Same-sex couples, legally married in jurisdictions that recognize their marriages, will be treated as married for federal tax purposes, regardless of where the couple lives. The rule applies to all federal tax provisions where marriage is a factor, including filing status, claiming personal and dependency exemptions, taking the standard deduction, employee benefits, contributing to an IRA and claiming tax credits.
Same-sex couples may, but are not required to, file original or amended returns choosing to be treated as married for federal tax purposes for one or more prior tax years still open under the statute of limitations, generally three years from the date the return was filed or two years from the date the tax was paid, whichever is later. As a result, refund claims can still be filed for tax years 2010, 2011 and 2012 via Form 1040X. If you were married for those years, you should consult a D.C. Tax Attorney to determine the impact of your federal tax by filing jointly. In most cases, your joint tax liability may be considerably less, subject to the marriage penalty, discussed below.
Equates to higher taxes imposed on some married couples filing that would not be required by two otherwise identical single people with exactly the same income. Penalty occurs in the tax system when a wife and husband pay more income tax filing jointly as a couple than they would if they had remained single and filed as individuals.
Conversely, a bonus occurs if a couple pays less tax filing jointly than they would if they were not married and filed singly. Couples with marriage bonuses far outnumber those incurring marriage penalties but precise estimates are not available . Generally, the earner in a single-income couple usually benefits greatly from filing as a married couple, while the nonearner receives penalties of in the form of higher taxes, depending on shifts in tax rates. As a practical matter, I always calculate tax both ways to determine the tax bonus or penalty.