2027 Tax Brackets: A 17-Point Gap Between AI Pay and AI Sales, and a Permanent $40,800 Cap Nobody Priced

Rev. Proc. 2026-35 adjusted about 70 inflation-linked items for tax year 2027 — brackets, the standard deduction, the alternative minimum tax exemption, the zero-rate capital gains window, the child tax credit — and applies to returns filed in 2028. Every rate was left exactly where the 2025 reconciliation law put it, which means no future inflation release can move a rate again.

The 2027 base rose 3.11% to 3.25% depending on the line — the 37% single-filer threshold at $661,375, the standard deduction at $16,600, the alternative minimum tax exemption at $93,000 — while September's consumer prices rose 3.7% and the Fed's September projections put the policy rate at a 4.1% median for both 2026 and 2027. Indexing the base below prices is a permanent, annual tax increase.

The top of the schedule is where this bites hardest. A household now has to earn 3.24% more to stay in the same 37% bracket while its prices rise 3.7%, so the real threshold falls every year and the cohort paying 37% grows without a single rate increase. For the AI complex the marginal worker — an engineer whose vesting income pushes taxable income past $661,375 — crosses that line at a permanently higher cost.

Restricted stock units and options pay out as ordinary income, so an AI engineer's vesting is taxed at the permanent 37% rate plus the 3.8% net investment income tax — 40.8%. The same dollar earned as a long-term capital gain is taxed at 20% plus 3.8% — 23.8%. That 17-point gap is the fiscal drag nobody priced, and the Nov. 5 print is the first time it applies with no expiry date attached.

Two windows matter for timing. The zero-rate capital gains ceiling widens to $51,050 for single filers from $49,450, and the alternative minimum tax exemption rises to $93,000 from $90,100, so a sale completed in January 2027 gets a slightly larger untaxed allowance than one completed in December 2026. Above the 15% ceiling the rate is 20% in either year, so for the largest gains the only deadline that still matters is the December 31 trade date.

The AI complex has never been a cash-flow story for most of its holders, and the 2027 schedule makes that explicit: gains are taxed when sold, not while they sit there, and the rate on that sale no longer carries a scheduled expiry. The money that is already cash sits in the parts of the chain that sell physical scarcity, and it is already being spent. Deferral applies to the gains, not to the cash.

Strip out the thresholds and 2027 contains one genuinely new transfer to households: the Saver's Match, which from this year pays 50% of the first $2,000 of eligible retirement contributions, up to $1,000 per person, replacing the old Saver's Credit. The IRS had not yet published 2027 contribution limits when the brackets were released; forecasters put the 401(k) employee limit near $25,500 against $24,500 in 2026 and the IRA limit near $8,000 against $7,500. Matched savings have to land in an account, and accounts need a recordkeeper.

This is where the tax print has an income statement. The rules it sets are administered by payroll processors on Jan. 1, by tax software during filing season, by recordkeepers and managers on every contribution, and by brokers on every realization — while the AI equity itself stays in taxable accounts, taxed at 23.8% federally plus state tax the moment it is sold. The cash flows run through the administrators.

The Nov. 5 print raises nobody's tax rate and does not need to. It converts the AI trade's after-tax economics from an estimate into a schedule: 40.8% on vesting compensation, 23.8% federally on a long-term sale, a zero-rate window of $51,050, an alternative minimum tax exemption of $93,000, and a state tax deduction capped near $40,800 and rising 1% a year. With those numbers fixed, the investable consequence is not that AI stocks are cheap or dear — it is that tax-advantaged accounts and their administrators capture the flows the code now rewards.