It’s worthwhile to calculate whether you’d come out ahead as married filing jointly on past federal tax returns. By Kimberly Lankford, Contributing Editor January 23, 2014 Is it worth the hassle for legally married same-sex couples to amend old tax returns to claim the “married filing jointly” status?SEE ALSO: How to Prevent a Big Tax Bill If you were legally married anywhere that sanctioned such unions in 2010, 2011 or 2012, you have the option to amend your federal tax returns from those years to file jointly rather than as two single filers. You aren’t required to amend the returns, but it’s worthwhile to calculate whether you’d come out ahead as joint filers, especially if there’s a big difference in your incomes. “When there is a disparity in income, especially if you have a nonworking spouse, there will be a benefit,” says Jean Nelsen, an enrolled agent in San Francisco. (Enrolled agents are licensed to represent taxpayers before the IRS.) If both spouses work and have similar incomes, they are likely to be hit with the “marriage penalty,” she says, providing little or no benefit to amending the returns. And if both spouses have capital losses or rental real estate losses, deductions for those losses can be limited when couples file joint returns. Nelsen also points out that if one spouse has adopted the other spouse’s children, he or she would lose the adoption credit with an amended return. TurboTax can help you run the numbers with its free TurboTax DOMA TaxCaster tool. Advertisement You have until April 15, 2014, to amend a 2010 return; until April 15, 2015, to amend a 2011 return; and until April 15, 2016, to amend a 2012 return. You need to file a Form 1040X for each year you are amending a return. Nelsen says the procedure is to choose one of the returns that was previously filed as single and use those numbers as the “previously filed amounts” required on the amended return, and add the other spouse’s numbers in the adjustment column. “Document, document, document,” she says. “The more information you can give the IRS as to why you are doing the amended return, the better.” Include details about the change in filing status in the explanation of changes section of the amended return. For more information, see the IRS’s Answers to Frequently Asked Questions for Individuals of the Same Sex Who Are Married Under State Law. Federal tax returns filed by legally married same-sex couples on September 16, 2013, or later must generally be filed as married. That includes 2012 returns with an extension that had not been filed by that date, as well as federal returns for 2013 and later. Got a question? Ask Kim at email@example.com.