Quick overview

The statute of limitations for tax assessments and refund claims sets deadlines both the IRS and taxpayers must meet. For most individual income tax returns, the IRS has three years from the date the return was filed to assess additional tax. For taxpayers seeking a refund, the deadline to file a claim for credit or refund is the later of (a) three years from the date the return was filed, or (b) two years from the date the tax was paid (26 U.S.C. § 6511; see IRS Publication 556). There are critical exceptions — notably fraud, no return filed, or substantial omission of income — that either extend or remove these limits.

(Authoritative sources: IRS Pub. 556 and IRS guidance on statute of limitations: https://www.irs.gov/publications/p556 and https://www.irs.gov/newsroom/statute-of-limitations.)

How the standard deadlines work (plain language)

  • IRS assessment window: Generally three years from the date you filed your return. That means if you file early or late, the three-year clock starts on the date the return was filed (or the due date if an extension applies in some contexts). The IRS can open an audit and assess additional tax during this window.

  • Taxpayer refund window: To claim a refund (including filing an amended return via Form 1040-X), you must file a claim by the later of:

  • three years from the date the original return was filed, or

  • two years from the date you paid the tax.

This “later of” rule is important: a payment made long after the return was filed can extend your refund window.

(See IRS Pub. 556 and 26 U.S.C. § 6511 for the statutory text and examples.)

Common exceptions and special rules

  • Substantial omission of income (six-year rule): If you omit more than 25% of your gross income on a return, the IRS generally has six years to assess additional tax instead of three (IRS guidance and tax code). This most often applies when a taxpayer fails to report a significant source of income.

  • Fraud or no return filed: There is no statute of limitations if the return was false due to fraud or if no return was filed. The IRS can assess tax at any time in these situations.

  • Signed consent/waivers: Taxpayers can sometimes sign a consent agreement to extend audit timeframes (for example, during an audit when more time is needed). An extension in writing pauses the normal deadline until the extension period ends.

  • Refunds after audit adjustments: If the IRS adjusts your return and you believe you’re due a refund, different timing and processes may apply. See our guide on filing a claim for refund after an audit adjustment for practical steps and timing implications: How to File a Claim for Refund After an Audit Adjustment.

  • Special rules for business, payroll, estate, and foreign income: Certain business or trust returns and employment taxes can have different timelines; foreign-earned income and certain foreign filing omissions have expanded lookback periods. Always check the specific rules for the tax type involved.

Practical date examples

Example 1 — Typical individual return

  • Return filed: April 15, 2022
  • IRS deadline to assess: April 15, 2025 (three years)
  • Refund claim deadline: later of April 15, 2025 or two years after date of tax payment. If you paid additional tax on May 1, 2022, the refund deadline could be May 1, 2024 — but because April 15, 2025 is later, that is the applicable limit.

Example 2 — Payment made after filing

  • Return filed: April 15, 2020
  • Tax paid: January 1, 2021 (e.g., estimated tax paid later)
  • Refund claim deadline: later of April 15, 2023 (three years from filing) or January 1, 2023 (two years from payment) → April 15, 2023 applies.

Example 3 — Substantial omission (6-year rule)

  • Return filed: April 15, 2018
  • IRS can assess through April 15, 2024 if the omission of income exceeds 25% of gross income.

These examples show why tracking both filing and payment dates matters.

Recordkeeping: how long should you keep tax records?

The IRS’s advice varies by situation, but practical guidance most tax professionals follow is:

  • Keep records for at least 3 years from the date you filed your original return (or 2 years from the date the tax was paid, whichever is later), because this covers the normal refund and assessment windows.
  • Keep records for 6 years if you omitted more than 25% of your gross income in a year.
  • Keep records indefinitely if you didn’t file a return or if fraud is suspected.
  • Keep records for 7 years for claims involving bad debt or worthless securities and for other specific tax issues.

For a full checklist on what to keep and typical retention periods, see our detailed recordkeeping guide: Recordkeeping Requirements: What the IRS Expects and How Long to Keep Records, and consult the IRS page “How long should I keep records?” (https://www.irs.gov/individuals/how-long-should-i-keep-records).

Common mistakes I see in practice

  • Assuming “filed” and “paid” dates are the same: Payments can occur after filing (estimated tax, amended payments) and that can alter the refund deadline.

  • Throwing away records after three years: In cases of substantial underreporting, keeping six years or more of documentation matters.

  • Missing consent or waiver details: Taxpayers sometimes sign waivers without understanding they’re extending the audit window.

  • Not monitoring refund offsets: Refunds can be reduced or taken by the Treasury Offset Program to satisfy past-due federal or state debts. If you expect a refund, check offsets early — see our article on offsets: Understanding Refund Offsets for Past-Due Federal Debts.

Steps to protect your rights (checklist)

  1. Confirm the filing and payment dates on your tax return and bank/IRS payment records.
  2. If you believe you’re due a refund, file a timely claim — most refund claims follow the same deadline rules and are submitted via Form 1040-X for individual returns.
  3. Keep supporting documentation for at least the length of the applicable statute of limitations (3–6 years in most cases; longer if issues exist).
  4. If audited, read the IRS notice carefully, meet deadlines, and consider professional representation if complexity or large amounts are at stake.
  5. If a refund is offset or reduced, review the notice and follow the appeal or dispute instructions promptly.

When to consult a tax professional

If you face any of these situations, get professional help:

  • The IRS notifies you after the standard 3-year period and cites fraud or a substantial omission.
  • You think a refund claim is close to or past the deadline and you have proof of payment or filing dates.
  • Your refund was offset and you believe the offset is incorrect.
  • You are asked to sign a waiver or extension during an audit.

In my practice, timely documentation and conservative retention policies prevent most surprises. A short conversation with a CPA or tax attorney can often clarify whether a claim is timely and preserve your rights to a refund.

Disclaimer:
This article is educational and does not constitute tax advice for your specific situation. For definitive answers, consult the IRS resources cited above and a qualified tax professional. Official IRS guidance includes Publication 556 and the statute at 26 U.S.C. § 6511 (see https://www.irs.gov/publications/p556).

Relevant resources and internal guides:

Authoritative sources:

Author: FinHelp.io editorial — tax content reviewed for accuracy as of 2025.