Unpacking the IRS CP3219N Notice: A Taxpayer's Guide to the 90-Day Letter and US Tax Court
- Howard Richardson
- Dec 22, 2025
- 6 min read
Receiving a notice from the Internal Revenue Service (IRS) can be a stressful experience for any taxpayer. Among the various notices the IRS sends, the CP3219N, also known as the Statutory Notice of Deficiency or the "90-day letter," is one of the most critical. This notice is a legal determination by the IRS that you owe additional taxes, and it starts a strict 90-day countdown for you to take action.
What is a Notice of Deficiency?
A Notice of Deficiency is a legal notice in which the Commissioner of the IRS determines a taxpayer's tax deficiency. It is a formal assertion that you owe more taxes than what you reported on your return, or that you owe taxes because you did not file a return at all. The notice is not a bill; rather, it is a proposal of additional tax liability. Its primary purpose is to inform you of the IRS' proposed changes and to give you an opportunity to challenge them in the United States Tax Court before the tax is assessed and you have to pay it.
A Notice of Deficiency consists of several components:
•A letter explaining the purpose of the notice, the amount of the deficiency, and your options.
•A waiver form (Form 4089) that allows you to agree to the additional tax liability.
•A statement showing how the deficiency was computed.
•An explanation of the adjustments made by the IRS.
Why Did I Receive a CP3219N Notice?
The most common reason for receiving a CP3219N notice is that the IRS believes you have unreported income. The IRS' Automated Underreporter (AUR) program matches information returns from third parties, such as Form W-2 from your employer and Form 1099 from financial institutions, with the income you reported on your tax return. If there is a discrepancy, and you have not responded to previous notices about it, the IRS will issue a CP3219N notice.
Another common reason for receiving a CP3219N is when you have not filed a tax return at all. In this case, the IRS will create a Substitute for Return (SFR) based on the income information it has received from third parties. The SFR will calculate the tax you owe, but it will not include any deductions or credits you may be entitled to. The CP3219N notice will then be sent to inform you of the proposed tax liability based on the SFR.
A Notice of Deficiency must be issued when there is a proposed tax deficiency that the taxpayer does not agree with, and:
•The statute of limitations for assessing the tax is about to expire.
•The taxpayer does not respond to a 30-day letter (a preliminary notice proposing changes to the tax return).
•The taxpayer requests the issuance of the notice in order to petition the US Tax Court.
The Legal Authority Behind the CP3219N Notice
The IRS' authority to issue a Notice of Deficiency is granted by the Internal Revenue Code (IRC). Specifically, IRC § 6212 authorizes the Secretary of the Treasury to send a notice of deficiency to a taxpayer by certified or registered mail if a deficiency is determined. The notice must be sent to the taxpayer's "last known address," a term that is further defined in Treasury Regulations and has been the subject of much litigation.
IRC § 6213 provides the taxpayer with the right to challenge the deficiency in the US Tax Court. This section states that a taxpayer has 90 days (or 150 days if the notice is addressed to a person outside the United States) after the notice of deficiency is mailed to file a petition with the US Tax Court for a redetermination of the deficiency. This 90-day period is critical, as failure to file a petition within this timeframe will result in the assessment of the tax, and the taxpayer will lose the right to challenge the deficiency in Tax Court before paying it.
Your Options After Receiving a CP3219N Notice
Upon receiving a CP3219N notice, you have three main options:
1. Agree with the notice: If you agree with the proposed changes, you can sign the enclosed Form 4089, "Waiver of Restrictions on Assessment and Collection of Deficiency in Tax and Acceptance of Overassessment." By signing the waiver, you are agreeing to the assessment of the tax, and the IRS can begin the collection process. You will still have the right to file a claim for a refund after you pay the tax.
2. Disagree with the notice and file a tax return: If you have not filed a tax return, the CP3219N notice is based on an SFR that does not include any of your eligible deductions or credits. By filing a correct tax return, you can significantly reduce or even eliminate the proposed tax liability. The IRS will then reassess your tax liability based on your filed return.
3. Disagree with the notice and file a petition with the US Tax Court: If you disagree with the proposed deficiency, you can file a petition with the US Tax Court within the 90-day period. This is your opportunity to have a judge review your case before you have to pay the disputed amount. It is highly recommended that you seek the assistance of a qualified tax professional if you choose this option.
The 90-Day Deadline and Filing a Tax Court Petition
The 90-day deadline for filing a petition with the US Tax Court is absolute and cannot be extended. The 90-day period begins on the date the CP3219N notice is mailed, not the date you receive it. If the 90th day falls on a Saturday, Sunday, or legal holiday in the District of Columbia, the deadline is extended to the next business day.
Filing a petition with the US Tax Court is a formal legal process. The petition must be in writing and must include a copy of the CP3219N notice. The US Tax Court has a simplified procedure for small tax cases, where the amount in dispute is $50,000 or less for any one tax year. This procedure is less formal and can be less expensive than the regular US Tax Court procedure.
What Happens If You Do Nothing?
If you do not respond to the CP3219N notice within the 90-day period, the IRS will assess the proposed tax, plus any penalties and interest. You will then receive a bill for the amount due. At this point, you will have lost your right to challenge the deficiency in US Tax Court before paying it. Your only recourse will be to pay the tax and then file a claim for a refund. If the claim for refund is denied, you can then sue for a refund in a US District Court or the US Court of Federal Claims.
The Importance of the "Last Known Address"
The validity of a CP3219N notice hinges on whether it was mailed to your "last known address." Treasury Regulation § 301.6212-2 defines the last known address as the address that appears on your most recently filed and properly processed tax return, unless the IRS is given clear and concise notification of a different address. Revenue Procedure 2010-16 provides guidance on how to provide the IRS with a clear and concise notification of a change of address.
If the IRS does not send the notice to your last known address, the notice may be invalid. This could be a powerful defense if you did not receive the notice and the 90-day period has expired. However, the burden of proof is on the taxpayer to show that the IRS did not exercise reasonable care and diligence in determining the last known address.
Conclusion
The IRS CP3219N notice is a serious matter that requires your immediate attention. It is a legal document that starts a 90-day clock for you to take action. Understanding your rights and options is crucial to achieving a favorable outcome. Whether you agree with the notice, disagree and want to file a return, or wish to challenge the deficiency in US Tax Court, it is highly recommended that you consult with a qualified tax professional to guide you through the process.
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