Reading the phase-down
The calculator opens with a married couple filing jointly with $560,000 of MAGI, $30,000 of state income tax and $18,000 of property tax. They are $55,000 over the $505,000 threshold. Thirty percent of that is $16,500, so their cap is $40,400 − $16,500 = $23,900. Of the $48,000 they pay, $24,100 is over the cap and can’t be deducted.
They still itemize: $23,900 of SALT, $20,000 of mortgage interest and $2,200 of charity (their $5,000 minus 0.5% of AGI) add up to $46,100, well above the 2026 standard deduction for a couple. Change the MAGI to see the cap move; the row for your income is highlighted in the table.
The range that costs the most
Between $505,000 and about $606,333, every extra $1,000 of MAGI does two things when your state and local taxes are over the cap: it is taxed, and it takes $300 off your SALT deduction. In the 35% bracket that comes to about 45.5 cents of federal tax on each extra dollar instead of 35. Above about $606,333 the cap sits at the $10,000 floor and the effect stops. Below $505,000 it doesn’t apply at all, and it doesn’t apply to anyone whose state and local taxes are under the reduced cap: the deduction then is simply what they paid.
The same works in reverse: a dollar less of MAGI in this range raises the cap by 30 cents, up to $40,400. The table under the calculator shows the cap at each income level.
What counts as MAGI here
For the SALT cap, MAGI is adjusted gross income plus income excluded as foreign earned income or housing, or as income from Puerto Rico or a U.S. territory. Wages, interest, dividends, capital gains, retirement distributions and business income all count. Your filing status matters only at married filing separately, where each spouse’s own MAGI is compared with $252,500.
This page applies the statute’s 2026 figures, section 164(b)(7) as amended by Pub. L. 119-21, as of October 2026. The IRS worksheet for the 2025 Schedule A works the same way with $40,000 and $500,000.