For federal tax purposes, the IRS looks to state or foreign law to determine whether individuals are married. The IRS has a general rule recognizing a marriage of same-sex spouses that was validly entered into in a domestic or foreign jurisdiction whose laws authorize the marriage of two individuals of the same sex even if the married couple resides in a domestic or foreign jurisdiction that does not recognize the validity of same-sex marriages.
This information reflects the published interpretations of the IRS concerning Revenue Ruling 2013-17 in 2013-38 IRB 201. The best source of information for answers to questions about federal income tax treatment for individuals of the same sex under this interpretation is the IRS itself. The IRS provides information, webinars and videos for this topic on a separate FAQ page of its website for such questions.