Rev. Rul. 2013-17, I.R.B. 2013-38

(homosexual persons whose relationship is recognized as a legal "marriage" under state law will be treated as married persons for federal tax law purposes; thus such persons can later reside in state that does not recognize homosexual marriage and file a joint return; such persons can (but don't have to) amend returns to claim joint filing status for open tax years in which such persons married (but can't amend return to file single return); such persons can no longer file as single taxpayer; ruling inapplicable to state taxes; ruling specifically uses term "legal" to make clear that it is limited in application to states in which homosexual marriage is legal (and does not apply to civil unions, etc.), but is silent with respect to its application to homosexual marriage in states where such unions are not legal but are allowed; while U.S. Supreme Court opinion in Windsor directed at equal protection for homosexual couples, ruling uses phrase "same sex" rather than homosexual, and, therefore, has application to same-sex, non-homosexual marriages; ruling completely contrary to position of Social Security Administration (SSA) taken in Program Operations Manual System (POMS) in which SSA says that all claims filed on or after Jun. 26, 2013, or that were pending final determination as of that date, can be paid when the Number Holder was married in a state that permits homosexual marriage and is domiciled at the time of the application or while the claim is pending a final determination in a state that recognizes homosexual marriage;  SSA's position consistent with Sec. 216(h)(1)(A)(I) of SSA which determines family status by looking to courts of state in which individual domiciled and whether that state would consider applicant validly married at time of application; the 31 states that bar the state from recognizing a homosexual marriage granted in another state will need to enact legislation decoupling from federal definition).