The city taxable income of a city resident individual shall be his city adjusted gross income less his city deduction and city exemptions, as determined under this chapter.

(b) Husband and wife.

(1) If the federal taxable income of husband or wife, both of whom are residents, is determined on a separate federal return, their city taxable incomes shall be separately determined.

(2) If the federal taxable income of husband and wife, both of whom are residents, is determined on a joint federal return, their city taxable income shall be determined jointly.

(3) If neither husband or wife, both of whom are residents, files a federal return:

(A) their tax shall be determined on their joint city taxable income, or

(B) separate taxes may be determined on their separate city taxable incomes if they both so elect.

(4) If either husband or wife is a resident and the other is a nonresident, a separate tax shall be determined on the city taxable income of the resident spouse on a separate form unless such husband and wife determine their federal taxable income jointly and both elect to determine their joint city taxable income as if both were residents.