90-day letter

A 90-day letter, also called a Notice of Deficiency, CP3219N Notice, or Letter 531, is a formal legal notice issued by the Internal Revenue Service (IRS) under 26 U.S.C. § 6212(a). The notice is sent when the IRS determines that a taxpayer has either failed to file a return or filed a return with a deficiency in tax owed. The IRS calculates the taxpayer’s liability using information reported by employers, financial institutions, and other third parties, and then issues the notice by certified or registered mail. The 90-day letter explains the IRS’s determination of tax, penalties, and interest, and informs the taxpayer of available options. Within 90 days of the mailing date (150 days if addressed outside the United States), the taxpayer may petition the United States Tax Court to contest the determination without first paying the tax. Alternatively, the taxpayer may pay the assessed amount and then file a refund claim, pursuing litigation in federal district court or the Court of Federal Claims if the refund is denied. Failure to act within the deadline forfeits the right to contest the IRS’s assessment.

[Last reviewed in September of 2025 by the Wex Definitions Team] 

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