If a husband or wife changes his or her resident status during the taxable year, while the other spouse maintains his or her status as a resident or nonresident during the entire taxable year (this situation frequently arises when a resident marries a nonresident), the spouse who changes residence during the taxable year must, unless excused under section 154.1(b) of this Part, file two New York State personal income tax returns for that year. One New York State personal income tax return must be filed on form IT-201 for the portion of the year during which such spouse was a resident, and the other New York State personal income tax return must be filed on form IT-203 for the portion of the year during which such spouse was a nonresident. The spouse who did not change his or her residence during the taxable year must file a separate New York State personal income tax return on form IT-201 or form IT-203 (whichever is applicable) without regard to the change made by the other spouse. (For computation of tax liability where there has been a change of residence, see the rest of this Part.)