Background

When the IRS issues a Notice of Deficiency (often called a “90‑day letter”), it notifies a taxpayer of proposed adjustments and a proposed tax increase. The notice triggers a narrow window to go to Tax Court under Internal Revenue Code §6213 and related Tax Court rules (see IRS Publication 556 and the U.S. Tax Court’s procedures). Filing a petition lets you litigate the issue before the IRS can assess and collect the additional tax.

Key deadlines and who gets them

  • Standard deadline: 90 days from the date the IRS mails the notice (IRC §6213).
  • Overseas deadline: 150 days if the notice was mailed to an address outside the United States.
  • Miss the deadline and you generally lose the Tax Court option and must pursue other remedies after assessment (e.g., pay and sue for refund in U.S. District Court or Court of Federal Claims).

Required elements of a Tax Court petition

A valid petition must:

  1. Be filed with the U.S. Tax Court within the deadline.
  2. Include your name, current address, and the Tax Court docket designation information (tax year or period).
  3. State the amount in dispute and identify the specific adjustments you contest.
  4. Include a copy of the Notice of Deficiency (attach IRS notice).
  5. Be signed and include a certificate of service showing the IRS was served (see Tax Court Rules of Practice and Procedure).

How to file (practical steps)

  1. Read the notice carefully and confirm the mailing date. Check whether the notice lists the internal mailing date and whether it was delivered to a U.S. or foreign address.
  2. Decide whether you’ll file a regular Tax Court petition or seek small‑case (S‑case) procedures if eligible (small tax case threshold—see the U.S. Tax Court site). Small cases have simplified procedures but cannot create precedents.
  3. Draft the petition: keep allegations concise, state the legal and factual basis for your disagreement, and list relief requested.
  4. File on time: the Tax Court accepts paper petitions and maintains electronic filing procedures—confirm current filing methods and fees on the U.S. Tax Court website.
  5. Serve the IRS: follow Tax Court rules for service and include a Certificate of Service.
  6. Prepare to exchange documents and attend pretrial conferences; many cases settle before trial.

What to expect after filing

  • The Court will issue a notice of trial or preliminary conference.
  • Parties exchange pleadings and documents under the Court’s scheduling orders.
  • Many disputes settle through conferences or motions; a trial is an option if the parties disagree.

Common pitfalls and mistakes

  • Missing the 90‑day/150‑day deadline: this is the most consequential error.
  • Filing an incomplete petition (missing notice copy, unsigned petition, or no certificate of service).
  • Assuming Tax Court will grant extensions for late petitions—extensions are rarely available and the statutory deadline is strictly enforced.

Practical tips from practice

In my practice I’ve seen taxpayers gain leverage simply by filing timely and being organized. Commonly effective steps: gather tax returns, transcripts, third‑party statements (W‑2s, 1099s), and contemporaneous records before filing; state your core factual argument clearly in the petition; and consider retaining a tax attorney or CPA for complex fact patterns or large dollar exposures. Early settlement discussions under Tax Court procedures can reduce costs and time.

When a small‑case petition might help

If the disputed amount meets the Tax Court’s small tax case threshold, the streamlined S‑case process can reduce time and costs. Remember that S‑case decisions are not precedential and the relief available is the same in theory but procedurally simplified—review the U.S. Tax Court guidance before choosing that route.

Related resources (internal)

Authoritative sources and further reading

  • Internal Revenue Code §6213 (statutory right to petition Tax Court).
  • IRS Publication 556, Examination of Returns, Appeal Rights, and Claims for Refund (IRS).
  • U.S. Tax Court Rules of Practice and Procedure and the Court’s official website (U.S. Tax Court).

Common FAQs (short answers)

  • Do I have to pay before suing? No — filing a timely petition in Tax Court lets you contest the deficiency without paying the proposed tax first. (IRS Pub. 556)
  • Can I represent myself? Yes, but complex cases benefit from counsel.
  • What if the IRS corrected the issue after mailing the notice? You may still file and ask the Court to dismiss or enter judgment reflecting the corrected positions, but discuss options with counsel.

Limitations and disclaimer

This article is educational and does not provide legal or tax advice tailored to individual situations. Tax Court practice is procedural and fact specific; consult a qualified tax attorney or CPA for case‑specific guidance. The rules and thresholds referenced here are current as of 2025 but may change—always confirm with the IRS and U.S. Tax Court resources.