If you are married, you generally have a choice of filing your federal income tax return(s) as married filing jointly (MFJ) or as married filing separately (MFS). Because of a number of special rules, your combined tax will often be lower if you file married filing jointly than if you file married filing separately, but that is not always the case. You should generally calculate your tax both ways to determine which filing status results in the lower total tax.
You and your spouse can file as married filing jointly if you are considered married and you both agree to file a joint return. On a joint return, you and your spouse report your combined income, exemptions, deductions, and credits. You are both responsible for any tax, interest, or penalty due on a joint return.
Alternatively, you and your spouse can file as married filing separately. On a separate return, you each generally report only your own income, exemptions, deductions, and credits. You each are responsible only for any tax, interest, or penalty due on your separate return.
Maybe not unexpectedly, many tax items for MFS are exactly half of the amounts for MFJ:
Some items are not available for MFS:
Other rules that apply to MFS:
If your adjusted gross income (AGI) for MFS is lower than for MFJ, you may be able to deduct a larger amount for certain deductions that are deductible only to the extent they exceed a percentage of your AGI (e.g., medical expenses, casualty and theft losses, and job expenses and other miscellaneous deductions) for MFS. For example, medical expenses are generally deductible only to the extent they exceed 10% of AGI. By claiming medical expenses on a separate return with a lower AGI, the amount of medical expenses that can be deducted may be increased.
In response to a 2013 Supreme Court decision invalidating a key provision of the Defense of Marriage Act, the IRS has ruled that same-sex couples who were legally married in a jurisdiction that recognizes their marriage are treated as married for federal tax purposes, regardless of whether the jurisdiction the couple lives in recognizes same-sex marriages. However, the rule does not apply to registered domestic partnerships, civil unions, or similar formal relationships recognized under state law. As a result, legally married same-sex couples generally must file their 2013 (and future) federal income tax returns as married filing jointly or married filing separately. Also, legally married same-sex couples may wish to consider filing amended returns for earlier years as married filing jointly or married filing separately. State tax treatment of same-sex couples varies widely.