Marriage Tax Calculator

What this marriage tax calculator does

Marriage changes how income is taxed. Two people who file separate single returns may pay more or less than the same two people filing one joint return. This calculator compares the two outcomes using the federal brackets, the standard deduction, a flat state and local rate, and each spouse's pre-tax retirement contributions.

The result is a marriage bonus when filing jointly costs less, a marriage penalty when it costs more, and neutral when the two totals are equal.

How to use this calculator

1. Select the tax year.
2. Enter each spouse's income and pre-tax retirement contribution.
3. Enter a flat state and local tax rate.
4. Click Calculate to see each person's single-return tax, the joint return, and the difference.

The default example is a couple with $65,000 and $45,000 of income, $10,000 and $6,000 of 401(k) contributions, and a 5% state rate.

Marriage tax formulas

Taxable wages (each spouse) = Income − Pre-tax retirement contribution
Single federal tax = Tax on each spouse's taxable wages using the single schedule
Single state tax = Each spouse's taxable wages × state rate
Single total = Sum of both single federal and state taxes

Joint taxable income = Sum of both taxable wages
Joint federal tax = Tax on joint taxable income using the married-filing-jointly schedule
Joint state tax = Joint taxable income × state rate
Joint total = Joint federal tax + Joint state tax

Difference = Single total − Joint total

A positive difference is a bonus: the couple pays less by filing jointly. A negative difference is a penalty: the couple pays more. The calculator uses the standard deduction for both the single and joint returns.

What the results mean

• Person 1 / Person 2: each spouse's income, taxable wages after retirement contributions, federal tax, and state tax on a single return.
• Single total: the sum of both single returns.
• Joint federal and state tax: the tax on one married-filing-jointly return.
• Joint total: joint federal plus joint state tax.
• Difference: single total minus joint total. Positive is a bonus; negative is a penalty.
• Single vs. joint breakdown: the full-width table compares income, taxable wages, federal tax, state tax, and total tax for two single returns and one joint return.
• Joint taxable income: combined taxable wages after retirement contributions and the joint standard deduction.
• Effective joint rate: joint federal tax divided by combined income.

Assumptions and limitations

This calculator uses the standard deduction only. It does not include itemized deductions, tax credits, the alternative minimum tax, capital gain preferential rates, dependents, the child tax credit, student loan interest, or state-specific brackets. The state tax is a single flat rate applied to taxable wages.

The comparison is between two single returns and one joint return. It does not model married filing separately, head of household, or qualifying surviving spouse. It does not calculate FICA, because the question is whether the income tax changes at marriage, not how payroll taxes are withheld.

Frequently asked questions

What is a marriage bonus?

A marriage bonus occurs when the couple's combined tax on a joint return is lower than the sum of their two single returns. It is most common when one spouse earns much more than the other, because the joint brackets and standard deduction shelter more of the higher earner's income.

What is a marriage penalty?

A marriage penalty occurs when the joint return costs more than two single returns. It is most common when both spouses have similar, relatively high incomes, because the joint brackets are not twice as wide at the top.

Do 401(k) contributions affect the comparison?

Yes. Pre-tax retirement contributions reduce each spouse's taxable wages, which lowers both the single and joint tax. The calculator subtracts them before applying the brackets and the standard deduction.

Does this include state tax brackets?

No. State and local tax is a flat rate you enter. Actual state rules can use brackets, credits, and local taxes, so the state portion is an estimate.

Source

References:

• IRS — Revenue Procedure 2024-40 (2025 inflation adjustments)
• IRS — Revenue Procedure 2025-32 (2026 inflation adjustments)

Disclaimer

This calculator is for informational and educational purposes only. It is not tax advice or a tax return. Marriage tax outcomes depend on the full return, including credits, deductions, and state rules. Confirm the result with a qualified tax professional.