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.
For more information, please click on the links provided below.
Article on Same-Sex Marriages Recognized for Federal Tax
Frequently Asked Questions for Individuals of the Same Sex Who Are Married Under State Law
Frequently Asked Questions for Individuals of the Same Sex Who Are in a Registered Domestic Partnership and Civil Union