RSU Tax Calculator
When RSUs vest, the whole market value becomes ordinary income and your employer withholds at one flat supplemental rate that was never chosen for you. Enter the vest, the flat rate that was applied and your own marginal rate to see what the withholding actually covered and what is left to settle at filing.
Shares vesting 400 shares · Share price at vest $50 · Your other income this year $150,000 · +2 moreYour figuresEdit figures
The market price on the vest date — that price, not today's, sets the taxable amount
Salary and anything else, excluding this vest — it decides which band the vest lands in
The flat rate your employer withheld on the vest — 0 assumes nothing was withheld
The federal rate for the band your combined income falls in — look it up and enter it
Left to settle at filing
$20,000 is the gross value of the vest, and nothing past it is computed while your marginal rate is 0. Enter the federal rate for your band and the settlement fills in.
Example figures — replace them with your own.
- Gross value of the vest
- $20,000
- Your income including this vest
- $170,000
- Withheld at the flat rate
- $0
- Shares held back to cover it
- 0
- Shares you actually keep
- 400
- Value of the shares you keep
- $20,000
- Tax at your marginal rate
- $0
- Gap at filing, signed — above zero is still owed
- $0
- State withholding
- Not computed — this page is federal only
The right-hand column is empty until you enter a marginal rate — that is the lookup this page will not guess for you.
| Scenario | Flat supplemental withholding | At your marginal rate |
|---|---|---|
| Tax on this vest | $0 | $0 |
| Shares that would cover it | 0 | 0 |
| Value left after tax | $20,000 | $20,000 |
Method: Shares × price at vest = gross vest value; × the flat supplemental rate you supply = withheld; × the marginal rate you supply = tax at your rate; tax at your rate − withheld = the signed gap at filing, positive meaning still owed. Shares withheld are the ceiling of withheld ÷ price.
- NEITHER rate on this page carries a non-zero default, and neither was verified against a primary source — no such source was fetched into this repository. The flat supplemental withholding rate and the marginal rate are both values you look up and enter. Confirm them against current published material before relying on the result.
- While the marginal rate is 0 the page computes only as far as the GROSS VEST VALUE and states that no tax and no filing gap were computed. The headline in that state is the vest value, not a settlement. While the withholding rate is 0 the page assumes nothing was withheld, so the whole tax is shown as still owed and is knowingly HIGH.
- NO STATE WITHHOLDING IS COMPUTED. This page is federal only and a fixed breakdown row says so for every input, because state treatment of supplemental wages varies and no single primary document covers it. In the owing direction the real settlement is therefore larger than the figure shown.
- ONE marginal rate is applied to the WHOLE vest. That is exact only while the vest sits inside a single band; a vest that straddles a boundary is taxed partly at each rate, and this page will be high or low depending on which rate was entered. It is an approximation and is labelled as one wherever it appears.
- The gap is SIGNED and both directions are ordinary: positive is still owed, negative comes back. The headline shows the MAGNITUDE and the direction is stated in words, so money you owe is never read as money you are getting. The signed value itself is in the breakdown.
- Payroll taxes on the vest, deductions, credits, other withholding, and the capital gain or loss that accrues from the vest price onward are NOT modelled. The other-income field feeds the combined-income figure you use to pick a rate; it does not enter the tax arithmetic, because this page holds no bracket table.
No tax rates are used in this calculation.
This is an estimate, not financial or tax advice. Confirm figures with the linked source or a licensed professional before acting on them.
The flat withholding is a deposit, and it was sized for someone else
The moment restricted stock units vest, the market value of the vested shares becomes ordinary compensation. Not capital gains, not a future event, not something that waits until you sell: the full value on the vest date is wages, and it is taxed as wages. The shares you never asked to receive in cash are treated exactly as though your employer had paid you that amount and you had immediately bought stock with it. Everything that follows from that framing surprises people, and the surprises are almost always expensive in the same direction.
Because it is wages, your employer has to withhold. Because it is an irregular lump rather than a regular paycheque, it falls into the category payroll systems handle with a single flat percentage applied to everybody — the supplemental wage rate. That rate is not derived from your income, your filing status, your other withholding or anything else about you. It is one number, applied uniformly, and it was calibrated to be roughly adequate for a broad middle of the wage distribution. If your combined income for the year sits above that middle, the flat rate is structurally too low for you, and it is too low by an amount that grows with every dollar of income above the crossover.
The withholding usually happens in shares rather than in cash. Your employer holds back enough of the vesting shares to cover the flat-rate amount, sells them or retains them, and remits the proceeds. Whole shares only — a fraction of a share cannot be withheld — so the count is rounded up and the small excess is returned to you as cash. What lands in your brokerage account is the remainder. This is why the number of shares that appear is always smaller than the number that vested, and why the difference is not a fee.
None of that settles anything. The flat withholding is a deposit against a tax that nobody has computed yet, in precisely the way an estimated payment is. The actual tax on that vest income is whatever your own marginal rate takes from it, and that rate depends on your salary, your other income and where the vest lands once it is stacked on top of them. If your rate is higher than the flat rate — which is the whole reason this page exists — the difference is not withheld, not billed and not mentioned anywhere at the time. It appears months later, when a return is filed, and by then the shares are frequently sold, spent or held through a price drop.
So the useful question at vest is not "how much tax do I owe on this" but "how far did the withholding actually go". That is a subtraction with two rates in it, and this page does exactly that subtraction and nothing more: the value of the vest, the amount the flat rate held back, the amount your own marginal rate takes, and the signed difference between them. A positive difference is money to set aside now. A negative one is money that comes back, which is pleasant but also means a chunk of your compensation spent the year in someone else's account.
What this page deliberately does not know
Two of the fields on this page ship blank, and that is a decision rather than an oversight. The flat supplemental withholding rate and your marginal rate are both figures read off published material, and this repository states a rate as fact only when its primary source can be re-read automatically. No such source was fetched for either, so neither is asserted here. What the page does instead is refuse to compute past the point where the missing figure matters, and say so on screen.
While the marginal rate is 0, nothing beyond the gross value of the vest is computed. That restraint is load-bearing rather than tidy: with the rate at 0 the computed tax is 0, so the gap evaluates to the negative of the entire withholding, which would render as a large refund that was never calculated. A cold visitor would be told their withholding is coming back to them. The "not computed" state therefore outranks both directions, and the headline switches to the gross vest value, which is a figure the page genuinely knows.
The withholding rate is blank for a different reason, and the direction is the whole argument. Withholding is money already paid, so it only ever lowers the amount shown as still owed. A default there would understate the bill, and an understated bill is the expensive way to be wrong: you find out at filing, with the shares already sold. A zero overstates instead, which is recoverable, and the page says in as many words that the figure is deliberately high until the field is filled in.
Beyond the blanks, there is a longer list of things this calculation genuinely does not model. There is no state withholding here at all, and the breakdown carries a permanent row saying so — state treatment of supplemental wages varies and no single fetchable document covers it, so computing the federal part and silently omitting the state part would understate the bill without admitting it. Payroll taxes on the vest are not modelled either. Neither is the capital gain or loss that starts accruing the moment the shares land, measured from the vest price that became your basis. The page applies one marginal rate to the whole vest, which is right only while the vest sits inside a single band; a large vest that straddles two bands is taxed partly at each, and this page will overstate or understate depending on which rate you chose. And it assumes the price you enter is the price that set the taxable amount, which is the vest-date price, not today's.
What to do with the gap once you have it
A gap in either direction is a cash-flow fact before it is a tax fact, and the two directions call for different actions. If the figure says money is still owed, the useful response is to move that amount somewhere it cannot be spent, in the same week the shares land. The reason is specific to RSUs rather than general prudence: the shortfall is denominated in dollars but the asset you are holding against it is denominated in shares, and the shares can halve between vest and filing while the tax bill, which was fixed at the vest-date value, does not move at all. People who cover a shortfall by selling later are quietly betting on the share price for the privilege.
Selling enough shares at vest to cover the gap is the mechanically simplest fix, and it has a property worth naming: shares sold immediately at vest have almost no capital gain or loss, because the vest price became your basis moments earlier. Selling then is close to a non-event on the capital side, which is not true of selling six months in. The alternative — funding the gap from salary and keeping the shares — is a real choice, not a worse one, but it is a decision to increase your exposure to a single company whose stock you are already paid in. It is worth making that decision on purpose.
If the figure says money comes back, the action is smaller but not nothing. An over-withholding is an interest-free loan you did not choose to make, and if it recurs at every vest it is worth adjusting the rest of your withholding so that the year nets out closer to flat. That adjustment happens through your regular payroll withholding, not through the vest, because the flat supplemental rate is not something you can dial.
Either way, treat the output of this page as an estimate whose accuracy is bounded by the marginal rate you supplied. It applies one rate to the entire vest, it knows nothing about your deductions, credits, other withholding or state, and it does not know whether the vest pushed you across a band boundary. It is precise about the one thing it does compute — the distance between a flat rate and a rate you chose — and that distance is the number people are surprised by. Confirm the rates against current published material, and if the gap is large, confirm the whole picture with someone who can see your return.
Frequently asked questions
My RSUs vested and I did not sell anything. Do I owe tax already?
Yes. Vesting is the taxable event, not selling. On the day the units vest, the market value of the shares becomes ordinary compensation income and is taxed as wages, exactly as though your employer had paid you that amount in cash. Selling later is a separate event that produces a capital gain or loss measured from the vest-date price, which became your cost basis. That is why the tax on a vest can be due in a year when you received no cash at all, and why holding the shares does not postpone anything.
Why did fewer shares appear in my account than vested?
Because your employer withheld tax in shares rather than in cash. It calculates the flat supplemental withholding on the full vest value, holds back enough shares to cover that amount, and remits the proceeds as your withholding. Shares cannot be split, so the count is rounded up and the small excess is normally returned to you as cash. The missing shares are not a fee and not a company deduction — they are your tax payment, and they will appear as withholding on your wage statement.
Why is the withholding rate field blank instead of pre-filled?
Because this page does not state a rate it has not verified against a primary source, and no such source was fetched into this repository. There is a second reason specific to this field: withholding is money already paid, so any value here lowers the amount shown as still owed. A pre-filled rate would understate your bill, and you would discover that at filing with the shares already sold. Zero overstates instead, which is the recoverable direction, and the page says on screen that the figure is deliberately high until you fill the field in.
Why does the page show nothing until I enter a marginal rate?
Because a marginal rate is a table lookup, and there is no neutral default for a lookup — any number would assert a band you may not be in. It also matters mechanically. With the rate at zero the computed tax is zero, so the gap would evaluate to the negative of your entire withholding and display as a large refund that was never calculated. Rather than show that, the page stops at the gross vest value, keeps the headline on a figure it actually knows, and states that no tax and no gap were computed.
The result says I still owe money. Is the calculator wrong?
Probably not. Owing more at filing is the ordinary outcome for anyone whose combined income sits above the band the flat supplemental rate was designed around, because that single rate is applied to everyone regardless of income. The higher your own marginal rate, the further the flat withholding falls short, and the shortfall grows with every dollar above the crossover. Check that you entered the rate for the band your income including the vest falls into, and remember this figure covers federal tax only.
Does this include state tax?
No. This page is federal only, and the result table carries a permanent row saying so rather than leaving you to infer it. State treatment of supplemental wages varies, there is no single fetchable document that covers every state, and computing the federal part while silently omitting the state part would understate your bill without admitting it. If your state taxes wage income, your actual settlement will be larger than the figure here in the owing direction, so treat this as a floor rather than a total.