Why would you not treat the couple as you would any heterosexual couple on these points? Whatever your firm's policy is for documentation, that is what you should follow. If the couple says they are married, why wouldn't you accept that? Don't you accept their word from "straight" couples? The State of MD has recognized same sex marriages for the last 2 1/2 years, so I am assuming you haven't had any of these returns to prepare yet. The partners' change of names is a matter of choice, and in some states has been difficult for one or both to change names. It is a matter of state law at this point about the limitations on name changes. If the state allows, they may each retain their existing names just as some heterosexual couples do also, one may choose to take the name of his or her spouse, they may both decide to change names to a hyphenated version of both names, or they may decide on an entirely new name that establishes an identity of their family. Really, I'd just ask them like you would any other newly married couple if they've notified the SSA of any name change and if the SS cards you are presented accurately reflects their current names since being married. You might also consider asking if they have a preference about whose name appears as the primary name on the returns.