At what income does the SALT deduction start to phase out in 2026?

At $505,000 of modified adjusted gross income ($252,500 for married filing separately). Above that line the $40,400 cap falls by 30 cents per dollar of excess MAGI under IRC §164(b)(7), hitting its $10,000 floor at roughly $606,333. For 2025 the threshold is $500,000, the cap is $40,000, and the floor is reached at $600,000.

Is the 45.5% marginal tax rate from the SALT phase-out real, or an internet exaggeration?

It is real arithmetic, not a loophole theory. A dollar of income in the 35% bracket pays 35 cents, and the same dollar removes 30 cents of SALT deduction, which costs another 10.5 cents: 45.5 cents total. It happens automatically on Schedule A, so there is nothing to elect and nothing for the IRS to challenge. For income that lands in the 32% bracket the same mechanism produces 41.6%.

Can the SALT phase-out reduce my deduction below $10,000?

No. Section 164(b)(7) stops the reduction at $10,000 ($5,000 for married filing separately), so every itemizer keeps at least the old TCJA-era cap through 2029. In 2030 the cap is scheduled to revert to $10,000 for everyone and the phase-down disappears with it.

Can married couples avoid the SALT phase-out by filing separately?

No. Married filing separately halves everything: a $20,200 cap, a $252,500 threshold, and a $5,000 floor in 2026. A couple with $560,000 of joint MAGI who split it evenly ends up with a combined cap of $23,900 either way, and separate filing usually forfeits other benefits, so it is a fee, not a fix.

Does a Roth conversion count toward the SALT phase-out threshold?

Yes. Conversion income raises AGI, and therefore MAGI, dollar for dollar. A conversion that lands inside the $505,000 to $606,333 band is effectively taxed at 45.5% federal, which wrecks the usual conversion math. Convert in years that stay under the threshold, or in years already past the band where the cap is pinned at $10,000 anyway.

The Journal / Income Tax

The SALT Deduction Phase-Out Over $500,000 Is a Hidden 45.5% Tax Bracket.

By Ewan Morkel, EAJuly 19, 20266 min read

Between $505,000 and about $606,333 of MAGI, the $40,400 SALT cap shrinks 30 cents per dollar, so every extra dollar is taxed at 45.5%, not 35%. How the 2026 phase-down works, and the moves that keep income out of the band.

A software engineer in San Jose finishes 2026 at $560,000 of income after a larger-than-usual RSU vest. Between California withholding and property tax she paid $55,000 in state and local taxes, and she read that the new tax law raised the SALT cap to $40,400. Her return disagrees: her cap is $23,900. That is the SALT deduction phase-out over $500,000 doing its work, and it means the vest that pushed her into the phase-out range was taxed at an effective federal rate of 45.5%, not the 35% printed on the bracket table.

The mechanics

How the SALT deduction phase-out over $500,000 works.

The One Big Beautiful Bill Act (P.L. 119-21, §70120) raised the cap on the state and local tax deduction from $10,000 to $40,000 for 2025 and $40,400 for 2026, with 1% increases each year through 2029 and a scheduled drop back to $10,000 in 2030. The same section wrote the clawback into IRC §164(b)(7): the cap shrinks by 30% of the amount by which modified adjusted gross income exceeds the threshold, $500,000 in 2025 and $505,000 in 2026, half those figures for married filing separately. MAGI here means AGI plus foreign earned income excluded under §911 and the possession exclusions in §931 and §933, so for nearly everyone it is plain AGI.

Two details matter. First, this is a slope with a floor, not a cliff. The cap never drops below $10,000, so even at $2 million of income you deduct what you did under the old law, and the damage has a ceiling: the most the phase-down can take is $30,400 of deduction in 2026, worth $10,640 in tax at 35%. Second, the test runs on AGI, not taxable income. Itemized deductions, including the SALT deduction itself and charitable gifts, do nothing to keep you under the threshold. Only things that reduce AGI count.

The real rate

Inside the band, 35% becomes 45.5%.

Run the math on one extra dollar earned at $550,000 of MAGI. The dollar itself is taxed at 35%. It also strips 30 cents off the SALT cap, and losing 30 cents of deduction costs another 10.5 cents of tax (30% of 35%). Total: 45.5 cents on the dollar, before state tax. The phase-down works like a stealth bracket that outranks the top statutory rate of 37%, and it sits exactly where RSU vests, bonuses, and good business years land.

Worked example: a $55,000 RSU vest inside the band, single filer, 2026.

MAGI before the vest: $505,000
MAGI after the vest: $560,000
State and local taxes paid: $55,000
SALT cap at $505,000 MAGI: $40,400
Phase-down: 30% of the $55,000 excess: ($16,500)
SALT cap at $560,000 MAGI: $23,900
Taxable income added: $55,000 + $16,500: $71,500
Federal tax on the vest: 35% of $71,500: $25,025
Effective federal rate on $55,000 of income: 45.5%

Tax year 2026, single filer, itemizing, with state and local taxes paid above the cap both before and after the vest. The whole band sits inside the 35% bracket, which runs from $256,225 to $640,600 of taxable income for single filers in 2026. California tax on the vest is on top of this.

The band has hard edges. Below $505,000 of MAGI you keep the full $40,400. Above roughly $606,333 the cap is pinned at $10,000, the phase-down has nothing left to take, and your marginal rate falls back to the bracket table. The 45.5% figure assumes the 35% bracket, which covers the whole band for single filers in 2026; a married couple entering the band while still in the 32% bracket faces 41.6% on those dollars instead. And once taxable income passes $640,600 for a single filer, the separate 2/37 itemized deduction trim I covered in the charitable deduction floor post becomes the haircut that matters.

Planning

Keeping income out of the band.

Because each year's damage tops out at $30,400 of lost deduction, where your baseline sits decides the play. A filer at $550,000 two years running loses $13,500 of cap each year, $27,000 total; concentrating the same income into $650,000 then $450,000 loses $30,400, slightly worse, so mid-band filers should smooth. But a filer at $600,000 twice loses $57,000, while $700,000 then $500,000 loses only $30,400, so filers near the top of the band should bunch. If a liquidity event, a large capital gain, or a Roth conversion is coming, either keep the year fully under $505,000 or land it in a year already past the band. The expensive habit is straddling the upper half of the band two years in a row.

For W-2 earners the levers are the ones that reduce AGI. Maxing a 401(k) takes $24,500 out of MAGI in 2026 (IRS Notice 2025-67), worth $11,148 inside the band at 45.5% instead of $8,575 outside it. An HSA, a deferred compensation election, and harvested capital losses work the same way. Charitable gifts do not: they are below-the-line and never touch MAGI, which surprises a lot of people in December.

Owners of pass-through businesses have a cleaner exit. State pass-through entity taxes move the deduction onto the business return, where neither the $40,400 cap nor the phase-down applies, and OBBBA left that workaround intact. I walked through the election math in the pass-through entity tax post; at $560,000 of MAGI a PTET election is usually worth more than every W-2 lever combined. Filing separately, for the record, is not an exit: married filing separately gets half the cap, half the threshold, and a $5,000 floor, and the arithmetic lands you in the same place with fewer options.