The SALT Deduction: What It Covers and What the New Cap Really Allows

SALT is shorthand for state and local taxes, and the deduction covers three buckets. First, state and local income taxes: withholding on your W-2, quarterly estimates, and any balance due you paid this year for a prior year. Second, as an alternative to income taxes, state and local general sales taxes; you pick whichever is larger, which matters mostly in states with no income tax, where sales tax is the only option. Third, property taxes: real estate taxes on homes you own, plus value-based personal property taxes such as the ad valorem portion of a vehicle registration.

What does not count trips people up. Federal income and payroll taxes are never deductible here. Neither are transfer taxes on a home sale, HOA dues, utility charges, or special assessments that fund a specific improvement like a new sewer line (those add to the property's basis instead). Taxes on a rental or business property skip Schedule A entirely and deduct without any cap on Schedule E or the business return, a distinction that becomes a full-blown strategy in Section 5.

The deduction exists for a principled reason: it keeps the federal government from taxing income the state already took. The cap exists for a fiscal one: limiting it pays for other tax cuts. The tug-of-war between those two ideas is why the numbers in the next section keep moving.

Before 2018 there was no dollar cap; itemizers deducted their full state and local tax bill. The 2017 tax law capped it at $10,000, unindexed, which quietly tightened every year as state taxes and home values rose. The One Big Beautiful Bill Act reset the number: $40,000 for 2025, $40,400 for 2026, then increases of about 1% a year through 2029. In 2030 the cap is scheduled to fall back to $10,000. Married filing separately gets half of each figure at every step.

The timeline shape matters for planning. A five-year window rewards moving deductible state taxes into the window and, where you control timing, front-loading them into years when your income sits below the phase-down threshold. It also argues against long-term strategies that only pencil out if the $40,000-plus cap is permanent, because as written, it is not.

Congress did not want the bigger cap flowing to the highest earners, so it attached a phase-down. For 2026: once modified adjusted gross income passes $505,000, the $40,400 cap shrinks by 30% of the excess. It stops shrinking at $10,000, the old cap, which the math reaches at roughly $606,000 of MAGI. The thresholds are the same for single and joint filers, a marriage penalty hiding in plain sight; married filing separately uses half the numbers.

The band between $505,000 and $606,000 deserves respect. Inside it, earning one more dollar costs tax on that dollar plus the tax value of 30 cents of lost deduction. For a taxpayer in the 37% bracket, that is an effective marginal rate north of 48% on income inside the band. If your income hovers near the threshold, timing moves suddenly carry double weight: deferring a bonus, spreading a large capital gain across years (see our California capital gains guide for how brutal the state layer can get), or sizing a Roth conversion to stop just under the line can each preserve tens of thousands of dollars of deduction.

SALT is an itemized deduction, so it competes with the standard deduction: $16,100 single, $32,200 married filing jointly, $24,150 head of household for 2026. You claim SALT only if your total itemized deductions, SALT plus mortgage interest plus charitable gifts plus the rest, beat those numbers. Under the $10,000 cap, roughly nine in ten filers took the standard deduction. The $40,000-plus cap changes that calculus for a specific group: households with big state tax bills and a mortgage.

If you are near the crossover, bunching finishes the job: pay January's property installment in December and stack two years of charitable giving into one, then take the standard deduction the off year. The mechanics of that dance live in our standard deduction guide.

The SALT cap applies to individuals. It does not apply to businesses. Nearly every state with an income tax now offers a pass-through entity tax (PTET): the S corporation or partnership elects to pay the owner's state income tax at the entity level, deducts it as an ordinary business expense with no cap, and the owner claims a state credit (or exclusion) for the tax the entity paid. The IRS blessed the structure in Notice 2020-75, more than 36 states adopted a version, and the 2025 law, after early drafts threatened to kill it, left it fully intact.

The traps are procedural, which is exactly why this is consult territory. Most states require the election, and often an entity-level estimated payment, by a fixed date, sometimes as early as March or June of the tax year; miss it and the year is gone. Multi-state owners have to check whether their home state credits another state's PTET. Cash flow moves from the owner to the entity, which changes quarterly planning. And the deduction generally reduces QBI-relevant income too, so the interaction with the 20% pass-through deduction needs modeling, not assuming. If you do not have a pass-through entity yet, the SALT angle joins the payroll-tax math in the S corp election guide.

1. The state refund boomerang.

Deduct state income tax this year, get a state refund next spring, and the refund is federally taxable to the extent the deduction actually helped you. Bigger caps mean bigger deductions, which resurrects a problem the $10,000 cap had mostly buried. Clean fix: size your state estimates accurately instead of banking a refund.

2. Overpaying state tax on purpose does not work.

Prepaying property tax that has not been assessed is not deductible, and inflated state estimated payments made purely to manufacture a deduction can be treated as deposits, not taxes. Timing real liabilities is planning; inventing liabilities is not.

3. Your state probably does not mirror the federal rules.

The SALT cap is a federal rule. States write their own deduction rules, and most never adopted the federal cap because states generally do not let you deduct their own income tax anyway. Some states cap property tax deductions differently, some disallow them, and state responses to the 2025 federal changes are still rolling out. The federal return and the state return are two different chess boards; our state and local tax planning guide covers the multi-state layer.

4. The band math can flip a good idea into a bad one.

A Roth conversion, a large asset sale, or a one-time bonus that drags MAGI through the $505,000 to $606,000 band does not just get taxed; it erases up to $30,400 of SALT deduction on the way through. Model big income events against the phase-down before pulling the trigger, not after.