Sometimes that is the result of filing jointly versus separately. However, there are a number of tax deductions, credits, and other tax provisions that are disallowed or limited when filing separately. For example, the child and dependent credit is not allowed when filing separately, nor is the student loan interest deduction. Filing separately also changes the income threshold for making deductible IRA contributions or Roth IRA contributions. If one or both spouses are taking Social Security, filing separately drastically increases the amount of Social Security income subject to tax.
from my own experience, several years ago, my wife and I got a larger refund from New York State by filing separately even though we paid extra federal income tax. This was due to the way that New York State assigns tax brackets differently from the federal government.
in any particular situation, the only way to know for sure is to try it both ways. But almost all the time, filing jointly is the same or better than filing separately.
