess Tax
• IRS: Time IRS Can Collect Tax
• IRS: Statutes of Limitations for Assessing, Collecting and Refunding Tax
• IRS Publication 1035—Extending the Tax Assessment Period
• IRS Publication 556—Examination of Returns, Appeal Rights, and Claims for Refund
• TAS: Assessment Statute Expiration Date (ASED)
• TAS: Understanding Your Collection Statute Expiration Date
• IRM 25.6.22—Extension of Assessment Statute of Limitations by Consent

Statutes

• IRC § 6501—Limitations on Assessment and Collection
• IRC § 6502—Collection After Assessment
• IRC § 6503—Suspension of Running of Period of Limitation
• IRC § 6511—Limitations on Credit or Refund
• IRC § 6532—Periods of Limitation on Suits
• IRC § 6404(g)—Suspension of Interest

IRS Forms

• Form 872—Consent to Extend the Time to Assess Tax (fixed-date)
• Form 872-A—Special Consent to Extend the Time to Assess Tax (open-ended)
• Form 872-T—Notice of Termination of Special Consent (terminates Form 872-A)
• Form 1040-X—Amended U.S. Individual Income Tax Return (refund claims for income tax overpayments)
• Form 843—Claim for Refund and Request for Abatement (refund claims for penalties and interest)
• Form 4506-T—Request for Transcript of Tax Return

Related Articles

• How To Resolve Your IRS Tax Debt—collection statute tolling events, installment agreements, OIC, and CNC strategy
• How To Get and Read Your IRS Transcripts—finding assessment dates and CSED on transcripts
• How To Respond to an IRS Audit—the audit process where Form 872/872-A is presented
• What To Expect at Your IRS Appeals Conference—how extending the statute preserves your Appeals opportunity
• You Just Got a 90-Day Letter From the IRS—the Notice of Deficiency that follows a refusal to extend
• How To File an Amended Return—amended returns as refund claims and the refund statute deadline
• How Interest Works on Your IRS Tax Debt—interest suspension under IRC § 6404(g)
• What Happens After Your Tax Court Decision—post-decision assessment suspension
• How IRC § 6213 Protects You While Your Tax Court Case Is Pending—collection protection during Tax Court
• Collection Due Process Hearings—CDP suspension of the collection statute
• How To Request Innocent Spouse Relief—innocent spouse filing deadlines and CSED tolling
• Tax Court vs. District Court vs. Court of Federal Claims—refund suit options under IRC § 6532
• How To Find and Use a Low Income Taxpayer Clinic—free help evaluating statute issues
• When To Get Professional Help With Your Tax Dispute—guidance on complex statute situations
• Common IRS Notices and Letters—understanding the notices that trigger these deadlines
• Understanding Your IRS Balance—how assessed liabilities appear on your account
• How To Request IRS Penalty Abatement—penalties follow the same assessment and collection statutes

This article is for informational purposes only and does not constitute legal or tax advice. For advice specific to your situation, consult a qualified tax professional or attorney.