The quadrupled deduction for state and local taxes was the headline win for high-tax-state households in the July tax law. The fine print, laid out in an August 20, 2025 Venable analysis, is less generous: the higher cap melts away for incomes above $500,000, and changes to the alternative minimum tax will pull more high earners back toward that parallel system starting in 2026.
What changed
For 2025 through 2029, the cap on itemized deductions for state and local income, sales and property taxes rises from $10,000 to $40,000, or $20,000 for married individuals filing separately. Both the cap and the income threshold grow by 1% a year starting in 2026. After 2029, the limit reverts to $10,000.
The catch is a phase-down. The $40,000 cap is reduced by 30% of the amount by which modified adjusted gross income exceeds $500,000 ($250,000 for separate filers). The reduction stops at a $10,000 floor, so no one ends up worse off than under the old cap.
The law also permanently changes the alternative minimum tax. The income levels at which the AMT exemption begins to phase out are set at $500,000 for single filers and $1 million for joint filers, and beginning in 2026 the phaseout rate doubles from 25% to 50% of income above those thresholds. Taxpayers above the thresholds lose their exemption twice as fast as before.
Who is affected
The phase-down zone runs from $500,000 to $600,000 of modified AGI in 2025. Households in that band in California, New York, New Jersey and other high-tax states, where state income and property taxes easily exceed $40,000, feel it most. Below $500,000, most such households get the full new cap. Above $600,000, they are back to $10,000.
The after-tax math
Every additional dollar of income inside the phase-down zone removes 30 cents of deduction. Assume, for illustration, a 35% federal bracket. That lost deduction costs 10.5 cents of tax, so the effective federal rate on that dollar becomes about 45.5%, before state tax and the 3.8% net investment income tax where it applies.
| Modified AGI | Reduction (30% of excess) | SALT cap |
|---|---|---|
| $500,000 | $0 | $40,000 |
| $550,000 | $15,000 | $25,000 |
| $600,000 | $30,000 | $10,000 floor |
| $800,000 | $90,000 | $10,000 floor |
Example: a New Jersey couple with $550,000 of modified AGI and $45,000 in state income and property taxes can deduct $25,000, not $40,000. If a $50,000 year-end bonus lifts them to $600,000, their cap falls to $10,000, and the bonus effectively carries an additional $15,000 of lost deduction on top of its own tax.
The AMT change works in the opposite direction on timing. It takes effect in 2026, and because state and local taxes are not deductible for AMT purposes, households that claim a larger SALT deduction for regular tax may find some of that benefit clawed back if the faster exemption phaseout pushes them into AMT. Exercising incentive stock options is a common trigger.
Moves to discuss with your advisor
- Pass-through entity tax elections. The final law leaves PTET elections untouched, according to both Venable and RSM. Owners of partnerships and S corporations can still have the business pay state tax and deduct it at the entity level, outside the individual cap. RSM notes the analysis depends on state sourcing, credits and owner mix.
- Managing modified AGI. Households near $500,000 often look at pre-tax retirement contributions, timing of bonuses and capital gains, and charitable strategies that reduce income rather than itemized deductions.
- Payment timing. Property tax and estimated state tax payments can sometimes be shifted between years to land in a year with a larger cap.
- AMT modeling for 2026. Equity-compensation holders may want a multiyear projection before exercising options.
What to watch
IRS guidance and 2025 forms will show how the phase-down is computed in practice. The larger planning horizon is 2029: without further legislation, the cap snaps back to $10,000 in 2030, while the tighter AMT phaseout is permanent.
Sources
After TAX is an independent publication. Articles are general information, not tax, legal or investment advice. Consult a licensed professional about your situation.
