How much tax do I owe when my RSUs vest?

An RSU vest is not an investment event. On the day the shares vest they are ordinary wage income, taxed exactly like salary, and they land in box 1 of your W-2 whether you sell a single share or not. Nothing about owning stock changes that. The only question is which rates the vest falls into, and the answer is: the ones sitting on top of everything else you earned that year.

So the honest way to price a vest is to run the year twice. At the inputs above, the return without the vest produces $32,267 of federal income tax. The same return with a $60,000 vest added produces $48,823. The vest cost $16,556, which is 27.6% of it. That is a measurement of two real returns, not a bracket rate multiplied by a number, and it is why the answer moves when your salary moves even though the vest does not.

Against that, your employer withheld $13,200. The gap is $3,356, and it is the entire subject of this page. Nobody sends you a bill for it. It does not appear on a statement from your broker or your equity administrator. It shows up once, in April, as a smaller refund or a larger balance due, mixed in with everything else on the return so that most people never work out where it came from.

Your employer is not guessing at your bracket. A vest is a supplemental wage payment, and IRS Publication 15 gives exactly one optional flat rate for supplemental wages: 22%, in the words "no other percentage allowed". That is a statutory number applied identically to every employee. It is not derived from your Form W-4, your salary, your filing status, or anything else about you.

Which means it is right for exactly one kind of person: someone whose marginal rate on the vest happens to be 22%. Everyone above that is short, and everyone below has lent the government money for free. At the inputs above, the next $100 of vest value is taxed at 32.0%, and the vest as a whole cost 27.6%, which is why $13,200 of withholding did not finish the job.

The rule bends in one place. Once supplemental wages for the calendar year pass $1,000,000, withholding on the excess becomes a mandatory 37%, regardless of your W-4. That counts bonuses and earlier vests, across businesses under common control, so a big year can cross the line without any one payment coming close to it. Even then it is a rate, not your rate: on a $1,200,000 vest at a $300,000 salary, $294,000 is withheld and the vest costs $437,158, leaving $143,158 outstanding.

This is the comparison worth running, and no RSU calculator on the open web will run it for you. Hold the vest fixed at $60,000 filing single, change only the salary it stacks on, and watch the withheld column refuse to move while the cost column climbs.

The crossing point is lower than almost anyone expects. For a $60,000 vest filing single, the flat rate stops covering the tax at $63,375 of salary. At $43,375 the withholding overshoots by $2,085; at $83,375 it is already $485 short. Below the line the number is a refund you had to wait for. Above it, it is a bill you did not know about.

The other direction is real too, and it gets ignored because it is the pleasant one. A $10,000 vest at a $60,000 salary costs $1,780, or 17.8%, while $2,200 was withheld on it. That is $420 of your money sitting with the IRS until you file, and 8 shares that were sold when they did not need to be.

Sell-to-cover is the default at most companies, and it does exactly what its name says: it sells enough shares to raise the withholding. It does not sell enough to cover the tax, because at the moment it runs nobody has computed the tax. At $50 a share, the $60,000 vest above is 1,200 shares, and 264 shares of them go to raise the $13,200 withheld.

Covering what the vest actually costs would take 331 shares. The difference is 67 shares, worth $3,356 at the vest price. Those shares are still in your account, which is the trap: the position looks like a gain and part of it is already spent. If the price falls between the vest and the day you pay, you sell more shares than 67 shares to raise the same money, and the tax does not fall with the stock. It was fixed on the vest date.

Some equity administrators let you elect to withhold extra shares, or to pay the withholding in cash instead of selling. Either one closes this gap at the vest instead of at filing, and either one is worth asking about before the next vest date rather than after it.

Federal income tax is pay-as-you-go. Underpaying through the year carries an interest charge under 26 U.S.C. § 6654 even if you settle the whole balance in April, and a vest is the most common way an ordinary salaried person trips it. The exemption is small: no estimated tax is required unless you expect to owe at least $1,000 for the year after withholding. At the inputs above the vest alone leaves $3,356 outstanding, which is well past it.

Two ways to close it, and they are not equivalent. An estimated payment counts from the quarter you send it, so a vest in the first quarter wants the April 15, 2025 installment and not the January 15, 2026 one. Extra withholding on your regular paycheck is treated as paid evenly across the whole year no matter when it happened, so raising it in the autumn can still cure a shortfall from a spring vest. If you have already missed an installment, the second route is usually the better one. There is also a safe harbor: paying 100% of last year's total tax through withholding and estimates, or 110% if last year's adjusted gross income was over $150,000, avoids the penalty however large this year's bill turns out to be.

One smaller gap rides along with the vest and is invisible on a pay stub. Your employer withholds the 0.9% Additional Medicare Tax above a flat $200,000 of wages, ignoring filing status, while your return applies it at your own threshold on Form 8959. The two disagree in both directions. On the same $60,000 vest and $180,000 salary, married filing jointly has $360 withheld on the vest and owes $0, so it comes back; married filing separately has the same $360 withheld and owes $540, leaving $180 more to pay. This calculator folds that into the estimated payment and reports it separately, so the number you send is the number that squares the vest.

State and local income tax. Your employer withholds separately for the state at its own supplemental rate, and that rate has the same problem as the federal one. Nine states charge no income tax at all; California, to pick the state most RSU holders live in, charges a supplemental rate well under its top marginal rate. Nothing on this page includes any of it, and for a large vest the state gap can be bigger than the federal one.

Social Security and regular Medicare. Both come out of the vest under their own rules and are not federal income tax. The only payroll item on this page is the Additional Medicare Tax, because it is the one that settles on Form 1040 rather than being final at withholding. If you are reconciling this against what actually hit your account on the vest date, ordinary payroll tax is most of the remaining difference.

What happens to the shares after the vest. The vest sets your cost basis at the same price it was taxed at, so selling on the vest date produces essentially no capital gain. Hold, and the difference from that price is a capital gain or loss this page does not compute. Watch your Form 1099-B: brokers frequently report a cost basis of zero on shares from a vest, and accepting that number means paying tax a second time on income already in box 1 of your W-2.

Everything else about the return. This assumes the standard deduction and wage income only, so itemized deductions, 401(k) and HSA contributions, dividends, interest, capital gains, and self-employment income all move the answer in ways not modeled here. It also assumes ordinary RSUs: incentive stock options, non-qualified options, an employee stock purchase plan, and a section 83(b) election on restricted stock are different rules entirely. The parameter set is tax year 2025 only, not a history of past brackets, and none of this is tax advice.

This calculator is built to be used without a browser. Every input is a query parameter on this page, and the same parameters on the JSON twin return the complete answer as a document.

GET /tools/rsu-tax.json?vest=60000&salary=180000&status=single

The response carries inputs after parsing and clamping, result with the federal income tax the vest adds and the rate that works out to, the flat supplemental withholding split into its 22% and 37% portions, the shortfall in dollars and in shares, the Additional Medicare Tax on both the return and the paycheck side, a measured marginal rate, and estimatedTax, the payment that closes the gap with its installment dates, plus sensitivity across a salary ladder and across all five filing statuses, drivers ranked by effect with a plain sentence each, assumptions that say for every field whether you supplied it and name the source when the default came from one, sources with a URL and an as-of date for each source the tool cites, which is an empty list on the calculators whose every default is an example input rather than a published figure, warnings, a disclaimer, and in tool the canonicalUrl and jsonUrl that carry only your non-default parameters. The canonical URL is the answer's permanent address; use it when you cite the number.

Parameters, all optional, in any order:

• vest ($), default $60,000.
• salary ($ per year), default $180,000 per year.
• price ($), default $50.
• other ($ per year), default $0 per year.
• priorSupplemental ($), default $0, from IRS Publication 15 (Circular E), Employer's Tax Guide, for use in 2025.
• status (one of single, married-joint, married-separate, head-of-household, qualifying-surviving-spouse), default single.

Values accept plain numbers and loose human formats such as 100k, $100,000, or 6.5%. Unknown parameters are ignored, values outside a field's range are clamped and reported in warnings, and the endpoint never fails on bad input. Responses are cacheable for a day; the defaults change when their sources publish, and tool.version changes when the method does.

• IRS Publication 15 (Circular E), Employer's Tax Guide, for use in 2025, as of 2025-01-01. Section 7 sets the flat 22% withholding on supplemental wages, in the words "no other percentage allowed", and sends supplemental wages above $1,000,000 for the year to a mandatory 37%. Section 15 sets the 0.9% Additional Medicare Tax an employer withholds above $200,000 of wages.
• Treas. Reg. § 31.3402(g)-1 (supplemental wage payments), as of 2025-01-01. The regulation the flat rate comes from, including the rule that the mandatory top rate applies to the excess over $1,000,000 of supplemental wages, counted across the whole calendar year and across businesses under common control.
• IRS Form 1040-ES, Estimated Tax for Individuals (2025), as of 2025-01-01. The installment dates and the safe harbor: no estimated tax is required unless you expect to owe at least $1,000 after withholding, and payments of 90% of this year's tax, or 100% of last year's (110% if last year's AGI was over $150,000), avoid the penalty.
• 26 U.S.C. § 6654 (failure to pay estimated income tax), as of 2025-01-01. The statute behind the underpayment penalty, its four installment dates, and the prior-year safe harbor the form describes.
• IRS Rev. Proc. 2024-40 (2025 inflation-adjusted items), as of 2025-01-01. The rate tables, standard deduction, and credit amounts for tax year 2025, as published by the IRS. One of the three parameter authorities the engine reports for every computation.
• One Big Beautiful Bill Act (P.L. 119-21), as of 2025-07-04. The statute that sets the current standard deduction and keeps the 37% top rate in place for 2025.
• 26 U.S.C. (Internal Revenue Code), as of 2025-01-01. The code sections the calculation implements: § 1 rates, § 63 deduction, § 83 property transferred for services, § 3101(b)(2) Additional Medicare Tax.

Two kinds of source, and the difference matters. The flat supplemental rate, the $1,000,000 line, the Additional Medicare Tax withholding threshold, and the estimated-tax rules are quoted from the IRS publications and the regulation that set them, because no return engine models what an employer withholds at the moment of payment. Everything on the tax side is computed by the engine, which reports its own parameter authorities for every computation rather than having citations attached after the fact.

Carlo is a personal finance agent. It knows your accounts, debts, and goals, so instead of a worked example at the vest you typed it can watch your actual pay and withholding through the year, notice the vest when it lands, and tell you what to set aside while there is still time to set it aside. Text it the question.

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