Massachusetts SALT Cap Calculator (4% Surcharge)
Enter your MAGI and total state + local taxes below. The estimate applies the OBBBA cap and phase-out line by line — no tax software, no signup.
The short answer: Sean — at the scenario numbers pre-loaded below, the OBBBA deduction is $26,000, worth about $9,100 in federal income tax at a 35% marginal rate ($350 per biweekly paycheck). Exact figures update live as you change the inputs.
⚠️ This calculator provides estimates for informational and educational purposes only. It is not tax advice. Results are based on the One Big Beautiful Bill Act (OBBBA) and IRS Schedule 1-A. Consult a qualified tax professional for your specific situation.
Your State's Slice of the $40,000 Cap
The 4% surtax on income over $1M makes Massachusetts the phase-out stress test: at $540,000 MAGI, the cap has already stepped down from $40,000 — $4,000 over the threshold trims $400 of cap. Above roughly $760,000 MAGI the cap floors at $10,000, restoring the pre-OBBBA world. High earners here should model RSU and bonus timing against the $100-per-$1,000 slope.
The full rules, caps and phase-outs for every deduction are in one table on the OBBBA rules page.
Worked Example
Sean and his wife report $540,000 MAGI and pay $38,000 of Massachusetts tax including the surtax.
- • Deductible amount: $26,000
- • Federal income tax savings: $9,100 (at the 35% marginal rate)
- • Per biweekly paycheck: $350
Your actual state tax bill sets the input; the cap and phase-out above set the ceiling — the calculator reconciles both.
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Frequently Asked Questions
How does the Massachusetts surtax interact with the cap phase-out?
The surtax raises your SALT paid, but above $500,000 MAGI the cap itself shrinks $100 per $1,000 of MAGI. At high incomes the cap floors at $10,000 regardless of how much state tax you pay — model both moving parts together.
Which taxes count toward the SALT deduction?
State and local income taxes (or sales tax if you elect that instead) plus real property taxes, up to the OBBBA cap after any income phase-out. Federal taxes never count.