When return deemed filed

(A) Assessment and collection For purposes of section 6501 (relating to periods of limitations on assessment and collection), and for purposes of section 6651 (relating to delinquent returns), a joint return made under this subsection shall be deemed to have been filed— (i) 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); (ii) 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 (iii) 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 this subparagraph, the term “exemption amount” has the meaning given to such term by section 151(d). For purposes of clauses (ii) and (iii), if the spouse whose gross income is being compared to the exemption amount is 65 or over, such clauses shall be applied by substituting “the sum of the exemption amount and the additional standard deduction under section 63(c)(2) by reason of section 63(f)(1)(A)” for “the exemption amount”.

(B) Credit or refund 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).