Deficiency jurisdiction

The deficiency case in one picture

Most Tax Court cases are deficiency cases, and the examination returns to them every time. The sequence is short:

1. The IRS examines a return and determines that more tax is due.
2. It mails a notice of deficiency (often called the "90-day letter") under IRC § 6212.
3. The taxpayer has 90 days (150 if the notice is addressed to a person outside the United States) to petition the Tax Court (IRC § 6213(a)).
4. Meanwhile the IRS may not assess or collect the deficiency; if a petition is filed, that bar lasts until the Court's decision becomes final (§ 6213(a); § 7481).
5. The IRS then assesses the amount the Court determines (§ 6215(a)).

Tax Court Rule 13(a) puts it in one sentence: in a case commenced by a taxpayer, the Court's jurisdiction depends on the Commissioner's issuing a notice of deficiency in income, gift or estate tax, certain excise taxes, or other taxes subject to a notice of deficiency.

What a "deficiency" is

A deficiency is not simply "the tax the IRS says you still owe". IRC § 6211(a) defines it as the amount by which the correct tax exceeds the tax shown on the return plus amounts previously assessed as a deficiency, minus rebates. Three refinements matter:

• Payments are ignored. Withholding (the § 31 credit) and estimated tax payments are disregarded on both sides of the computation (§ 6211(b)(1)). A taxpayer who overpaid through withholding can still have a deficiency.
• Refundable credits count as negative tax. Excess refundable credits (for example the earned income credit under § 32) are treated as negative amounts of tax (§ 6211(b)(4)), so disallowing a refundable credit can create a deficiency even when the tax before credits is zero.
• Which taxes. Deficiency procedures apply to income tax (subtitle A), estate and gift tax (subtitle B) and the chapter 41 to 44 excise taxes (§§ 6211(a), 6212(a)). They do not apply to employment taxes, and adjustments to partnership-related items are made only under the partnership rules (§ 6211(c)).

Worked example 1: computing deficiencies

Item	Taxpayer A	Taxpayer B
Correct tax as the IRS determines it	$26,900	$0 before credits; refundable credit disallowed
Tax shown on return	$18,400	$0 tax, $3,000 refundable credit claimed (negative tax of $3,000)
Previously assessed as a deficiency	$0	$0
Rebates	$0 (A's refund came from over-withholding, which § 6211(b)(1) ignores, so it is not a "rebate")	$0
Deficiency	$26,900 − $18,400 = $8,500	$0 − (−$3,000) = $3,000

The notice of deficiency: the taxpayer's "ticket" to the Court

Form and mailing. The IRS is authorized to send the notice by certified or registered mail, and the notice must tell the taxpayer of the right to contact the local Taxpayer Advocate office (IRC § 6212(a)).

Last known address. A notice mailed to the taxpayer's last known address is sufficient even if the taxpayer never receives it, is deceased or is under a disability (§ 6212(b)(1)). The regulation defines the last known address as the address on the most recently filed and properly processed return, unless the IRS has been given clear and concise notification of a different address; an address taken from the Postal Service's National Change of Address database can also become the last known address, but a change of address given only to some other third party does not (Treas. Reg. § 301.6212-2(a), (b)).

Joint returns. One joint notice may be sent for a joint return, but if either spouse has told the IRS they have established separate residences, a duplicate original must go to each spouse at his or her last known address (§ 6212(b)(2)).

The one-notice rule. If the taxpayer files a timely petition, the IRS may not determine an additional deficiency of income tax for the same year (or gift tax for the same calendar year, or estate tax for the same decedent), except for fraud, a math or clerical error, termination or jeopardy assessments, or by asserting an increased deficiency in the Tax Court case itself under § 6214(a) (§ 6212(c)(1)). The restriction is triggered by the petition. If the taxpayer lets a first notice lapse without petitioning, nothing in § 6212(c) stops the IRS from issuing a second notice for the same year; the first deficiency is assessed under § 6213(c), and a petition from the second notice puts only the second notice's determination before the Court.

Rescission. With the taxpayer's consent the IRS may rescind a notice; a rescinded notice is treated as never issued for purposes of the one-notice rule, the petition right and § 6512(a), though limitation periods stay suspended for the time it was outstanding (§ 6212(d)).

The 90-day (or 150-day) deadline

Section 6213(a) gives the taxpayer 90 days after the notice is mailed (150 days if the notice is addressed to a person outside the United States), "not counting Saturday, Sunday, or a legal holiday in the District of Columbia as the last day". Two further rules protect taxpayers:

• The date in the notice. If the notice specifies a last day to petition, a petition filed on or before that date is timely even if the IRS computed it too generously (§ 6213(a), last sentence).
• How filing is measured. A petition filed electronically through the Court's system is timely if filed by 11:59 p.m. eastern time on the last day (Tax Court Rule 22(d)). A mailed petition is treated as filed on the U.S. postmark date if it was properly addressed and postage was prepaid (IRC § 7502(a); Rule 22(c)); § 7502(f) extends this to private delivery services designated by the IRS.

Worked example 2: counting the days. The Court lists Emancipation Day in Washington, D.C. (April 16) as a legal holiday for computing time, even though the Court is open that day (U.S. Tax Court, Legal Holidays).

Notice mailed	Day 90	Last day to file
Friday, January 16, 2026	Thursday, April 16, 2026 (D.C. Emancipation Day)	Friday, April 17, 2026
Monday, July 6, 2026	Sunday, October 4, 2026	Monday, October 5, 2026
Monday, July 6, 2026, but the notice states "October 9, 2026" as the last day	Sunday, October 4, 2026	Friday, October 9, 2026, because the date stated in the notice controls when it is later

Is the deadline "jurisdictional"? Say exactly what is settled

This is an area of active change, so state the law carefully.

• Until 2024, Tax Court Rule 13(c) said that jurisdiction depended on a timely petition. Effective August 8, 2024, the Court deleted the text of Rule 13(c), explaining that, in light of Boechler, P.C. v. Commissioner, 596 U.S. 199 (2022) (the 30-day deadline for collection due process petitions is not jurisdictional), Myers v. Commissioner, 928 F.3d 1025 (D.C. Cir. 2019) (whistleblower petitions), and Culp v. Commissioner, 75 F.4th 196 (3d Cir. 2023) (deficiency petitions), it was no longer appropriate to address timing requirements in its Rules (Notice of Amendments, August 8, 2024).
• The courts of appeals are divided on § 6213(a). As described by the Sixth Circuit in Oquendo v. Commissioner, No. 24-1205 (6th Cir. Aug. 25, 2025), the Second, Third and Sixth Circuits hold that the deficiency deadline is not jurisdictional, so a late petition may in principle be saved by equitable tolling; the Seventh and Ninth Circuits, in decisions issued before Boechler, held that it is jurisdictional.
• The Tax Court itself held the deadline jurisdictional in Hallmark Research Collective v. Commissioner, 159 T.C. 126 (2022), and the Oquendo opinion shows the Court dismissing a late petition for lack of jurisdiction in 2024. Under the Golsen rule (previous lesson), the circuit to which an appeal would lie matters.
• Even where tolling is available, it is not automatic: the taxpayer must show circumstances that justify it (Oquendo).

For practice and for the examination, the safe statement is: file within the period; never rely on equitable tolling. If you discuss a late petition, explain the split and the role of the circuit of appeal, and say that later developments should be checked.

While the case is pending: the bar on assessment

Until the 90 days run, and if a petition is filed until the decision is final, the IRS may not assess the deficiency or levy or sue to collect it (§ 6213(a)). An assessment or levy made in violation may be enjoined, including by the Tax Court, and amounts collected may be ordered refunded, but the Tax Court has that power only if a timely petition has been filed and only for the deficiency that is the subject of the petition (§ 6213(a)).

The main exceptions:

Exception	Rule
Mathematical or clerical errors	The IRS may assess summarily; the notice is not a notice of deficiency. The taxpayer may request abatement within 60 days, after which the IRS must abate and use deficiency procedures to reassess (§ 6213(b)(1), (2)).
Payments	Any amount paid may be assessed when received; payment after the notice is mailed does not deprive the Court of jurisdiction (§ 6213(b)(4)).
Waiver	The taxpayer may waive the restrictions in a signed writing at any time (§ 6213(d)).
No petition	If no timely petition is filed, the deficiency is assessed and payable on notice and demand (§ 6213(c)).
Bankruptcy	The period to petition is suspended while the debtor is barred from filing, and for 60 days afterward (§ 6213(f)(1)).

What the Court may decide

• Increased deficiencies and penalties. The Court may redetermine a deficiency larger than the one in the notice, and additions to tax or penalties, if the Commissioner asserts the claim at or before the hearing (§ 6214(a)) (outside small tax cases: § 7463(c)).
• Other years. The Court considers facts from other years as needed to redetermine the year before it, but it has no jurisdiction to decide whether tax for another year was overpaid or underpaid; it may apply equitable recoupment to the same extent as the district courts and the Court of Federal Claims (§ 6214(b)).
• Overpayments. If the Court finds no deficiency, or a smaller one, and that the taxpayer overpaid tax for the same year, it determines the overpayment (§ 6512(b)(1)), subject to the look-back limits of § 6512(b)(3). If the IRS fails to refund a Court-determined overpayment within 120 days after the decision becomes final, the Court may order the refund on motion (§ 6512(b)(2)).
• Interest. Statutory interest is excluded from the deficiency procedures (§ 6601(e)(1)), so the Court generally does not redetermine interest in the deficiency case. The narrow exception: within one year after the decision becomes final, a taxpayer who paid the entire deficiency and interest assessed, and for whom the Court found an overpayment, may move to reopen the case solely to redetermine interest (§ 7481(c)).
• Transferees and fiduciaries. Liability of a transferee or fiduciary is assessed and contested like the underlying tax, after a notice of liability (IRC § 6901; Rule 13(a)).

Once you petition, you stay

A timely petition commits the year to the Tax Court:

• No refund suit may be brought for the same year, except for overpayments the Court determines and a few listed exceptions (§ 6512(a)).
• If the Court dismisses a deficiency case for any reason other than lack of jurisdiction, the dismissal is a decision that the deficiency is the amount the IRS determined (§ 7459(d)).

So a taxpayer who pays the deficiency after petitioning and then asks to dismiss the case in order to sue for a refund elsewhere gains nothing: payment does not divest the Court of jurisdiction (§ 6213(b)(4)); dismissal would enter a decision for the full deficiency (§ 7459(d)); and § 6512(a) would bar the refund suit. The reverse situation is governed by § 7422(e): if the IRS mails a notice of deficiency while a refund suit is pending, the suit is stayed, and if the taxpayer petitions the Tax Court, the refund court loses jurisdiction to the extent the Tax Court acquires it.

Finally, the decision in a regular case becomes final when the time to appeal expires without an appeal, or at the end of the appellate process (§ 7481(a)); a small tax case decision becomes final 90 days after it is entered (§ 7481(b)).

Common traps

• Subtracting withholding when computing a deficiency. Section 6211(b)(1) disregards it.
• Assuming the one-notice rule always applies. It is triggered only by a timely petition from the first notice.
• Forgetting that the 150-day period depends on where the notice is addressed, and that the date stated in the notice can extend (never shorten) the period.
• Treating D.C. Emancipation Day like an ordinary business day for the deadline.
• Saying payment after the notice ends the case. It does not (§ 6213(b)(4)).
• Overstating the jurisdiction question. Say what the Tax Court and each side of the circuit split hold.

How the examination tests this

Expect short fact patterns: a taxpayer who ignored one notice and petitioned a second, a petition mailed on the last day, a request to dismiss after paying, a petition that contests interest, or a question about what the Court may decide. The 2021, 2023 and 2025 examinations (on the Court's Guidance for Practitioners page) all include deficiency-procedure questions answered in a few sentences. Name the statute, apply it to each fact, and state the result.

Check yourself

• Compute the deficiency when the correct tax is $40,000, the return showed $31,000, $5,000 was previously assessed as a deficiency, and withholding was $45,000.
• A notice of deficiency is mailed on Monday, July 6, 2026. What is the last day to file a petition, and how late in that day may it be filed electronically?
• When may the IRS issue a second notice of deficiency for a year, and what limits the Court's jurisdiction in the second case?
• A taxpayer pays the full deficiency after petitioning and moves to dismiss to sue for a refund in district court. Explain the result under §§ 6213(b)(4), 7459(d) and 6512(a).
• Summarize the circuit split on whether the § 6213(a) deadline is jurisdictional and the Tax Court's position.
• When can the Tax Court redetermine interest, and under which section?