SALT Cap Impact Calculator
See how the $10,000 state-and-local-tax (SALT) cap limits your deduction and what the lost deduction costs you in tax.
How it works
Deductible SALT = min(state/local tax + property tax, $10,000) · Lost deduction = total − cap · Tax cost = lost × marginal rate
The 2017 tax law caps the combined deduction for state and local income (or sales) taxes plus property taxes at $10,000 per return, or $5,000 if married filing separately. Amounts above the cap simply cannot be deducted, which hits high-tax states hardest. The real dollar cost of that lost deduction is the excess multiplied by your marginal tax rate.
Worked example
A single filer paying $8,000 in state income tax and $6,000 in property tax has $14,000 of SALT but can deduct only $10,000. The $4,000 above the cap, at a 24% marginal rate, costs about $960 in extra federal tax.
Frequently asked questions
What is the SALT deduction cap?
It limits the total deduction for state and local income (or sales) taxes plus property taxes to $10,000 per return — $5,000 for married-filing-separately filers.
Which taxes count toward the cap?
State and local income taxes (or sales taxes, if you choose those instead) plus real-estate and personal-property taxes. You cannot exceed $10,000 combined even if each category alone is large.
How do I know what the cap costs me?
Take the SALT you paid above $10,000 and multiply by your marginal tax rate. That is the federal tax you owe purely because the deduction is capped.
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Educational estimate, not tax advice. Uses recent federal parameters that change yearly and ignores your full situation — confirm with a tax professional or the IRS.