Couples have one big question to answer: file separately when married, or file jointly ?

Just under 5% of the approximately 56 million married couples filed their taxes jointly in 2013, according to IRS statistics. But that doesn’t necessarily mean that filing jointly is right for you every year.

The IRS advises that you and your spouse will “generally” pay less in combined taxes if you file jointly, but it advises couples to figure their taxes both ways to make sure of that.

Just what we all need: Double the aggravation at tax time. You can skip that exercise if you understand the key differences between the two methods of filing.

You Probably Want to File Jointly…

  • If you have children. Some “miscellaneous” deductions and credits are not ordinarily allowed if you are married, but filing separately. Notably, these include the childcare credit, the deduction for student loan interest, and the credit for adoption expenses. The full list of exclusions can be found here.
  • If one of you earned most or all of the income. The joint filing allows for double the deductions for some expenses, notably for a contribution to a retirement savings account. As a couple, you can reduce your tax bill and boost your retirement income at the same time, if you take full advantage of this doubled deductibility.

You May Want to File Separately…

  • When one of you has unusually high deductible expenses. Some deductible costs, notably the medical expenses’ deduction, have a “floor.” Say one of you had a huge medical bill that is not covered by your health insurance. You’re owed a deduction of costs that exceed 10% of gross adjusted income, or 7.5% if you’re 65 or older. (These numbers may change in the future.) That floor may be within reach on your income. Similarly, unreimbursed business expenses can be deducted only if they exceed 2% of adjusted gross income (AGI). If each of your files separately, the spouse with big expenses may qualify for a meaningful deduction, based on that smaller AGI.
  • If each of you earns about the same amount. By filing separately, you may avoid hitting the higher tax rate that might be levied on your doubled income.

You Want to File Separately…

  • When you don’t trust your spouse! As the IRS points out, by filing jointly you each accept responsibility, legally and financially. To put it bluntly, if you have suspicions that your spouse may not be reporting income or may face a significant tax or penalty bill, it may be advisable to consider filing separately. You can ask later for something called “Innocent Spouse Relief,” but there are no guarantees you’ll get it.
  • That goes double if you are separated or in the process of a divorce. The IRS points out that even a court decree in a divorce case might not protect you from their powers to collect taxes and penalties from you if your ex doesn’t pay up.

There is some icing on the cake, though. As noted above, some childcare credits are “usually” not available to those filing separately. The unusual case, according to the IRS, is separation or divorce.

The Bottom Line of file separately when married

The joint tax return continues to be the preferred choice for most American couples. It is, after all, designed to meet their needs.

A glance at the figures under “Married filing jointly” and “Married filing singly” on the IRS tax tables for 2015 shows that couples filing jointly pay less taxes after their combined taxable income reaches the $9,250 — $9,300 range.

However, if you have a year with an extraordinary event, like a big medical expense or a sudden boost in one partner’s income, you might want to check its impact on your taxes if you file separately.