Married same-sex couples will be treated the same as opposite-sex couples for tax purposes, the Obama administration announced on Sep 29, regardless of where they live now.
The Treasury Department, following up on the Supreme Court's ruling in June striking down a key section of the 1996 Defense of Marriage Act, announced that gay and lesbian married couples can file joint federal tax returns
Legally-married same-sex couples generally must file their 2013 federal income tax return using either the “married filing jointly” or “married filing separately” filing status.
Source:
All Legal Same-Sex Marriages Will Be Recognized for Federal Tax Purposes
http://www.treasury.gov/press-center/press-releases/Pages/jl2153.aspx
Federal Tax Tables
http://www.halfpricesoft.com/federal_income_tax_2013.asp