26 CFR § 301.6503(a)-1 - Suspension of running of period of limitation; issuance of statutory notice of deficiency.
(a) General rule.
(1) Upon the mailing of a notice of deficiency for income, estate, gift, chapter 41, 42, 43, or 44 tax under the provisions of section 6212, the period of limitation on assessment and collection of any deficiency is suspended for 90 days after the mailing of a notice of such deficiency if the notice of deficiency is addressed to a person within the States of the Union and the District of Columbia, or 150 days if such notice of deficiency is addressed to a person outside the States of the Union and the District of Columbia (not counting Saturday, Sunday, or a legal holiday in the District of Columbia as the 90th or 150th day), plus an additional 60 days thereafter in either case. If a proceeding in respect of the deficiency is placed on the docket of the Tax Court, the period of limitation is suspended until the decision of the Tax Court becomes final, and for an additional 60 days thereafter. If a notice of deficiency is mailed to a taxpayer within the period of limitation and the taxpayer does not appeal therefrom to the Tax Court, the notice of deficiency so given does not suspend the running of the period of limitation with respect to any additional deficiency shown to be due in a subsequent deficiency notice.
(2) This paragraph may be illustrated by the following example:
(3) For provisions relating to suspension of the running of the period of limitation with respect to collection of “second tier” excise taxes (as defined in section 4963) until final resolution of a refund proceeding described in sections 4961 and 7422 for the determination of the taxpayer's liability for the second tier taxes, see § 53.4961-2 (e)(4).
(b) Corporations joining in consolidated return. If a notice under section 6212(a) with respect to a deficiency in tax imposed by subtitle A of the Code for any taxable year is mailed to a corporation, the suspension of the running of the period of limitation provided in section 6503(a)(1) shall apply in the case of corporations with which such corporation made a consolidated income tax return for such taxable year. Under § 1.1502-77(a) of this chapter (Income Tax Regulations), relating to consolidated returns, notices of deficiency are mailed only to the common parent.