A Notice of Deficiency (CP3219A), also called the “90-day letter” or Statutory Notice of Deficiency, is the IRS’s formal determination that you owe more tax. It is the legal ticket to U.S. Tax Court — the one place you can dispute the tax before paying it.
Deadline — strict, no extensions: you have 90 days from the date on the notice (150 days if it’s addressed outside the U.S.) to file a petition with the U.S. Tax Court. Miss it and the tax is assessed and becomes collectible — you lose the pre-payment challenge. This deadline cannot be extended for any reason.
Your two paths
- You disagree → petition the Tax Court by the 90-day deadline. You can file online at the Tax Court’s website (ustaxcourt.gov) with the petition form and the filing fee; filing suspends assessment while the case is pending. You can still try to resolve it with the IRS in parallel.
- You agree → sign and return the enclosed Form 5564 (waiver) and pay or set up a plan.
If new documents would change the IRS’s mind, send them too (letter below) — but do not let that replace filing the Tax Court petition if the deadline is near, because only the petition preserves your rights.
The letter (sending documents to the IRS in parallel)
[Your name]
[Address]
[City, State ZIP]
[Daytime phone]
[Date]
Internal Revenue Service
[Use the address on the CP3219A notice]
Re: CP3219A Notice of Deficiency - response and supporting documents
Name: [Your name] SSN/ITIN: [xxx-xx-1234]
Tax year / form: [year / 1040]
Notice date: [date] 90-day deadline: [date + 90 days]
To whom it may concern:
I disagree with the deficiency proposed for [year]. The following supporting
documents show the proposed change is incorrect:
- [Item]: [explanation], see attached [document].
- [Item]: [explanation], see attached [document].
Please reconsider the proposed deficiency based on this information. To protect my
rights, I am also filing (or have filed) a timely petition with the United States
Tax Court within the 90-day period.
Sincerely,
[Signature]
[Printed name]
How to send it / file
Calendar the 90-day date the moment the notice arrives. To preserve your rights, file the Tax Court petition by that date (ustaxcourt.gov) — this is the safe move even if you’re also negotiating with the IRS. Send any documents to the IRS by certified mail with return receipt, and keep copies of everything.
Notes. This is the highest-stakes IRS notice — the 90-day deadline is jurisdictional and truly final, so strongly consider a tax attorney, CPA, or enrolled agent, or a free Low Income Taxpayer Clinic, immediately. A Notice of Deficiency usually follows an ignored CP2000 or audit. General information, not legal or tax advice — confirm everything at irs.gov and ustaxcourt.gov.