The notice of deficiency (90-day letter): what it is, how it is mailed and how the Tax Court clock runs

What a notice of deficiency is

IRM 4.8.9.2 calls the notice of deficiency (also the statutory notice or 90-day letter) a legal notice in which the Commissioner determines the deficiency, adding that it “is a legal determination that is presumptively correct”. IRC 6212 and 6213 require it before the IRS assesses additional income, estate, gift, generation-skipping transfer and certain excise taxes, unless the taxpayer agrees. It has four parts: a letter explaining the notice, the deficiency and the options; a waiver the taxpayer can sign to agree; a statement of how the deficiency was computed; and an explanation of the adjustments. IRC 6212(a) also requires it to tell the taxpayer of the right to contact the local Taxpayer Advocate office.

Field cases use Letter 531 (with Letter 902 and other variants); campus correspondence cases use Letter 3219 (see also CP3219A).

When the IRS issues one

Under IRM 4.8.9.3, a notice must be issued when there is a proposed deficiency the taxpayer does not agree with and one of three things is true: the statute is imminent and no extension can be obtained; the taxpayer does not respond to, or file a valid protest to, a 30-day letter; or the taxpayer asks for the notice so they can petition. That last ground is useful: a taxpayer who prefers the Tax Court to Appeals, or who will not extend the statute, can ask for the notice instead of waiting.

If a 30-day letter was issued, the notice should go out within 60 days after Technical Services receives the case, or sooner if the statute is close (IRM 4.8.9.4). In campus cases it follows the 30-day letter's suspense period (see correspondence examinations).

What makes the notice valid

Last known address

IRC 6212(b)(1) makes a notice mailed to the taxpayer's last known address sufficient, even if the taxpayer has died, is under a disability or, for a corporation, has ceased to exist (absent a fiduciary notice under IRC 6903). Treas. Reg. 301.6212-2(a) defines the last known address as the address on the most recently filed and properly processed return, unless the taxpayer has given clear and concise notice of a change, with updates from the Postal Service's National Change of Address database (IRM 4.8.9.9.2.1). If there is doubt, the IRS sends duplicate original notices to each possible address.

IRM 4.8.9.9.2.2 explains what counts as notice of a new address: a signed statement with full name, old and new address and TIN, Form 8822, or a reply to IRS correspondence returned with a corrected address. The IRM then lists what does not count: a new address on letterhead, a return envelope or a remittance form, a post office notice outside the NCOA database, or the filing of Form 2848 or Form 4868. A client who moved and only told you, or only put the new address on a Form 2848, has not updated the IRS.

Certified or registered mail

The notice must go by certified or registered mail. IRM 4.8.9.12.4 warns that “A notice may be determined to be invalid if it is not mailed to the last known address or if it is not mailed by certified or registered mail, as required.” The IRS proves mailing with PS Form 3877, the certified mail list signed and postmarked by the Postal Service, which it keeps for 10 years (IRM 4.8.9.12.3); the Commissioner has the burden of proving the mailing date. When challenging a notice, ask for the Form 3877.

The representative's copy

A representative receives a copy by regular mail with Letter 937 if the Form 2848 is annotated to receive copies. If the power of attorney does not cover every year in the notice, no copy is sent to the representative; the taxpayer's notice includes Letter 4368 explaining why (IRM 4.8.9.12.2). The representative's copy is a courtesy: the period runs from the mailing to the taxpayer. Check the years on the 2848 against the exam years before the case reaches Technical Services.

Challenging the notice itself

When the petition period has passed, the one argument that can still reach the Tax Court is that the notice was never valid, which usually means it was not sent to the last known address. The rules are in Treas. Reg. 301.6212-2 and Rev. Proc. 2010-16, which explains how the IRS determines the address of record: the address on the most recently filed and properly processed return controls unless the taxpayer gave clear and concise notification of a change, and the IRS also updates addresses from the Postal Service's NCOA database. Rev. Proc. 2010-16, section 5.04 defines clear and concise notification as a signed written statement with the full name, old and new address and TIN, IRS correspondence returned with corrected address information, Form 8822, or an address change through a secure IRS online application; it says that a new address in the letterhead of taxpayer correspondence does not by itself change the address of record, and that email to an IRS address does not qualify.

The rule is the Tax Court's as well as the IRS's. In Abeles v. Commissioner, 91 T.C. 1019 (1988), the court held that “a taxpayer's last known address is that address which appears on the taxpayer's most recently filed return, unless respondent has been given clear and concise notification of a different address,” and that the most recently filed return is one that has been properly processed so that its address was available to the agent issuing the notice. Abeles also held that when the IRS has been told that joint filers live at separate addresses it must send duplicate originals of the joint notice to each spouse's last known address; because the notice there went only to the husband's address, it was invalid as to the wife and her case was dismissed for lack of jurisdiction. Treas. Reg. 301.6212-2 and Rev. Proc. 2010-16 adopt the Abeles rule, so the argument succeeds only where a later processed return or a qualifying change notice preceded the mailing.

A rarer attack is that no determination was made at all. In Scar v. Commissioner, 814 F.2d 1363 (9th Cir. 1987), the notice disallowed a loss from a tax shelter the taxpayers had never invested in and, stating that their return was unavailable, computed tax at the maximum rate; the Ninth Circuit held that because the notice “revealed on its face that no determination of tax deficiency had been made” it did not satisfy IRC 6212(a), and the Tax Court should have dismissed for want of jurisdiction. The court repeated that no particular form is required and the IRS need not explain its computation, so Scar reaches only a notice that shows on its face that it is not about the taxpayer's own return; a notice that is merely wrong is valid, and the remedy is to litigate the deficiency in the Tax Court.

The flip side matters more often. IRC 6212(b)(1) says a notice mailed to the last known address “shall be sufficient” even if the taxpayer has died, is under a legal disability or, for a corporation, has ceased to exist. The statute keys validity to mailing, not receipt: a notice properly mailed by certified or registered mail to the last known address starts the 90 days whether or not the client ever opened it, and a client who moved without telling the IRS has no address defense. The practitioner's checklist is therefore: get the PS Form 3877 (IRM 4.8.9.12.3), compare the address on it with the address on the last processed return and any Form 8822 or returned correspondence, and check whether an NCOA update posted (shown as a TC 014). If the notice went to a stale address after the IRS had clear and concise notification of the new one, IRM 4.8.9.12.4 says the notice may be invalid; if the ASED has since passed, any assessment based on it “cannot be made and, if already made, must be abated”. If the notice is invalid but the statute is still open, the win is temporary: the IRS issues a new notice to the correct address and the clock starts again.

The dates on the notice

The notice carries two dates: the date issued (the mailing date) and the last day to petition the Tax Court (IRM 4.8.9.11.2). IRC 6213(a) sets the period at 90 days after mailing, or 150 days if the notice is addressed to a person outside the United States, and the last day cannot fall on a Saturday, Sunday or District of Columbia legal holiday. The printed date protects the taxpayer: “Any petition filed with the Tax Court on or before the last date specified for filing such petition by the Secretary in the notice of deficiency shall be treated as timely filed.” If the IRS knew the taxpayer was abroad but mailed to a U.S. address, the IRM tells reviewers to coordinate with Counsel on the proper period. How to file and the small case option are in Tax Court petitions and the small tax case procedure, which under IRC 7463 is available when the amount in dispute for a year is $50,000 or less.

Filing on time: mail, DAWSON and the late petition

Mailing. IRC 7502(a) applies to a Tax Court petition: if it is delivered by U.S. mail after the deadline, the postmark date is deemed the delivery date, provided the postmark is within the period and the petition was deposited in the mail, postage prepaid and properly addressed to the Tax Court. IRC 7502(c)(1) makes registration prima facie evidence of delivery and treats the registration date as the postmark date; 7502(c)(2) authorizes regulations extending that treatment to certified mail and electronic filing, and 7502(f) treats designated private delivery services as U.S. mail. IRM 4.8.9.27.1 warns of the trap: a petition mailed to the IRS office that issued the notice is not properly addressed, so it counts only if the Tax Court receives it by the 90th day; Technical Services forwards an early-arriving petition but returns one that arrives after the period with Letter 4372.

Electronic filing. Petitions filed through the Tax Court's DAWSON system are governed by Tax Court Rule 22(d): a paper “will be considered timely filed if it is electronically filed at or before 11:59 p.m., eastern time, on the last day of the applicable period for filing.” The timestamp is Eastern time regardless of where the petitioner is. Rule 22(c) points mailed petitions back to IRC 7502. Our Tax Court petition deadline calculator computes the last day from the mailing date, including the weekend and holiday rule.

The only extensions. Nothing in IRC 6213 allows the IRS or the court to extend the period, and the IRS says so in every post-notice letter. Two statutes outside 6213 can move it. IRC 7508(a)(1)(C) disregards the time an individual serves in a combat zone or contingency operation (plus 180 days) for “Filing a petition with the Tax Court, or filing a notice of appeal from a decision of the Tax Court”. IRC 7508A(a)(1) lets the IRS specify up to one year to be disregarded for the same acts for taxpayers it determines are affected by a federally declared disaster, significant fire, or terroristic or military action; whether a particular client's petition deadline is covered depends on the terms of the disaster announcement. See disaster postponements.

The late petition. Whether a late petition is fatal now depends on the circuit. In Hallmark Research Collective v. Commissioner, 159 T.C. 126 (2022), the Tax Court, after the Supreme Court's Boechler decision on the collection due process deadline, held that timely filing of a deficiency petition is a jurisdictional requirement, so a late petition must be dismissed and cannot be rescued by equitable tolling. In Culp v. Commissioner, 75 F.4th 196 (3d Cir. 2023), the Third Circuit held that because Congress did not clearly state that the 6213(a) deadline is jurisdictional it is not, that it is presumptively subject to equitable tolling, and remanded for the Tax Court to decide whether the taxpayers were entitled to tolling. In Buller v. Commissioner, No. 24-1557 (2d Cir. Aug. 14, 2025), the Second Circuit agreed with Culp, holding that 6213(a) is a nonjurisdictional claim-processing rule subject to equitable tolling, and reversed the Tax Court's dismissal. Hallmark remains the Tax Court's own precedent, while Culp and Buller control cases appealable to the Third and Second Circuits, so a late petition should plead the facts supporting tolling, identify the circuit of appeal, and still be filed as soon as possible; none of these decisions helps a client who simply waited.

What the notice does

1. Restricts assessment and collection. No assessment, levy or court collection until the period ends or a Tax Court decision is final. An assessment made during the restriction can be enjoined (IRC 6213(a)).
2. Suspends the statute. The assessment period is suspended while assessment is barred and for 60 days after (IRC 6503(a)). IRM 4.8.9.24.4 notes there is no exception for invalid notices.
3. Caps the deficiency. In a reconsideration before the period ends, the IRS cannot increase the amount; new issues come only from the taxpayer (IRM 4.8.9.25.2.1). If a petition is filed, IRC 6212(c) bars a further notice for the same year, except for fraud and the listed exceptions, and the IRS can assert an increase only in the Tax Court under IRC 6214(a).
4. Starts the docketed path. A petition puts the case on the Tax Court docket; Appeals generally gets the case for settlement consideration.

The options during the 90 days

Treat the petition date as fixed whatever else is happening. The campus response letter after a notice says it plainly: “You may continue to work with us to resolve your tax matter, but we cannot extend your time to petition the U.S. Tax Court.” The same is true of Appeals and the Taxpayer Advocate Service. If any doubt remains near the deadline, a petition preserves every option.

Rescission

IRC 6212(d) lets the IRS rescind a notice with the taxpayer's consent. Under IRM 4.8.9.30, “A notice of deficiency may only be rescinded with the consent of both the IRS and the taxpayer,” either side can initiate, and Rev. Proc. 98-54 sets the procedure. The agreement is made on Form 8626, Agreement to Rescind Notice of Deficiency, prepared in duplicate, signed by the taxpayer and countersigned by the Technical Services group manager; it is effective on the date the Commissioner's delegate countersigns, and an executed copy goes to the taxpayer (IRM 4.8.9.30.6). A substitute document works only if it identifies the notice, represents that the ASED has not expired and no petition has been filed, and states that rescission returns both sides to their pre-notice rights, including the IRS's right to issue another notice (IRM 4.8.9.30.6.1). Ask for the countersigned copy before treating the notice as withdrawn; until then the petition clock is running. The IRS will usually rescind only when doing so makes sense for both sides, for example where new information shows the tax due is less than the notice amount (IRM 4.19.13.16). A rescinded notice does not count for Tax Court purposes, but IRC 6212(d) adds: “Nothing in this subsection shall affect any suspension of the running of any period of limitations during any period during which the rescinded notice was outstanding.” If the IRS declines to rescind, the petition deadline still runs.

Default and after

If there is no petition and no agreement by day 105 (165 for notices mailed abroad), the case defaults and is closed for assessment (IRM 4.8.9.28). The tax is then assessed and collection notices follow. After default, the remaining routes are an audit reconsideration with new information while the assessment is unpaid, a doubt as to liability offer, or paying and filing a refund claim. In a collection due process hearing, IRC 6330(c)(2)(B) allows a challenge to the underlying liability only if the taxpayer did not receive a statutory notice of deficiency or did not otherwise have an opportunity to dispute it; see CDP hearings.

Questions practitioners ask