How it works

A useful distinction

Test income distribution within the household

Keep combined ordinary income fixed, then move some income from one person to the other in the simple comparison. Joint tax stays based on the same total, while the two single-scenario taxes may change.

Comparing filing scenarios consistently

A marriage-tax comparison needs the same underlying incomes and supported deductions in both scenarios. Review the year and filing assumptions before interpreting the difference. A change in total modeled tax is not a complete measure of the financial effects of marriage. Credits, eligibility rules, and income types outside the selected branch may require a more complete return calculation.

2026 marriage comparison: formula and assumptions

Compare two single returns with one joint return using standard deductions and ordinary-income brackets.

This comparison excludes credits, itemization, dependents, payroll-tax differences, and other tax provisions. It is not advice about filing status.

2025/2026 ordinary-income comparison: formula and assumptions

Difference = combined ordinary-income tax for two eligible single filers − tax for the joint scenario.

Compare the same ordinary income under each filing scenario. Credits, other taxes and special deductions are excluded; this is not a married-filing-separately comparison. This is a bounded US federal scenario; it does not produce a completed tax return.

2025 / 2026 composed federal marriage comparison: formula and assumptions

Joint tax reduction = person A tax after refundable credits + person B tax after refundable credits − joint tax after refundable credits.

Recalculates income, deductions, senior phaseouts, basic dependent credits, SE tax, Additional Medicare and NIIT for all three scenarios. Same household income and unique dependents are counted once. Other deductions, AMT and special credits require verified scenario amounts. Optional state/local comparisons use independent flat-rate assumptions for each scenario. Federal tax differences are reported separately; this is not a state tax return or an eligibility recommendation. Select the applicable tax year. Dollar ceilings and tax bands use that year’s versioned parameters; 2025 does not include the 2026 nonitemizer charitable deduction, charitable floor, overall itemized reduction or active-business QBI minimum.

Worked example

Reference example currency: USD. These fixed examples do not change with your calculator preferences.

Using the 2026 marriage comparison example:

Inputs

Person A ordinary income ($): 80000
Person B ordinary income ($): 50000

Method

Compare two single returns with one joint return using standard deductions and ordinary-income brackets.

Result

Example result

Two single returns: $12,590.00

One joint return: $11,240.00

Joint return tax reduction: $1,350.00

These are illustrative inputs. Change the values to explore a different scenario.

What to keep in mind

Choose the ordinary-income comparison or the combined 2025/2026 federal scenarios. The combined mode compares eligible single, head-of-household or qualifying-surviving-spouse scenarios with a hypothetical joint scenario.

The combined mode recalculates supported income, Social Security taxation, deductions, dependent credits, self-employment tax, Additional Medicare and NIIT. Enter other qualified deductions and credits separately for each scenario; joint eligibility is not inferred by adding the separate amounts.

Each dependent is entered once, and each taxpayer retains a separate Social Security wage cap. Refundable credits are included in the federal difference; withholding is a payment rather than a change in liability.

Optional state/local results use separate entered rates and bases. They are shown separately from the federal difference. The comparison does not establish filing-status eligibility or a recommendation to marry.

Formula references

References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.

Common questions

How do the marriage-tax comparison modes differ?

The ordinary-income comparison uses the selected brackets and deductions. The composed federal comparison also recalculates its supported income types, additional taxes, and credits for the two individual scenarios and the joint scenario. Separately verified adjustments remain your inputs. Neither comparison implements every rule of a complete return.

Does it decide whether a married couple should file separately?

No. It compares two eligible single-filer scenarios with one joint scenario. Married-filing-separately rules, credits and other taxes require a separate analysis.

Prepared by Finflo. See our methodology and editorial policy. Read the relevant professional-advice limitations.

Marriage Tax Calculator

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