What a marriage bonus or penalty means
The comparison is straightforward: calculate each spouse’s tax as a single filer, add those results together, then compare that combined total with one married-filing-jointly return on the same combined gross income. If the joint return produces less tax, the difference is a marriage bonus. If the joint return produces more tax, the difference is a marriage penalty.
For many middle-income couples the result is neutral because the 2025 standard deduction and most federal bracket thresholds are essentially doubled for married filing jointly. The biggest federal differences usually appear when spouses have very uneven incomes or when a high-income couple reaches top brackets that do not scale exactly two-for-one.
Marriage effect = Combined single tax - Joint tax
A positive result is a marriage bonus, a negative result is a marriage penalty, and zero means the federal comparison is neutral.
Taxable income = Gross income - Deduction applied
Each single return and the joint return reduce gross income by the applicable standard deduction or user-entered deduction amount before the 2025 federal brackets are applied.