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RSU Tax Shock CalculatorEnter your vest schedule. See the bill before April.

Your vest notice shows shares and withholding. This shows the missing line: the incremental federal tax those shares can create after the 22% estimate meets your actual 2026 brackets.

Calculate my tax shock
Nothing saved or sent 2026 federal rules Free, no account

The line your vest notice leaves blank

2026
Federal income tax withheld$33,000
Estimated federal income tax$51,830

Estimated filing impact from these RSUs

$18,830

POSSIBLE GAP

Live example: four $37,500 quarterly vests on $233,900 of pre-RSU taxable income.

You are looking at a worked example. Replace the four quarterly vests with your own grant schedule.

Build your 2026 vest schedule

Use gross units before sell-to-cover and the expected fair market value when each award settles.

Tax profile

Filing status

Example figures, replace with yours

Refine payroll assumptions

These numbers affect Social Security, Medicare, and the $1 million supplemental-wage threshold. They do not change the regular federal bracket calculation above.

Vests

Leave withholding blank to use the 22% flat-method estimate, with 37% above $1 million.

Vest 1$37,500
Vest 2$37,500
Vest 3$37,500
Vest 4$37,500

Where the gap shows up

Each vest stacks on the income before it. Later vests can land deeper in the bracket ladder even when the share count stays the same.

Sorted by settlement date
DateMar 15
Vest value$37,500
FIT withheld$8,250
Federal tax$12,455
Estimated gap+$4,205
DateJun 15
Vest value$37,500
FIT withheld$8,250
Federal tax$13,125
Estimated gap+$4,875
DateSep 15
Vest value$37,500
FIT withheld$8,250
Federal tax$13,125
Estimated gap+$4,875
DateDec 15
Vest value$37,500
FIT withheld$8,250
Federal tax$13,125
Estimated gap+$4,875

Worked example

$150,000 of RSUs vesting in four quarterly tranches on a $250,000 salary

A single tech employee earns $250,000 of salary and has $233,900 of taxable income before RSUs (salary minus the $16,100 standard deduction). Four quarterly vests of 250 shares at $150 settle in 2026, and the employer withholds federal income tax at the 22% flat supplemental rate. These are the calculator's own sample inputs.

Inputs

Worked example inputs
Filing statusSingle
Taxable income before RSUs$233,900
Employee wages before RSUs$250,000
Vest schedule4 vests, 1,000 shares at $150
Federal withholdingCalculator estimate (22% flat method)

Calculator output

Worked example calculator output
RSU wages$150,000
Incremental federal income tax$51,830
Federal income tax withheld at 22%$33,000
Social Security tax$0
Medicare tax (regular and additional)$3,525
Estimated gap to cover at filing$18,830

The salary already sits in the 32% bracket, so the $150,000 of RSU wages is taxed at 32% and 35% (an effective 34.6%), while withholding at 22% collects only $33,000. The salary is already above the Social Security wage base, so the vests add no Social Security tax. The gap is owed when the return is filed unless it is covered by extra withholding or estimated payments.

Methodology

How this calculator works

For each vest, in date order, the calculator stacks the vest value on top of your taxable income and the earlier vests, measures the extra federal tax, and compares it with what the employer withholds.

Formulas

  • Federal tax per vest = tax on (taxable income + prior vests + this vest) minus tax on (taxable income + prior vests), using the 2026 brackets.
  • Default withholding = 22% of supplemental wages up to $1 million for the year, 37% above that, unless you enter the actual amount withheld.
  • Social Security = 6.2% of the vest value that falls under the $184,500 wage base; Medicare = 1.45% of the full vest value.
  • Additional Medicare tax = 0.9% of household Medicare wages over $200,000 single or head of household, $250,000 married filing jointly; withholding uses the $200,000 employer threshold.
  • Filing gap = federal income tax + Additional Medicare tax minus federal income tax withheld and Additional Medicare withheld.

Assumptions

  • Ordinary stock-settled RSUs that settle on the vest date, taxed as W-2 wages at fair market value.
  • You enter taxable income before RSUs, after your deductions.
  • One employer, so the Social Security wage base is tracked against the wages you enter.

What it ignores

  • State and local income tax, AMT, and NIIT.
  • Capital gains on shares sold after vesting, and credits or deductions that phase out as income rises.
  • Deferred-settlement awards, multi-employer Social Security refunds, and multi-state sourcing.

Sources

Primary sources

  1. IRS Publication 15 (2026): Employer's Tax Guide: supplemental wage withholding at 22% and 37%
  2. Treas. Reg. 31.3402(g)-1: supplemental wage payments: mandatory 37% withholding over $1 million
  3. IRS Revenue Procedure 2025-32: 2026 tax brackets and standard deduction
  4. Internal Revenue Bulletin 2025-45: publishes Rev. Proc. 2025-32 and the 2026 brackets
  5. 26 U.S. Code Section 83: property transferred for services: RSU value taxed as compensation when the shares are delivered
  6. SSA: 2026 contribution and benefit base: Social Security wage base and payroll tax rates
  7. 26 U.S. Code Section 3101: FICA tax on employees: Social Security, Medicare and Additional Medicare rates and thresholds
  8. IRS: questions and answers for the Additional Medicare Tax: return threshold vs. employer withholding threshold

Written by Bryan Martin, CPA, Managing Partner and Founder of Taxstra. Last reviewed October 20, 2026. Taxstra is a CPA firm serving 1,000+ clients in all 50 states.

Educational, not individualized tax advice.

The 22% is a collection method. It is not your tax rate.

The return stacks RSU wages on top of the taxable income already in your household. The calculator measures that bracket-by-bracket difference, then compares it with the amount expected to leave the vest.

Read the RSU withholding guide
What the estimate follows
2026 federal brackets and the taxable income you enter
22% flat supplemental method and 37% above $1 million
6.2% Social Security up to the 2026 wage base
Regular and Additional Medicare tax, including the MFJ mismatch
Per-vest actual federal withholding overrides
Outside this estimate: state and local tax, AMT, NIIT, credits and deduction phaseouts, capital gains, multi-employer payroll corrections, and awards that do not settle when they vest.

Year-end 2026

Do this before Dec 31: RSU and stock option moves

Equity pay is taxed on dates you do not fully control: vest, exercise, and sale. What you can control before the year closes is withholding, exercise timing, and the losses you harvest.

  1. 1

    Close the RSU withholding gap

    Employers usually withhold federal tax on RSU income at the flat 22% supplemental rate (37% on supplemental wages over $1 million). If your bracket is 32%, 35%, or 37%, the difference shows up as a balance due in April. Add up your 2026 vests and cover the gap with extra withholding or an estimated payment.

  2. 2

    Decide on any ISO exercise with AMT in view

    Exercise ISOs and hold the shares past December 31, and the spread counts toward the alternative minimum tax for 2026. Model the AMT before you exercise. If a same-year sale makes more sense, it removes the AMT adjustment and the spread is taxed as ordinary income instead.

  3. 3

    Harvest losses, and watch the wash sale rule

    Losses on sales made by December 31 offset 2026 gains plus up to $3,000 of ordinary income. A new RSU vest or ESPP purchase of the same stock within 30 days before or after a loss sale can trigger the wash sale rule and defer the loss.

  4. 4

    Fix any underpayment before January 15

    The fourth 2026 estimated payment is due January 15, 2027. Extra withholding from a December paycheck counts as paid evenly through the year, so it can cure earlier underpayments that a late estimate cannot. Check your safe harbor.

A free 30-minute call with our team about your needs, how we can help, and whether we are a good fit. Tax planning slots are limited before year-end.

Educational only, not individualized tax advice. 2026 federal rules; state rules and your facts can change the answer.

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Questions the number usually raises

How are ordinary RSUs taxed?

For a typical stock-settled award that settles when it vests, the fair market value of the shares at settlement is compensation reported as W-2 wages. It is subject to ordinary federal income tax and payroll tax. This calculator is not designed for double-trigger awards, deferred settlement, Section 83(i) deferral, or awards that settle in a different year.

Why can 22% withholding leave a tax bill?

Twenty-two percent is an optional federal withholding method for separately identified supplemental wages at or below $1 million. It is not the final tax rate. If your RSU income lands in the 24%, 32%, 35%, or 37% bracket, the return can calculate more tax than payroll withheld. Employers may also use an aggregate payroll method, so use the per-vest override when you know the actual federal withholding.

What does “taxable income before RSUs” mean?

Enter your best estimate of 2026 ordinary taxable income before adding these RSU wages. That is household income after deductions, not gross salary. The sample uses $250,000 of income less the $16,100 single standard deduction, or $233,900. Using taxable income lets the tool stack each vest into the correct federal brackets without pretending to calculate every deduction and credit on your return.

Why are payroll taxes separate from the surprise number?

Social Security and regular Medicare are generally withheld when the RSUs become wages, so they reduce what reaches you but usually do not create the later income-tax gap. The headline compares incremental regular federal income tax plus any Additional Medicare mismatch with the amounts payroll is expected to withhold for those items.

Do RSUs get taxed twice when I sell?

Not when basis is reported correctly. The amount included in W-2 wages generally becomes the stock basis. A later sale produces capital gain or loss only on the price movement after settlement. Verify the basis shown by the broker before filing, because a missing or zero basis can overstate gain.

Is this my predicted refund or balance due?

No. It estimates the incremental federal filing impact of the entered RSUs. Your full return also depends on regular paycheck withholding, a spouse’s withholding, credits, itemized deductions, investment income, estimated payments, AMT, state tax, and other facts this focused calculator does not model.

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