Your RSUs are probably under-withheld. Find out by how much.
Employers withhold a flat 22% on RSU vests — but your real marginal rate is often 24%, 32%, or higher. Free 2026 calculators show your exact shortfall, your ISO/AMT exposure, your ESPP tax split, and your quarterly estimated-payment plan.
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Enter your RSU vests, ISO exercises, and ESPP purchases manually — or import them from a broker template (CSV or Excel).
See your true tax picture
RSU withholding gap, ISO/AMT exposure, your ESPP ordinary-vs-capital split, and quarterly estimated payments. The free calculators run entirely in your browser — nothing leaves your device.
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Four tax surprises every equity-comp employee should check
The 22% trap
Your employer withholds 22% on every vest. If you're in the 24% or 32% bracket, you owe the difference every April — plus possible underpayment penalties.
Your broker's 1099-B is probably wrong
Brokers usually report your ESPP cost basis without the discount you already paid tax on. Miss the adjustment and you're taxed twice on the same dollars.
The six-figure exercise surprise
Exercising incentive stock options triggers no regular tax — but the spread counts for AMT. Big exercises can create a five-figure tax bill with zero cash to pay it.
The quarterly penalty trap
Under-withheld equity income means you may owe quarterly estimated payments. Miss them and the IRS adds underpayment penalties on top of the tax bill.
Start with the guides
Why your RSU withholding is wrong
The 22% flat withholding vs. your real marginal rate — with a worked example.
ESPP taxes: qualifying vs. disqualifying dispositions
The two holding-period tests and how each one splits your gain.
ISO exercises and AMT, explained simply
What the bargain element is, when AMT actually bites, and the 2026 exemption numbers.
Quick answers
Why is my RSU withholding wrong?
IRS rules let employers withhold a flat 22% on supplemental wages like RSU vests. But your actual marginal federal rate depends on total income — 24%, 32%, or 35% for many tech employees. The calculator shows the exact gap on your vest.
Will I owe AMT if I exercise my ISOs?
Maybe. The spread between your strike price and the fair market value at exercise is an AMT preference item. If it's large relative to your income, the tentative minimum tax can exceed your regular tax and you owe AMT. Run the ISO/AMT tab with your numbers.
What's a qualifying ESPP disposition?
You must sell more than 2 years after the offering date and more than 1 year after the purchase date. Miss either test and it's disqualifying — more of your gain is taxed as ordinary income.
Do I need to make quarterly estimated payments?
If your withholding won't cover the safe harbor — 100% of last year's total tax, or 110% if your AGI was over $150,000 — yes. The estimated-payment planner computes your target and per-quarter amounts.
Is my data sent anywhere?
The free calculator: no. Every calculation runs locally in your browser — no account, no tracking of your numbers. (If you use "Email my results," your results are transmitted once, only to email them to the address you enter.) VestWiz Pro is an account service and stores the data you save — see the privacy policy.