I was under the impression it was usually lower taxes (partially selection bias due to it being lower for myself). As the other commenter points it, it is complicated and sometimes lower/sometimes higher to file jointly.
Interestingly, the current tax structure somewhat encourages single income families.
Taxes for married filing jointly are usually lower than for married filing separately.
But taxes for married filing jointly are often higher than for two single filers. This is especially true for higher incomes.
As a really simple example, consider two people both with $100k in taxable income, after taking their standard deductions and personal exemptions, in 2016. As single filers they would pay $21036.75 each in taxes, for a total of $42073.50. If they were married filing jointly, they would pay $42985.50, which is more. That happens because while the first two bracket boundaries (10% to 15% and 15% to 25%) are twice as big for joint married filers as they are for single filers, after that the boundaries start to converge. At the very top, the 39.6% boundary starts at $415k for single filers and at ~$467k for married filers....
There are also nasty perverse incentives where if one member of a married couple has a high income the other one can't contribute to IRAs in ways they could if they were just filing as an individual filer.
bzbarsky|9 years ago
But taxes for married filing jointly are often higher than for two single filers. This is especially true for higher incomes.
As a really simple example, consider two people both with $100k in taxable income, after taking their standard deductions and personal exemptions, in 2016. As single filers they would pay $21036.75 each in taxes, for a total of $42073.50. If they were married filing jointly, they would pay $42985.50, which is more. That happens because while the first two bracket boundaries (10% to 15% and 15% to 25%) are twice as big for joint married filers as they are for single filers, after that the boundaries start to converge. At the very top, the 39.6% boundary starts at $415k for single filers and at ~$467k for married filers....
There are also nasty perverse incentives where if one member of a married couple has a high income the other one can't contribute to IRAs in ways they could if they were just filing as an individual filer.