Congratulations, same-sex couples! Thanks to a Supreme Court ruling in 2013, couples who have entered into a valid same-sex marriage must now file federal tax returns using either "married filing jointly" or "married filing separately" status. The ruling applies to couples who were married in a state that legally recognizes same-sex marriage, even if the couple lives in a state that does not [source: IRS Treasury].
Married same-sex couples will also be treated as legally married regarding other tax provisions such as estate and gift taxes. In addition, if you are part of a same-sex married couple, you may be able to amend previous years' tax returns to take advantage of this filing status. It might just result in a refund for you. As you're filing, keep a couple of things in mind. This ruling has nothing to do with state taxes, so if you live in a state that does not recognize your marriage, you will still have to file your state tax returns individually, and the ruling does not apply to domestic partnerships or civil unions.