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Vestgap

Methodology

How Vestgap calculates the RSU withholding gap.

Reviewed August 21, 2026. About. Not tax advice.

The gap is computed locally from 2026 federal tax tables (Rev. Proc. 2025-32) and a flat supplemental withhold of 22% on RSUs + bonus. We do not connect banks. We do not file. The dollar figure is a planning estimate; the letter is a list of questions for a licensed CPA.

2026 federal ordinary brackets used here

Single: 10% to $12,400; 12% to $50,400; 22% to $105,700; 24% to $201,775; 32% to $256,225; 35% to $640,600; 37% above. Standard deduction $16,100.

Married filing jointly: 10% to $24,800; 12% to $100,800; 22% to $211,400; 24% to $403,550; 32% to $512,450; 35% to $768,700; 37% above. Standard deduction $32,200.

Supplemental federal withhold on RSUs and bonus: 22% through $1,000,000 in a payroll period, 37% above (Publication 15). Additional Medicare 0.9% over $200,000 single / $250,000 MFJ, only on the slice salary had not already covered.

What we include

Federal ordinary tax on estimated AGI using 2026 single / MFJ brackets and standard deduction. Incremental federal on supplemental vs 22% withheld. Additional Medicare on the slice of income that salary alone had not already pushed over the threshold. A single high-earner state rate minus that state’s supplemental withhold rate.

What we exclude

Itemized deductions, AMT, NIIT on investment income, ISO/AMT, ESPP, QSBS, credits, CA SDI, NYC local beyond a NY simplification, multi-state allocation, household employment tax, and any estimate of what your W-4 already does to salary. If those matter, the letter says so; it does not pretend to price them.

Sources

IRS Revenue Procedure 2025-32 (2026 inflation-adjusted brackets and standard deduction). IRS Publication 15, supplemental wage withholding 22% / 37%. Additional Medicare 0.9% IRC §3101(b)(2) thresholds $200,000 / $250,000. State supplemental rates as commonly applied to equity compensation (CA 10.23%, NY 11.66%); they are not a substitute for state instructions.

FAQ

Who writes the numbers vs the letter?
Brackets, standard deduction, 22%/37% supplemental, additional Medicare 0.9% over $200k/$250k, and simplified state rates are deterministic TypeScript. The CPA email and flags are generated as a memo around those frozen numbers. The model is not allowed to invent amounts.
Why is Texas cheaper on the same vest?
No wage income tax. Austin founder sample (W-2 $160,000 + RSUs $90,000 + other $180,000) still due $68,770, almost all federal — and K-1 other income is not withheld at all.

Sources

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