Marriage Tax Bonus: When You Pay Less Married
A marriage bonus occurs when the combined married income results in lower taxes than the sum of two single returns. Scenarios that create a marriage bonus: One-earner couples: one spouse earns $200,000, the other earns nothing — the same $200,000 spread across the married brackets (which are double the single brackets through most income levels under TCJA) reduces the effective rate. Dual-earner couples with large income gap: one earns $150,000, the other earns $30,000. As singles: $150,000 earner is in the 24% bracket; $30,000 earner is in the 12% bracket. As married ($180,000 combined): much of the income falls in the 22% bracket. Single high earner with zero-income spouse: one spouse earns $700,000. As single: 37% on income above $626,350. As married: 37% threshold is $751,600 MFJ — significant bracket benefit on the top portion.
Marriage Tax Penalty: When You Pay More Married
A marriage penalty occurs when the tax on combined married income exceeds the sum of two single returns. The penalty exists when the married brackets are not exactly double the single brackets. 2026 penalty zone at the top: 37% bracket: single starts at $626,350; MFJ starts at $751,600 (less than double = PENALTY). The penalty is most pronounced for two-earner couples where BOTH spouses earn above $626,350 (the single 37% threshold). As married, they hit 37% on combined income above $751,600; as singles, each had the full $626,350 in lower brackets before hitting 37%. Example: two spouses each earning $700,000 total $1.4M. As singles: each pays 37% on $73,650 ($700K – $626,350) = $27,250 each = $54,500 total at 37%. As married: $1.4M – $751,600 = $648,400 at 37% = $239,908 at top rate. The additional penalty from the lower MFJ threshold = significant.
SALT Cap and Marriage Penalty
For 2026–2029, the One Big Beautiful Bill Act (OBBBA) raised the SALT cap to $40,000 for married filing jointly and $20,000 for single filers — exactly double the single amount — eliminating the SALT marriage penalty for most couples. Under the old $10,000 flat cap (2018–2025): singles each deducted up to $10,000 ($20,000 combined); married couples deducted only $10,000 total — a $10,000 lost deduction costing $2,400 in extra tax at the 24% rate. Under the 2026 OBBBA cap: singles each deduct up to $20,000; MFJ couples deduct up to $40,000 — identical totals, no penalty. Exception: MAGI above $500,000 triggers a 30% phase-out. At $700,000 MFJ MAGI, the effective cap is reduced by $60,000 ($200K × 30%), potentially to zero — high earners in CA/NY/NJ still feel the pinch. For married filing separately: cap remains $10,000. The cap reverts to $10,000 flat in 2030, at which point the SALT marriage penalty returns.
IRMAA Medicare Surcharge: Hidden Marriage Penalty for Retirees
IRMAA (Income-Related Monthly Adjustment Amount) is an additional Medicare Part B and D premium surcharge for high-income beneficiaries. IRMAA thresholds (2026, approximate): Single: surcharge begins at $106,000; MFJ: surcharge begins at $212,000. The MFJ threshold is exactly double the single threshold for the first tier. However, at higher IRMAA tiers, the married thresholds are less than double the single thresholds, creating a penalty. For couples where one spouse earns $200,000 and the other $50,000: as singles, $200K earner triggers IRMAA but $50K does not. As married ($250K combined): the couple is assessed at the married MFJ threshold for that combined income tier — potentially a higher IRMAA tier than either would face alone. The IRMAA marriage penalty most affects retired couples where one spouse has high investment/pension income that alone would clear the IRMAA threshold.
ACA Premium Tax Credits and the Marriage Penalty or Bonus
ACA marketplace subsidies create one of the most significant marriage-related tax issues for lower-to-middle-income households. As singles: each person is assessed individually for subsidies based on their own income vs federal poverty level (FPL). Two single individuals with $40,000 each in income may each qualify for significant ACA subsidies. As married ($80,000 combined): the combined $80,000 is compared to the married FPL threshold — eliminating or reducing subsidies compared to single status. The benefits cliff: for couples near the 400% FPL threshold, marriage can trigger sudden loss of ACA subsidies worth thousands annually. This has led to couples intentionally delaying marriage to preserve individual ACA subsidy eligibility — a perverse incentive created by the ACA household income calculation.
Married Filing Separately: When It Helps and When It Hurts
Married Filing Separately (MFS) can sometimes reduce the marriage penalty — but has significant downsides. MFS limitations: most tax credits (EITC, Child and Dependent Care, American Opportunity Credit, Premium Tax Credit) are eliminated or reduced; student loan interest deduction is disallowed; IRA deductibility is severely restricted if either spouse has a workplace plan; Social Security taxation is calculated differently (less favourable); capital loss carryover is halved. When MFS can help: one spouse has very high income and the other has significant medical expenses that need a lower AGI denominator to clear the 7.5% threshold; avoiding IRMAA surcharges (if one spouse is on Medicare and the other is not, MFS can separate incomes for IRMAA purposes); student loan income-driven repayment (IDR) — MFS keeps the lower-income spouse's IDR payments lower even though it increases taxes.