26 U.S.C. § 2: Definitions and special rules

whose spouse died during either of his two taxable years immediately preceding the taxable year, and who maintains as his home a household which constitutes for the taxable year the principal place of abode (as a member of such household) of a dependent (i) who (within the meaning of section 152, determined without regard to subsections (b)(1), (b)(2), and (d)(1)(B) thereof) is a son, stepson, daughter, or stepdaughter of the taxpayer, and (ii) with respect to whom the taxpayer is entitled to a deduction for the taxable year under section 151. if the taxpayer has remarried at any time before the close of the taxable year, or unless, for the taxpayer’s taxable year during which his spouse died, a joint return could have been made under the provisions of section 6013 (without regard to subsection (a)(3) thereof). the date on which the determination is made under section 556 of title 37 of the United States Code or under section 5566 of title 5 of such Code (whichever is applicable) that such individual died while in such missing status, or except in the case of the combat zone designated for purposes of the Vietnam conflict, the date which is 2 years after the date designated under section 112 as the date of termination of combatant activities in that zone. is married at the close of the taxpayer’s taxable year, and is not a dependent of such individual by reason of section 152(b)(2) or 152(b)(3), or both, or any other person who is a dependent of the taxpayer, if the taxpayer is entitled to a deduction for the taxable year for such person under section 151, or maintains a household which constitutes for such taxable year the principal place of abode of the father or mother of the taxpayer, if the taxpayer is entitled to a deduction for the taxable year for such father or mother under section 151. an individual who is legally separated from his spouse under a decree of divorce or of separate maintenance shall not be considered as married; a taxpayer shall be considered as not married at the close of his taxable year if at any time during the taxable year his spouse is a nonresident alien; and a taxpayer shall be considered as married at the close of his taxable year if his spouse (other than a spouse described in subparagraph (B)) died during the taxable year. if at any time during the taxable year he is a nonresident alien; or subparagraph (H) of section 152(d)(2), or paragraph (3) of section 152(d). For purposes of this part, an individual shall be treated as not married at the close of the taxable year if such individual is so treated under the provisions of section 7703(b). In the case of a nonresident alien individual, the taxes imposed by sections 1 and 55 shall apply only as provided by section 871 or 877. For definition of taxable income, see section 63.