RSU tax calculator: why do I owe tax on my RSUs?
Because the flat 22% withheld at vesting is often too low. RSUs vest as ordinary income, but your employer usually withholds the fixed 22% supplemental rate — while your real bracket may be 32%, 35% or 37%. The difference lands as a bill at filing. Enter your numbers to see what's withheld now and the gap you may owe later.
Your RSUs
What's withheld at vesting
The gap most people miss (at filing)
Worked examples
Single Seattle PM, $42k vest, 32% bracket
What you keep now (after vesting withholding): $29,309
Out of $42,000 vesting, about $12,691 is withheld (30.2%) — you keep $29,309 in shares/cash now.
⚠ The 22% federal withheld is LOWER than your real 32.0% bracket. You'll likely owe about $1,498 more in federal tax at filing on this RSU — set it aside now, don't get surprised in April.
What's withheld at vesting
- RSU value at vesting: $42,000
- Federal supplemental withholding (22%): −$9,240
- Social Security (6.2%, partial — near/over the $184,500 cap): −$589
- Medicare (1.45%): −$609
- Additional Medicare (0.9% over $200k): −$153
- State (5%): −$2,100
- Total withheld at vesting: −$12,691 (30.2%)
- Shares/cash you keep now: $29,309
The gap most people miss (at filing)
- Your real federal tax on this RSU (~32.0% bracket): $10,738 (25.6%)
- Already withheld for federal (22%): −$9,240
- Estimated EXTRA federal you'll owe at filing: +$1,498
Married Bay Area director, $1.25M vest, California tax
What you keep now (after vesting withholding): $791,875
Out of $1,250,000 vesting, about $458,125 is withheld (36.6%) — you keep $791,875 in shares/cash now.
⚠ The 22% federal withheld is LOWER than your real 37.0% bracket. You'll likely owe about $143,253 more in federal tax at filing on this RSU — set it aside now, don't get surprised in April.
What's withheld at vesting
- RSU value at vesting: $1,250,000
- Federal supplemental withholding (22% / 37% over $1M): −$312,500
- Social Security (6.2%, partial — near/over the $184,500 cap): −$0
- Medicare (1.45%): −$18,125
- Additional Medicare (0.9% over $200k): −$11,250
- State (9.30%): −$116,250
- Total withheld at vesting: −$458,125 (36.6%)
- Shares/cash you keep now: $791,875
The gap most people miss (at filing)
- Your real federal tax on this RSU (~37.0% bracket): $455,753 (36.5%)
- Already withheld for federal (22%/37%): −$312,500
- Estimated EXTRA federal you'll owe at filing: +$143,253
Married support rep, small $18k vest, Texas
What you keep now (after vesting withholding): $12,663
Out of $18,000 vesting, about $5,337 is withheld (29.6%) — you keep $12,663 in shares/cash now.
✓ The 22% federal withheld is MORE than your real 12.0% bracket needs. You'll likely get about $1,800 of it back at filing on this RSU.
What's withheld at vesting
- RSU value at vesting: $18,000
- Federal supplemental withholding (22%): −$3,960
- Social Security (6.2%): −$1,116
- Medicare (1.45%): −$261
- Total withheld at vesting: −$5,337 (29.6%)
- Shares/cash you keep now: $12,663
The gap most people miss (at filing)
- Your real federal tax on this RSU (~12.0% bracket): $2,160 (12.0%)
- Already withheld for federal (22%): −$3,960
- Estimated federal refund on this RSU: −$1,800
Examples are recomputed whenever the underlying rates or data change; the date above is the last recompute.
How RSU tax & withholding works & data sources
When RSUs vest, the fair market value of the shares is ordinary wage income (reported in Box 1 of your W-2). Because it's paid apart from regular salary, employers withhold federal income tax at the flat 22% supplemental rate on amounts up to $1,000,000 a year, and a mandatory 37% above $1M. It's also subject to FICA: Social Security 6.2% up to the 2026 wage base of $184,500 (once your year-to-date wages pass that, Social Security stops), Medicare 1.45% with no cap, and an Additional Medicare 0.9% on wages over $200,000. The catch: that flat 22% is withholding, not your final tax. Your RSU income stacks on top of your other income, so your real marginal rate may be 24–37% — and if it's above 22%, you owe the difference when you file. Employers commonly sell or hold back shares ("sell-to-cover") to fund the 22% — which is exactly why higher earners get a surprise bill. A later sale of the shares is a separate capital-gains event, measured from the vest-date value.
Sources: IRS — Pub. 525 (RSUs as wage income) · IRS — Pub. 15 (22%/37% supplemental) · SSA — 2026 wage base ($184,500) · IRS — 2026 tax brackets
Frequently asked questions
Why do I owe taxes on RSUs that were already taxed?
They weren't fully taxed — they were withheld at a flat 22%. If your real marginal bracket is higher (24%, 32%, 35% or 37%), the 22% covered only part of it, and you settle the rest at filing. It feels like a surprise because withholding ≠ final tax.
How much is really taken from my RSUs at vesting?
22% federal, plus Social Security (6.2% up to $184,500 of wages), Medicare (1.45%, plus 0.9% over $200k), and any state rate — often 30–45% withheld in high-tax states. This tool shows the exact split.
How do I avoid the RSU tax surprise?
Estimate your real marginal rate (this calculator does it), set aside the gap above 22%, and consider asking payroll to withhold extra or making a quarterly estimated payment. Selling some shares at vest to cover it is common.
What about when I sell the shares later?
That's a separate event. Your cost basis is the vest-date value already taxed as income. Any gain above it is a capital gain — short-term (ordinary rates) if held ≤1 year, long-term (0/15/20%) if held >1 year — so you're not taxed twice on the same value.