A Notice of Deficiency—often called a 90-day letter—is the IRS’s formal determination that additional income tax, estate tax, gift tax, or certain penalties are owed. It generally permits a taxpayer to petition the United States Tax Court before paying the disputed amount.
The deadline is different from an ordinary response date
A petition generally must be filed within 90 days after the notice is mailed. The period is generally 150 days when the notice is addressed to a person outside the United States. The last date to petition is usually printed on the notice.
Tax Court jurisdiction is deadline-driven. Continuing to discuss the case with an IRS examiner or Appeals employee generally does not extend the petition deadline. The notice, envelope, mailing date, and online docket confirmation should be preserved.
Why Tax Court can matter
Tax Court is a prepayment forum: in a deficiency case, the taxpayer usually can contest the proposed tax before paying it. That differs from paying the tax, filing a refund claim, and later pursuing a refund suit in another federal court.
Immediate review points
- Confirm the notice is actually a statutory Notice of Deficiency.
- Identify each year, adjustment, penalty, and stated deficiency.
- Calendar the petition deadline independently and conservatively.
- Determine whether the correct taxpayer and address were used.
- Evaluate records, legal issues, burden-of-proof questions, and prior administrative opportunities.
- Decide whether to petition, concede, or pursue another permitted route.
Filing a petition begins litigation; it should not be confused with sending a protest letter to Appeals. The petition must meet the Tax Court’s rules, and later settlement discussions do not cure a missed filing deadline.