Legal same-sex marriages recognized by I.R.S.
Starting with the 2013 tax year, if you are in a legal same-sex marriage, you are married for federal tax purposes and must file a joint or separate return. You cannot use the Single filing status.
You are in a legal marriage if you were legally married in a state that recognizes same-sex marriages. Registered domestic partnerships and civil unions do not qualify. Once you are legally married, it does not matter for federal tax purposes if you move to another state.
If you were in a same-sex marriage in prior years, you may be able to file an amended federal tax return for 2010, 2011, and 2012. You are not required to file an amended return. Consult with your tax advisor to see if it would be advantageous for you to file an amended return.
The state of Florida does not recognize same-sex marriages.