All legally married same-sex couples must file federal tax returns as married,
even if the couple lives in a state that doesn’t formally recognize their marriage.
This means they will file their 1040s using joint or married-filing-separate status.
But the rules for state tax filings depend on the law of the state where they reside.
Those living in states that OK their marriage will file state returns as married.
This affects residents of Calif., Conn., Del., D.C., Hawaii, Ill., Iowa, Maine, Md., Mass.,
Minn., N.J., N.M., N.Y., R.I. and Vt. Ditto for N.H.’s tax on interest and dividends.
The same goes for same-sex marrieds residing in Colo., Mo., and Ore.,
even though these three locales currently prohibit same-sex marriage in their states.
Utah has flip-flopped, but now gives these couples a choice to file returns as married.
23 states require same-sex married couples to file separate returns: Ala.,
Ariz., Ark., Ga., Idaho, Ind., Kan., Ky., La., Mich., Miss., Mont., Neb., N.C., N.D., Ohio,
Okla., Pa., S.C., Va., W.Va. and Wis. Also for Tenn.’s tax on interest and dividends.