SALT cap explained

The $10,000 cap is national, but its bite is geographic. Pre-TCJA SALT-deduction data from the IRS Statistics of Income Division (Tax Year 2017 Individual Income Tax Returns, Tables 2.1 and 2.2) and post-TCJA modeling published by the Tax Foundation, the Tax Policy Center, and the Congressional Research Service (CRS Report R45576) consistently show the same handful of states absorbing the overwhelming majority of capped-deduction dollars.

The states with the highest share of itemizers whose pre-TCJA SALT deduction exceeded $10,000 are, in order of intensity: New York, New Jersey, California, Connecticut, Massachusetts, Maryland, Illinois, Oregon, Minnesota, and Hawaii. New York and New Jersey alone account for a disproportionate share of capped-deduction dollars relative to their share of returns. California's effect is driven by sheer population — even at a lower per-capita share of affected itemizers, the absolute count of pass-through owners over the cap is the largest in the country.

The states essentially untouched by the cap are the seven with no individual income tax (Florida, Texas, Nevada, Washington, South Dakota, Wyoming, Alaska) plus the two with very low rates and narrow bases (Tennessee, which finished phasing out its Hall Tax on investment income in 2021, and New Hampshire, which is phasing out its Interest and Dividends Tax through 2025). Property-tax exposure alone keeps a small share of high-asset homeowners in those states over the cap, but the pass-through owner population is largely insulated.

[Specific affected-itemizer percentages vary by source and tax year; verify against the IRS SOI cross-tabulation before citing a single number.]

A common operator confusion: the $10,000 cap is aggregate, not per-category. IRC §164(b)(6) limits the combined deduction for state and local (a) real property tax, (b) personal property tax, (c) state and local income tax (or, at the taxpayer's election, sales tax in lieu of income tax under §164(b)(5)). The same $10,000 ceiling covers all four buckets.

In practice this means a homeowner in a high-property-tax county pays the cap before any state-income-tax deduction is available. A New Jersey owner with $14,000 of annual property tax on a primary residence and $18,000 of New Jersey state income tax allocable to wages and K-1 income reaches the $10,000 cap on property tax alone; the full $18,000 of state income tax is non-deductible at the federal level under the pre-OBBBA cap. Post-OBBBA the ceiling expands but the aggregation rule is unchanged — the combined deduction is bounded by the (post-COLA, post-phaseout) cap figure for that year.

For PTET planning this matters because PTET only rescues the state-income-tax portion of the SALT bill. Property tax remains a personal owner-level deduction subject to the cap (or the un-deducted residue above it). A high-property-tax taxpayer who elects PTET still loses property-tax deduction above the cap; the PTET workaround does not extend to county or municipal real-estate levies.

TCJA §11042 set the SALT cap at $10,000 for joint filers, single filers, and heads of household — but only $5,000 for married-filing-separately (MFS) returns. The asymmetry is statutory, codified at §164(b)(6)(B). For most couples the MFS election is dominated by joint filing on other grounds (loss of joint-only credits, compressed brackets, MFS QBI threshold treatment, the inability of one spouse to itemize when the other takes the standard deduction). For a narrow population the MFS election still matters: spouses with very lopsided pass-through income, or with state-residency mismatches (one spouse a resident of California, the other a resident of Texas, for example), or with one spouse's medical-expense itemization pushing the joint return into AMT territory.

For PTET planning specifically the MFS quirk is rarely binding because the PTET deduction occurs at the entity level — it does not flow through to either spouse's SALT cap. The MFS $5,000 floor matters only for the residual owner-level state tax (the portion of state tax not paid through the entity), property tax, and sales tax. If you are running the MFS comparison and PTET is in the picture, the rule of thumb is: PTET unaffected by MFS, residual SALT capped at $5,000 per spouse.

Before TCJA the federal SALT deduction was unlimited in dollar terms but heavily constrained for high-bracket taxpayers by the Alternative Minimum Tax (AMT). The AMT denied SALT as a deduction entirely in computing alternative minimum taxable income (AMTI) under IRC §56(b)(1)(A)(ii). For a substantial share of pre-TCJA high-bracket itemizers, particularly in the high-tax states, the regular-tax SALT deduction was offset by AMT — the taxpayer paid AMT in approximately the amount of the regular-tax SALT savings, netting close to zero benefit.

TCJA changed two things simultaneously. First, §11042 imposed the $10,000 SALT cap on the regular-tax computation. Second, §12003 raised the AMT exemption ($109,400 joint / $70,300 single for tax year 2018, indexed) and dramatically raised the AMT exemption phaseout threshold (to $1,000,000 joint / $500,000 single), effectively pulling the upper-middle and high-bracket population out of AMT entirely for 2018–2025. The combined effect for many pre-TCJA AMT payers was: lost SALT deduction worth roughly what AMT had been costing them anyway, plus AMT relief. For pre-TCJA non-AMT payers in high-tax states the net effect was straight tax increase.

The post-TCJA AMT exemption levels are scheduled to revert under the same 2025 sunset that originally applied to the cap. OBBBA July 2025 made certain TCJA provisions permanent and extended others; verify the AMT exemption rules and SALT cap year by year against current law before quoting a planning conclusion.

The One Big Beautiful Bill (P.L. 119-21, signed July 2025) modified IRC §164(b)(6) for tax years 2025 through 2029. The structure as commonly summarized:

• Base cap raised from $10,000 to approximately $40,000 (joint), with COLA indexation for subsequent years. • Phaseout commences at $500,000 Modified Adjusted Gross Income (MAGI), where MAGI is defined for this purpose using the cross-references in §164 and incorporates §86 / §911 add-backs. • Cap reduces dollar-for-dollar (or per a defined fraction; verify the precise OBBBA statutory rate against the conference report) above the threshold. • Cap grinds down to a $10,000 floor — the OBBBA structure does not let the cap drop below the pre-OBBBA $10,000 figure. • Cap reverts to $10,000 for all filers in tax year 2030 unless reauthorized. • PTET workaround under Notice 2020-75 explicitly preserved.

Mechanics example: a joint filer with $700,000 MAGI in 2026. Excess over threshold: $200,000. Under the as-summarized linear-grind structure the cap would reduce by some fraction of that $200,000 toward the $10,000 floor. The precise grind rate is the operative number for marginal-rate planning and should be pulled from the OBBBA statutory text or the JCT bluebook score (when published) rather than from secondary summaries.

The planning implication for PTET: for taxpayers materially above the phaseout — which is essentially every pass-through owner large enough for PTET to matter — the residual cap is at or near $10,000 and PTET arbitrage is fully on the table. For taxpayers in the $300,000–$500,000 MAGI band the math is closer and the comparison is annual, depending on property-tax exposure and state-income-tax mix.

[Verify OBBBA grind rate, COLA mechanic, and exact MAGI definition against the statute at every annual content review. Numbers labeled "approximately" should never be quoted as exact in client-facing work.]

Two AMT questions matter for PTET planning. First: does an entity-level PTET payment trigger AMT consequences for the entity? The answer is no for partnerships and S-corps as such (those entities are not subject to AMT under the C-corp AMT regime). The PTET payment is an ordinary deductible business expense at the entity level for both regular-tax and (where relevant) book-income computations.

Second, and more practically: does an owner who claims PTET-arbitrage benefit at the federal level lose the benefit to AMT? Under post-TCJA / post-OBBBA AMT rules the AMT exemption and the AMT phaseout threshold are elevated enough that the bulk of the high-bracket pass-through owner population is outside the AMT zone. The PTET arbitrage produces a federal regular-tax saving that is not clawed back through AMT for most affected taxpayers.

The narrow exception: taxpayers with very large preference items (large ISO exercises, large private-activity municipal-bond interest, large depletion deductions, large pre-TCJA passive-activity-loss carryovers under §469 / §58(c)). Those preference items can pull a taxpayer into AMT regardless of the SALT-cap interaction. For those taxpayers the PTET benefit must be modeled against the AMT-tentative-tax computation — the federal deduction is real, but the marginal-rate uplift on the deduction may be the AMT-tentative rate (26% or 28%) rather than the regular-tax bracket. Consult a preparer running the §55 alternative-minimum computation in parallel with the regular-tax PTET model.