Your RSU vest
Used to calculate your marginal tax bracket
• 2026 federal brackets • 2026 SS wage base $184,500
• Assumes standard deduction (itemizing may change results)
• State rates are simplified marginal rates; CA 13.3% applies >$1M
$4,548 owed at filing
Your employer withholds 22% federal but your marginal rate is 32.0%. Set aside $4,548 for your federal tax bill.
Tax breakdown
32.0% marginal rate
9.3% rate
Up to $184,500 wage base
No wage cap
Income exceeds threshold
39.9% of vest value
Employer withholding
Federal withheld (22% flat)
$22,000
Federal you actually owe
$26,548
Disclaimer
This tool provides estimates for educational purposes only and is not tax advice. Results use simplified 2026 federal brackets and state rates, and do not account for the pro-rata rule, ISO/NSO differences, California SDI, NYC local tax, or your full tax situation. Consult a qualified tax professional before making tax decisions related to equity compensation.
How this is calculated
When RSUs vest, the fair market value is treated as ordinary income. The calculator follows IRS rules for supplemental wages and FICA:
- RSU income = shares vesting × price at vest date. This amount appears on your W-2 as wages.
- Federal tax = tax on (other income + RSU income) − tax on other income alone. This stacks RSU income on top of your other wages, so it is taxed at your marginal rate and above.
- Employer withholds at the flat 22% supplemental rate (IRC §3402(g)). If your marginal rate is higher, you owe the difference at filing.
- FICA: Social Security at 6.2% up to the 2026 wage base of $184,500; Medicare at 1.45% with no cap; Additional Medicare at 0.9% above $200,000 (single) or $250,000 (MFJ).
- State tax = RSU income × simplified marginal state rate. Actual state tax may vary with deductions and progressive brackets.
- Withholding gap = federal tax on RSU − 22% flat withholding. This is the amount you must cover via estimated payments or face underpayment penalties.
Worked example: 500 shares at $200/share = $100,000 RSU income. Other income: $150,000 (single). Marginal rate: 24%. Federal tax on RSU: ~$24,000. Employer withholds 22% = $22,000. Withholding gap: $2,000. FICA: $0 SS (salary already over $184,500 cap) + $1,450 Medicare + $0 Additional Medicare. California state tax (9.3%): $9,300. Total estimated tax: ~$34,750.
Sources
- IRS Publication 15 — Supplemental Wage Withholding
- IRS Topic 427 — Stock Options and RSUs
- IRS Revenue Procedure 2025-32 (2026 brackets)
Reviewed against 2026 figures · Last updated June 11, 2026 · Written by Zhisán
What is RSU Tax Calculator?
When restricted stock units (RSUs) vest, the fair market value of the shares becomes ordinary income — taxed just like salary. The catch: your employer withholds at a flat 22% federal rate (the IRS supplemental wage rate under IRC Section 3402(g)), but if your marginal tax bracket is 32%, 35%, or 37%, you will owe significantly more at tax time. This calculator computes your full federal, state, and FICA tax on a vest event and shows the exact withholding gap you need to cover. RSU taxation is straightforward at vest: the share price multiplied by the number of shares is added to your W-2 as wages. FICA taxes (Social Security up to the $184,500 wage base and Medicare with no cap) also apply. If your total income exceeds $200,000 (single) or $250,000 (married), the Additional Medicare Tax of 0.9% kicks in. The critical planning insight is the withholding gap — the difference between what your employer withholds and what you actually owe. Without estimated tax payments to cover this gap, you could face underpayment penalties. This tool helps you plan ahead by showing the exact amount to set aside.
How to Use
- Enter the number of shares vesting and the price per share on the vest date.
- Enter your other ordinary income for the year (salary, freelance income, etc.) to correctly calculate your marginal bracket.
- Select your filing status and state of residence.
- The calculator shows federal marginal rate, state tax, FICA, total tax, and the withholding gap.
- Use the "Amount to set aside" figure to make a quarterly estimated tax payment.
Why Use This Tool?
Tips & Best Practices
- Pay the withholding gap as estimated taxes the same quarter your RSUs vest (Q1: Apr 15, Q2: Jun 15, Q3: Sep 15, Q4: Jan 15)
- If you sell shares immediately at vest, your capital gain/loss is zero — no capital gains tax
- California (SDI) and New York (NYC local tax) have additional taxes not shown; consult a CPA for these
- If your company allows supplemental withholding elections, ask HR to increase the withholding rate above 22%
- Use the 2026 Social Security wage base ($184,500) — if your salary already exceeds this, you owe no SS on RSU income
Frequently Asked Questions
How are RSUs taxed when they vest?
When RSUs vest, the fair market value (shares × price on vest date) is treated as ordinary income — it is added to your W-2 and taxed at your marginal federal income tax rate, plus state income tax and FICA. Your employer withholds at the 22% IRS supplemental rate for federal. If your real marginal rate is higher, you owe the difference at filing.
What is the RSU withholding gap?
The withholding gap is the difference between the 22% your employer withholds and your actual marginal federal rate. For example, at a 35% marginal rate on a $100,000 vest, the gap is $13,000. This becomes due when you file your tax return unless you pay estimated taxes during the year.
Do I pay Social Security tax on RSUs?
Yes, unless your total wages (salary + RSU income) already exceed the 2026 Social Security wage base of $184,500. If your salary is $200,000, your RSU income has no additional Social Security tax, but still has Medicare (1.45%) and possibly the Additional Medicare surtax (0.9%).
What happens when I sell my vested RSU shares?
Your cost basis is the fair market value at vest. Selling immediately = no capital gain. Holding 12+ months before selling = long-term capital gains rates (0%, 15%, 20%). Holding less than 12 months = short-term capital gains at ordinary income rates. The NIIT (3.8%) also applies to capital gains for high earners.
What does this calculator NOT cover?
This calculator does not model ISO/NSO stock option taxation (which has different rules from RSUs), the 83(b) election, capital gains tax when you sell shares, California SDI tax, NYC local income tax, the alternative minimum tax (AMT), or multi-state tax situations. State rates are simplified marginal estimates. Consult a CPA for your specific equity compensation situation.
Real-world Examples
Tech worker: 500 shares vesting at $200
Single filer with $150,000 salary in California, 500 RSU shares vesting at $200/share.
Shares: 500 | Price: $200 | Other income: $150,000 | Filing: Single | State: CA
RSU income: $100,000 | Federal tax: ~$24,000 (24% marginal) Withholding gap: ~$2,000 | CA state tax: ~$9,300 FICA: $0 SS + $1,450 Medicare Total estimated tax: ~$34,750
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