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    Tax / filing status

    Marriage penalty and marriage bonus

    The brackets alone never produce a penalty: the joint bands are exactly twice the single bands up to the 35% threshold, and because tax is progressive, splitting one income across two returns always costs at least as much as filing jointly. The penalty comes from the deductions that do not double — above all the $10,000 SALT cap.

    DirectionPenaltyDeduction, joint$50,000Deduction, apart$60,000
    Marriage penalty
    $2,400
    more tax filing jointly
    Joint tax
    $45,694
    on $250,000 taxable
    Two singles
    $43,294
    on $240,000 taxable
    SALT forfeited
    $10,000
    one $10,000 cap instead of two
    Two returns against one
    The brackets double exactly up to the 35% band, so the difference comes from the deductions that do not.
    +$2,400
    Two returns against one
    LineFiling separatelyFiling jointly
    Income$300,000$300,000
    Itemised deductions$60,000$50,000
    Deduction used$60,000$50,000
    Taxable income$240,000$250,000
    Federal tax$43,294$45,694
    Difference—+$2,400
    Marginal rate24%24%

    The SALT cap is $10,000 per return. Two itemisers filing separately keep $20,000 of state and local tax; the same couple filing jointly keeps $10,000. That asymmetry, introduced in 2017, is the main source of the two-earner penalty in high-tax states.

    Inspect the model
    Choose a quick result view, a scaled comparison, or the complete diagnostic set.
    Penalty against the income split
    Zero at one earner, worst when the two incomes are similar — the shape of a two-earner penalty.
    Penalty against the income split-1.960e+4-1.470e+4-9802.91-4905.14-7.384890.390%0%4%4%8%8%11%11%15%15%19%19%23%23%26%26%30%30%34%34%38%38%41%41%45%45%50%50%Joint minus separate
    Tax either way
    The gap is small in percentage terms and large in dollars.
    Tax either way0.0001.078e+42.157e+43.235e+44.314e+45.392e+4SeparatelySeparatelyJointlyJointlyDifferenceDifferenceTax
    Canonical equations
    The exact relationships implemented by this engine.

    T(a) + T(b) · Two single returns.

    T_MFJ(a + b − D_joint) · One return, one deduction.

    T_joint − (T_a + T_b) · Positive is a penalty.

    ΣSALT − min(10,000, ΣSALT) · The cap does not double.

    finance methodology

    A clear path from inputs to results.

    The brackets alone never produce a marriage penalty: the joint bands are exactly twice the single bands up to the 35% threshold, and because tax is progressive, splitting one income across two returns always costs at least as much as filing jointly. The penalty comes from the deductions that do not double — above all the $10,000 SALT cap.

    Step-by-step methodWorked exampleAssumptions explained

    How to use

    1. Enter each spouse’s income.
    2. Add state and local tax for each, and any other itemised deductions.
    3. Read the tax both ways and the difference.
    4. Check the threshold at which the penalty starts for your profile.

    The formula

    P=TMFJ(a+b−Djoint)−[T(a−Da)+T(b−Db)]P = T_{MFJ}(a+b-D_{joint}) - \left[T(a-D_a) + T(b-D_b)\right]

    Reference: IRC §1(j) 2025 rate schedules and §164(b)(6) SALT cap; the standard deduction is §63(c).

    Worked example

    Two earners at $150,000 with $30,000 of itemised deductions each

    Inputs
    • Each spouse earns $150,000.
    • Each pays $10,000 of state and local tax and $20,000 of mortgage interest.
    • No other deductions.
    Calculation path
    1. 1

      Filing separately, each itemises $30,000, so taxable income is $120,000 each.

    2. 2

      Tax on $120,000 single is $21,647, so the two returns total $43,294.

    3. 3

      Filing jointly, the SALT cap allows only $10,000 of the $20,000 paid, so itemised deductions are $50,000.

    4. 4

      Taxable income is $250,000 and the joint tax is $45,694.

    5. 5

      The difference is $2,400 — a penalty, created entirely by the cap that does not double.

    Result

    $43,294 separately · $45,694 jointly · $2,400 penalty.

    Interpreting the result

    This is why the marriage penalty is a high-tax-state phenomenon. Two earners who take the standard deduction pay exactly the same either way; two earners who itemise lose $10,000 of SALT deduction by marrying, and the value of that loss is their marginal rate times the forfeited deduction.

    Assumptions & limitations

    • Wages only; no self-employment income, capital gains or credits.
    • The SALT cap is $10,000 per return and is not indexed.
    • Both spouses use the single schedule when filing separately.
    • NIIT, the additional Medicare tax and credit phase-outs are not modelled.

    Frequently asked questions

    Why does filing jointly usually produce a bonus?

    Because the joint brackets are twice the single ones and tax is progressive, so a single earner spreads income over wider bands. That is worth thousands to a one-earner household.

    Does the penalty get worse at high incomes?

    Yes, for two reasons: the 37% threshold is $626,350 single but only $751,600 joint, not double, and the NIIT thresholds of $200,000 and $250,000 do not double either.

    Is the SALT cap permanent?

    It is currently legislated through 2025 and has been the subject of repeated extension and amendment debates, so confirm the year before relying on it.

    So who actually pays the penalty?

    Two earners with similar incomes who itemise, especially in a state with high income or property tax. The SALT cap is the mechanism.

    Can we file separately to avoid it?

    Sometimes, but filing separately usually costs more overall — it halves several credits and thresholds, and the SALT cap is still $10,000 per return, so the gain is limited.

    Methodology last reviewed 2026-10-22. Results are informational and not financial or engineering advice — see our disclaimer.