Understanding IRS statutes of limitations

The IRS statutes of limitations are among the most important deadlines that tax professionals track, yet they are often misunderstood. Whether dealing with audits, collections or refund claims, understanding which deadline applies can help practitioners protect clients and avoid costly mistakes.

The IRS generally operates under three separate statutes of limitations:

• Assessment statutes 
• Collection statutes 
• Refund statutes 

Each serves a different purpose and follows different rules.

The assessment statute

The assessment statute determines how long the IRS has to examine a return and assess additional tax. In most situations, the IRS has three years from the later of:

• The return due date 
• The date the return was filed 

For example, assume a taxpayer files a 2024 individual return on March 1, 2025. Even though the return was filed early, the three-year statute begins on the original due date of April 15, 2025. In that situation, the IRS generally has until April 15, 2028, to assess additional tax.

If the taxpayer files late, the statute begins on the actual filing date.

When the assessment statute extends

If a taxpayer substantially understates income, the IRS may receive additional time. Generally, the statute extends to six years if the taxpayer omits more than 25% of gross income reported on the return.

Example:

A taxpayer reports $200,000 of gross income but omits $60,000 of the gross income. Because the omitted amount exceeds 25% of the reported income, the IRS may have six years instead of three to assess additional tax.

Foreign income reporting issues may also trigger longer statutes in certain situations.

Situations with no assessment statute

In some cases, the statute never expires.

The IRS may assess tax at any time if:

• No return was filed 
• A fraudulent return was filed 
• The taxpayer willfully attempted to evade tax 

Under §6501(c), the statute is unlimited in two primary situations: (1) a false or fraudulent return filed with intent to evade tax under §6501(c)(1), and (2) willful attempt to defeat or evade tax under §6501(c)(2). No return filed falls under §6501(c)(3). For tax professionals, this is an important reminder that failing to file does not start the clock. The statute begins only after a valid return is filed.

The collection statute

Once tax is assessed, a separate statute begins. The IRS generally has 10 years from the assessment date to collect the liability. This deadline is commonly called the Collection Statute Expiration Date (CSED).

This is one area where practitioners often see confusion. The 10-year period does not begin when the return is filed or when the tax year ends. It begins when the IRS officially assesses liability.

Example:

A taxpayer files a balance-due return in 2025, and the IRS assesses the tax on June 1, 2025. The IRS generally has until June 1, 2035, to collect the balance. After the CSED expires, the IRS can no longer legally pursue collection activity for that liability.

Events that pause the collection statute

Certain taxpayer actions suspend, or toll, the collection statute. During those periods, the clock temporarily stops running.

Common tolling events include:

• Filing an offer in compromise (OIC)
• Bankruptcy proceedings 
• Collection Due Process hearings 
• Certain periods spent outside the United States 

Example:

A taxpayer submits an OIC that remains pending for eight months. The IRS may add those eight months, plus additional statutory time, to the original CSED. For practitioners handling collection cases, tracking tolling periods is critical because the actual expiration date may be much later than the original 10-year deadline.

The refund statute

The statute also works in the taxpayer’s favor. Generally, taxpayers must file a refund claim within:

• Three years from the date the return was filed 
• Two years from the date the tax was paid, whichever is later 

Example:

A taxpayer files a 2022 return on April 15, 2023, but later discovers an overlooked deduction. The taxpayer generally has until April 15, 2026, to file an amended return claiming a refund.

If the deadline passes, the refund may be permanently lost.

This issue commonly arises when taxpayers delay filing amended returns or fail to reconcile estimated tax payments, carrybacks or refundable credits in time.

Statute tracking 

Statutes of limitations affect nearly every stage of tax controversy work. Missing a deadline can eliminate refund opportunities or extend IRS exposure. Accurate statute tracking helps:

• Identify audit exposure 
• Evaluate collection options 
• Protect refund claims 
• Improve record retention guidance 
• Manage client expectations 

The key takeaway is simple: IRS statutes of limitations are not one-size-fits-all. Assessment, collection and refund statutes all operate independently, and exceptions can significantly alter the timeline.