90-Day Letter

Last updated 29th Nov 2022


The term 90-day letter refers to a notice sent to taxpayers stating there was an error in their income tax return, and the amount owed will be assessed unless a petition is filed. A 90-day letter is issued when taxpayers fail to respond to, or protest, a 30-day letter. The letter is a legal document, and is typically sent to the taxpayer via certified or registered mail.


Also known as a Statutory Notice of Deficiency (SND), the Internal Revenue Service (IRS) has the authority under Section 6212(a) of the tax code to send a taxpayer a 90-day letter when it has determined through an audit a deficiency exists with respect to income, estate, or gift taxes.

The notice of deficiency presumes the audit finding is correct. The letter will explain the purpose of the notice, the amount owed, IRS contact information, and descriptions of the taxpayer's options. The letter will also indicate how the amount owed was calculated, including the assessments of penalties.

The taxpayer has 90 days to respond to the letter or the deficiency will automatically result in a reassessment of taxes owed. If the taxpayer does not agree with the finding, they need to file a petition with a Tax Court, asking for a redetermination of the deficiency. If the taxpayer fails to agree to the finding or file a petition, the IRS will take action to collect the amount owed.

Note: Taxpayers located outside of the United States have 150 days to respond to this letter.

Related Terms

30-day letter, tax bracket

Moneyzine Editor

Moneyzine Editor