Your filing status decides which tax brackets apply, which credits and deductions you can claim, and the adjusted gross income (AGI) your return reports.
For married physicians with federal student loans, the AGI on the return is often why the question comes up: income-driven repayment plans generally look at it. That makes the tax cost of each filing status a number worth knowing before you file.
Filing separately can lower the income shown on one spouse's return, but it often raises the couple's total tax. The useful number is the tax difference between the two ways of filing.
What Filing Separately Can Cost
Separate returns use narrower brackets, and they lose or limit several benefits, including the student loan interest deduction and the education credits. If one spouse itemizes, the other must itemize too.
Those costs vary with your incomes, your state, and your deductions, so a rule of thumb rarely gives the right answer for a specific couple.
