26 U.S.C. § 6013: Joint returns of income tax by husband and wife

no joint return shall be made if either the husband or wife at any time during the taxable year is a nonresident alien; no joint return shall be made if the husband and wife have different taxable years; except that if such taxable years begin on the same day and end on different days because of the death of either or both, then the joint return may be made with respect to the taxable year of each. The above exception shall not apply if the surviving spouse remarries before the close of his taxable year, nor if the taxable year of either spouse is a fractional part of a year under section 443(a)(1); in the case of death of one spouse or both spouses the joint return with respect to the decedent may be made only by his executor or administrator; except that in the case of the death of one spouse the joint return may be made by the surviving spouse with respect to both himself and the decedent if no return for the taxable year has been made by the decedent, no executor or administrator has been appointed, and no executor or administrator is appointed before the last day prescribed by law for filing the return of the surviving spouse. If an executor or administrator of the decedent is appointed after the making of the joint return by the surviving spouse, the executor or administrator may disaffirm such joint return by making, within 1 year after the last day prescribed by law for filing the return of the surviving spouse, a separate return for the taxable year of the decedent with respect to which the joint return was made, in which case the return made by the survivor shall constitute his separate return. Except as provided in paragraph (2), if an individual has filed a separate return for a taxable year for which a joint return could have been made by him and his spouse under subsection (a) and the time prescribed by law for filing the return for such taxable year has expired, such individual and his spouse may nevertheless make a joint return for such taxable year. A joint return filed by the husband and wife under this subsection shall constitute the return of the husband and wife for such taxable year, and all payments, credits, refunds, or other repayments made or allowed with respect to the separate return of either spouse for such taxable year shall be taken into account in determining the extent to which the tax based upon the joint return has been paid. If a joint return is made under this subsection, any election (other than the election to file a separate return) made by either spouse in his separate return for such taxable year with respect to the treatment of any income, deduction, or credit of such spouse shall not be changed in the making of the joint return where such election would have been irrevocable if the joint return had not been made. If a joint return is made under this subsection after the death of either spouse, such return with respect to the decedent can be made only by his executor or administrator. after the expiration of 3 years from the last date prescribed by law for filing the return for such taxable year (determined without regard to any extension of time granted to either spouse); or after there has been mailed to either spouse, with respect to such taxable year, a notice of deficiency under section 6212, if the spouse, as to such notice, files a petition with the Tax Court within the time prescribed in section 6213; or after either spouse has commenced a suit in any court for the recovery of any part of the tax for such taxable year; or after either spouse has entered into a closing agreement under section 7121 with respect to such taxable year, or after any civil or criminal case arising against either spouse with respect to such taxable year has been compromised under section 7122. Where both spouses filed separate returns prior to making the joint return—on the date the last separate return was filed (but not earlier than the last date prescribed by law for filing the return of either spouse); Where only one spouse filed a separate return prior to the making of the joint return, and the other spouse had less than the exemption amount of gross income for such taxable year—on the date of the filing of such separate return (but not earlier than the last date prescribed by law for the filing of such separate return); or Where only one spouse filed a separate return prior to the making of the joint return, and the other spouse had gross income of the exemption amount or more for such taxable year—on the date of the filing of such joint return. For purposes of section 6511, a joint return made under this subsection shall be deemed to have been filed on the last date prescribed by law for filing the return for such taxable year (determined without regard to any extension of time granted to either spouse). If a joint return is made under this subsection, the periods of limitations provided in sections 6501 and 6502 on the making of assessments and the beginning of levy or a proceeding in court for collection shall with respect to such return include one year immediately after the date of the filing of such joint return (computed without regard to the provisions of paragraph (3)). such sum shall be treated as the amount shown on the joint return, any negligence (or disregard of rules or regulations) on either separate return shall be treated as negligence (or such disregard) on the joint return, and any fraud on either separate return shall be treated as fraud on the joint return. For purposes of section 7206(1) and (2) and section 7207 (relating to criminal penalties in the case of fraudulent returns) the term “return” includes a separate return filed by a spouse with respect to a taxable year for which a joint return is made under this subsection after the filing of such separate return. For purposes of sections 15, 443, and 7851(a)(1)(A), where the husband and wife have different taxable years because of the death of either spouse, the joint return shall be treated as if the taxable years of both spouses ended on the date of the closing of the surviving spouse’s taxable year. if both have the same taxable year—as of the close of such year; or if one dies before the close of the taxable year of the other—as of the time of such death; an individual who is legally separated from his spouse under a decree of divorce or of separate maintenance shall not be considered as married; and if a joint return is made, the tax shall be computed on the aggregate income and the liability with respect to the tax shall be joint and several. an individual is in a missing status (within the meaning of paragraph (3)) as a result of service in a combat zone (as determined for purposes of section 112), and the spouse of such individual is otherwise entitled to file a joint return for any taxable year which begins on or before the day which is 2 years after the date designated under section 112 as the date of termination of combatant activities in such zone, such election shall be valid even if such individual died before the beginning of such year, and except for purposes of section 692 (relating to income taxes of members of the Armed Forces, astronauts, and victims of certain terrorist attacks on death), the income tax liability of such individual, his spouse, and his estate shall be determined as if he were alive throughout the taxable year. A member of a uniformed service (within the meaning of section 101(3) of title 37 of the United States Code) is in a missing status for any period for which he is entitled to pay and allowances under section 552 of such title 37. An employee (within the meaning of section 5561(2) of title 5 of the United States Code) is in a missing status for any period for which he is entitled to pay and allowances under section 5562 of such title 5. An election described in this subsection with respect to any taxable year may be made by filing a joint return in accordance with subsection (a) and under such regulations as may be prescribed by the Secretary. Such an election may be revoked by either spouse on or before the due date (including extensions) for such taxable year, and, in the case of an executor or administrator, may be revoked by disaffirming as provided in the last sentence of subsection (a)(3). for purposes of chapter 1 for all of such taxable year, and for purposes of chapter 24 (relating to wage withholding) for payments of wages made during such taxable year. This subsection shall be in effect with respect to any individual who, at the close of the taxable year for which an election under this subsection was made, was a nonresident alien individual married to a citizen or resident of the United States, if both of them made such election to have the benefits of this subsection apply to them. An election under this subsection shall apply to the taxable year for which made and to all subsequent taxable years until terminated under paragraph (4) or (5); except that any such election shall not apply for any taxable year if neither spouse is a citizen or resident of the United States at any time during such year. If either taxpayer revokes the election, as of the first taxable year for which the last day prescribed by law for filing the return of tax under chapter 1 has not yet occurred. In the case of the death of either spouse, as of the beginning of the first taxable year of the spouse who survives following the taxable year in which such death occurred; except that if the spouse who survives is a citizen or resident of the United States who is a surviving spouse entitled to the benefits of section 2, the time provided by this subparagraph shall be as of the close of the last taxable year for which such individual is entitled to the benefits of section 2. In the case of the legal separation of the couple under a decree of divorce or of separate maintenance, as of the beginning of the taxable year in which such legal separation occurs. At the time provided in paragraph (5). to keep such books and records, to grant such access to such books and records, or to supply such other information, If any election under this subsection for any two individuals is terminated under paragraph (4) or (5) for any taxable year, such two individuals shall be ineligible to make an election under this subsection for any subsequent taxable year. any individual is a nonresident alien individual at the beginning of any taxable year but is a resident of the United States at the close of such taxable year, at the close of such taxable year, such individual is married to a citizen or resident of the United States, and both individuals elect the benefits of this subsection at the time and in the manner prescribed by the Secretary by regulation, If any election under this subsection applies for any 2 individuals for any taxable year, such 2 individuals shall be ineligible to make an election under this subsection for any subsequent taxable year. Except as provided in paragraph (2), the amendments made by subsections (a) and (b) [amending this section and section 66 of this title ] shall apply to all taxable years to which the Internal Revenue Code of 1986 [formerly I.R.C. 1954] applies. Corresponding provisions shall be deemed to be included in the Internal Revenue Code of 1939 and shall apply to all taxable years to which such Code applies. Subsection (b) of section 66 of the Internal Revenue Code of 1986, as added by subsection (b), shall apply to taxable years beginning after December 31, 1984 . a joint return under section 6013 of the Internal Revenue Code of 1954 was filed before January 1, 1985 , on such return there is an understatement (as defined in section 6661(b)(2)(A) of such Code) which is attributable to disallowed deductions attributable to activities of one spouse, the amount of such disallowed deductions exceeds the taxable income shown on such return, without regard to any determination before October 21, 1988 , the other spouse establishes that in signing the return he or she did not know, and had no reason to know, that there was such an understatement, and the marriage between such spouses terminated and immediately after such termination the net worth of the other spouse was less than $10,000, to the extent that they relate to chapter 1 or 5 of the Internal Revenue Code of 1986 [formerly I.R.C. 1954, sections 1 et seq. and 1491 et seq. of this title, respectively], shall apply to taxable years ending on or after December 31, 1975 , and to the extent that they relate to wage withholding under chapter 24 of such Code [section 3401 et seq. of this title], shall apply to remuneration paid on or after the first day of the first month which begins more than 90 days after the date of the enactment of this Act [ Nov. 6, 1978 ].” Except as otherwise expressly provided in this section, the amendments made by this section [see Tables for classification] shall take effect on the first day of the first month which begins more than 90 days after the date of the enactment of this Act [ Oct. 4, 1976 ]. The amendments made by this section, when relating to a tax imposed by chapter 1 or chapter 2 of the Internal Revenue Code of 1986 [formerly I.R.C. 1954], shall take effect with respect to taxable years beginning after December 31, 1976 .”