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Is 22% Enough on Your RSUs?
Estimate how federal withholding on vesting RSUs compares with the tax the income may add, using 2026 federal figures.
RSU Tax Withholding Calculator
How This Calculator Works
The Model
When RSUs vest, the value of the shares is taxed as wages. Employers usually withhold federal income tax at the flat supplemental rate: 22% on supplemental wages up to $1 million in the calendar year and 37% on the amount above $1 million. Your actual tax depends on your total income and bracket, so withholding can fall short of, or exceed, the tax the RSU income adds.
Key Calculations
- Withholding: 22% × RSU income up to the $1M supplemental-wage mark, plus 37% × the rest
- Tax attributable to RSUs: 2026 federal tax on (other income + RSU income − standard deduction) minus the tax on (other income − standard deduction)
- Gap: tax attributable minus the amount withheld
- FICA (informational): 6.2% Social Security up to the $184,500 wage base, 1.45% Medicare, and 0.9% Additional Medicare Tax above $200,000 (single) / $250,000 (joint)
Assumptions
- Standard deduction; no credits, itemized deductions, or other adjustments
- Withholding on your other wages is assumed to cover the tax on those wages
- All income is ordinary; capital gains, AMT, and NIIT are not modeled
- All wages come from one employer (Social Security and Additional Medicare withholding can differ with several employers)
- State tax is not calculated; the optional state rate shows only what might be withheld
Estimated shortfall: $15,301 on $300,000 of RSU income.
Estimated federal picture on $300,000 of RSU income
Federal withholding
$66,000
22% supplemental rate
Estimated federal tax on RSUs
$81,301
27.1% effective; top bracket 35%
Estimated shortfall
$15,301
May be owed at filing
What this can mean.On these inputs, the flat supplemental withholding is below the estimated tax the RSUs add. Common ways people address a gap include quarterly estimated payments, a higher W-4 withholding on regular pay, or electing a higher withholding rate on vests where the employer allows it. Underpayment penalties generally do not apply if total payments meet the IRS safe harbor (for example, 100% of last year's tax, or 110% if last year's AGI was over $150,000). A CPA can confirm what fits your situation.
Social Security and Medicare (informational)
| Tax | On RSU income |
|---|---|
| Social Security (6.2% to $184,500 of wages) | $0 |
| Medicare (1.45%) | $4,350 |
| Additional Medicare Tax (0.9%), estimated liability | $2,700 |
| Additional Medicare Tax, employer withholding (wages over $200,000) | $2,700 |
Employers withhold Additional Medicare Tax on wages over $200,000 regardless of filing status, so for joint filers withholding and liability can differ. Assumes a single employer.
Hypothetical, illustrative estimate using 2026 federal figures. It uses the standard deduction and ignores credits, other deductions, capital gains, AMT, NIIT, state and local tax, and multiple-employer situations. Actual withholding and tax can differ. This is not tax, legal, or investment advice; consult your CPA before acting, including on estimated payments or safe-harbor planning. It should not be used, on its own, to decide whether to buy, sell, or hold any security. Calculations run in your browser; nothing you enter is sent or stored.
All computation happens in your browser. No data leaves your device.
Common questions
Why is 22% withheld on my RSUs when my tax bracket is higher?
How do people usually cover an RSU withholding shortfall?
Are RSUs also subject to Social Security and Medicare tax?
This calculator is provided for educational purposes only and its results are hypothetical and illustrative. It is an estimate that ignores tax credits, other deductions, AMT, and state tax, and it does not constitute tax, legal, or personalized investment advice. Consult your CPA before making withholding or estimated-payment decisions. It should not be used, on its own, to decide whether to buy, sell, or hold any security. Calculations run in your browser; nothing you enter is sent or stored.
Brought to you by Rubric Advisors
Related guides
RSUs Explained: Vesting, Withholding, and Selling Decisions
An RSU is a promise to deliver company shares once vesting conditions are met. The value is taxed as wages at vesting, and withholding often falls short.
Selling RSUs After an IPO: Withholding, Lockups, and a Sell Plan
RSUs are taxed as wages when they vest; after an IPO, a written sell plan helps manage under-withholding, lockups, and concentration.
Form W-4 and Tax Withholding: Getting Your Paycheck Withholding Right
Form W-4 tells your employer how much federal income tax to withhold. Update it after life or income changes so your refund or balance due stays small.
Estimated Tax Payments: Who Owes Them, Due Dates, and Safe Harbors
If withholding won't cover your tax, quarterly estimates are due April 15, June 15, Sept. 15, and Jan. 15. Safe harbors avoid the underpayment penalty.
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