All legally married same-sex couples are required to file their federal income tax returns using one of two filing statuses: married filing jointly or married filing separately.
Before this happens, though, it will be important to understand marriage criteria in the eyes of the IRS. A same-sex couple is considered married if they were joined in a legal union on or before the last day of the tax year. For example, a same-sex couple married on Dec. 31, 2014, in a state that recognizes same-sex marriages, will need to file a joint return for the 2014 tax year.
It's also important to compare the benefits of married filing jointly versus married filing separately. In general, married filing jointly offers greater tax benefits, but there are some instances in which spouses will want to file as married filing separately, such as when a spouse's refund will be taken by the government.
Married filing separately status also limits deductions and credits that would otherwise be available under a married filing jointly status. These limitations include the inability to deduct student loan interest, tuition or fees, and the inability to claim a Child and Dependent Care Credit or Earned Income Credit.
In addition, when spouses enter a married filing separately status, both must make the same deductions — either by claiming the standard deduction or by itemizing their deductions [source: Wicker].