Estimate the taxes withheld when your restricted stock units vest, spot the gap between what your employer withholds and what you likely owe, and model the capital gains tax if you sell.
Estimates only — not tax advice. State rates shown are supplemental/bonus withholding rates and may differ from your final state liability. Long-term capital gains are simplified to a flat 15% assumption; your actual rate (0%, 15%, or 20%) depends on total taxable income. Consult a CPA for your specific situation.
Restricted stock units are one of the most misunderstood pieces of tech and finance compensation, mostly because the tax hit arrives in two completely separate stages that feel like one event. Understanding the split is the single most useful thing you can do before your next vest date.
The moment your RSUs vest, the IRS treats the full fair market value of those shares as ordinary W-2 wages, exactly as if your employer had paid you a cash bonus and you used it to buy company stock on the open market. This happens automatically and is not optional or deferrable in the way a 401(k) contribution might be. If you have 500 shares vesting at $80 a share, that is $40,000 of ordinary income added to your W-2 for the year, regardless of what you decide to do with the shares afterward.
Because this is treated as supplemental wage income, employers do not withhold based on your actual W-4 or marginal bracket. Instead, the IRS mandates a flat federal supplemental withholding rate: 22% on the first $1 million of supplemental wages an employee receives in a calendar year, and 37% on anything above that threshold. This rule exists to simplify payroll processing, but it creates a very common problem for anyone whose true marginal federal bracket is above 22% — which includes most engineers, product managers, and finance professionals at companies large enough to grant meaningful RSU packages. If your marginal rate is 32%, 35%, or 37%, the 22% withheld at vest will not cover your eventual liability, and the difference becomes due when you file your return the following spring, often as an unpleasant surprise.
On top of federal income tax withholding, RSU vest income is also subject to FICA taxes just like any other wage. Social Security tax is 6.2%, but only applies up to the annual Social Security wage base — a dollar cap that resets each year and adjusts for inflation. If your salary alone already pushes you past that cap before your RSUs vest, you may owe no additional Social Security tax on the vest at all. Medicare tax, by contrast, is 1.45% with no cap whatsoever, so every dollar of vest income is subject to it. High earners also face the Additional Medicare Tax of 0.9% once combined wages for the year exceed $200,000 for single filers or $250,000 for married filing jointly — this additional tax specifically targets the marginal dollars above the threshold, so a large single vest that pushes you over the line will have part of it taxed at the higher combined Medicare rate.
Unlike federal supplemental withholding, which is a single nationwide flat rate, state supplemental withholding rates differ dramatically by jurisdiction. California withholds at 10.23% on supplemental wages including stock compensation, one of the highest rates in the country. New York withholds around 9.62%. States with no income tax at all — Texas, Florida, Washington, Nevada, and a handful of others — withhold nothing at the state level, which is one reason RSU-heavy compensation packages are especially valuable to employees based in those states. If you moved states during the vesting period, allocation between states can get genuinely complicated and is worth a conversation with a tax professional, particularly for mobile tech workers.
Once your shares vest and the ordinary income tax obligation is locked in, anything that happens to the stock price afterward is treated as a separate capital gain or loss, calculated against a cost basis equal to the fair market value at vest — not zero. This is the detail that trips up the most people: your cost basis is not what you "paid" (RSUs typically require no purchase price), it is the value that was already taxed as income at vest. If the stock is worth exactly what it was at vest when you sell, you have zero capital gain, because the income tax already captured that value.
If you sell within one year of the vest date, any gain above the vest-date value is taxed as a short-term capital gain, at your ordinary marginal income tax rate — the same bracket that applies to your salary. If you hold for more than one year past the vest date, the gain qualifies for long-term capital gains treatment, taxed at the more favorable 0%, 15%, or 20% federal rate depending on your total taxable income for the year. This is why many advisors distinguish clearly between the vest decision, which is not really a decision at all, and the sale-timing decision, which is a genuine investment choice with real tax consequences attached.
A common strategy, sometimes called "sell-to-cover" or "same-day sale," is to sell all or most vested shares immediately and diversify the proceeds into a broader portfolio. The logic is straightforward: you already owe ordinary income tax on the full vest value whether you sell or hold, so holding the shares is functionally the same as taking your after-tax bonus and voluntarily buying a concentrated position in your employer's stock. For most employees, having both their salary and a large slice of net worth tied to the same company's fortunes is a concentration risk worth avoiding, unless there is a specific, considered reason to hold — high conviction in continued appreciation, a long-term-gains timing strategy, or blackout-period restrictions on trading.
Consider an engineer earning a $180,000 base salary with a marginal federal bracket of 32%, who has 500 RSUs vest at $80 per share ($40,000 of income). Federal withholding at the mandatory 22% rate takes $8,800. But at a true 32% marginal rate, the actual federal liability on that $40,000 is closer to $12,800 — a shortfall of roughly $4,000 that will either need to be paid via estimated quarterly payments or will show up as a balance due when filing. Multiply this across two or three vest events a year, plus annual salary growth pushing someone into a higher bracket, and it becomes clear why so many RSU recipients are caught off guard by a tax bill each April despite having "already had taxes withheld" on their equity compensation.
The single most expensive mistake tech professionals make when selling vested Restricted Stock Units (RSUs) occurs during tax filing season on IRS Form 8949 and Schedule D.
When your RSUs vest, your company reports the Fair Market Value (FMV) as ordinary W-2 income in Box 1. You pay income tax on this value immediately upon vesting. Consequently, your cost basis in those shares becomes equal to that exact FMV at vest.
However, under IRS regulations updated in 2014, brokerages (such as E*TRADE, Schwab, Fidelity, or Shareworks) are strictly prohibited from reporting adjusted cost bases for non-covered securities on 1099-B forms.
Crucial Rule: Your adjusted cost basis per share equals the FMV on the date of vesting, NOT $0. If you sold shares immediately upon vesting via "Sell-to-Cover," your capital gain/loss should be virtually $0 (minus minor broker execution fees).
Federal tax law mandates that employers withhold a flat 22% supplemental wage tax rate on RSU income up to $1,000,000 (and 37% for amounts exceeding $1M). While this sounds convenient, it creates a massive surprise tax bill for high-earning software engineers and executives.
If your base salary puts you in the 32%, 35%, or 37% federal marginal tax bracket, a flat 22% withholding creates a 10% to 15% tax deficit on every single vested share.
| Federal Marginal Bracket | Statutory RSU Withholding | Tax Shortfall Per $100,000 Vested |
|---|---|---|
| 24% | 22% | $2,000 |
| 32% | 22% | $10,000 |
| 35% | 22% | $13,000 |
| 37% | 22% | $15,000 |
If your total tax shortfall exceeds $1,000 when filing, the IRS may assess underpayment penalties. To protect yourself, utilize one of the Safe Harbor Rules via quarterly estimated tax payments (Form 1040-ES):
With the rise of remote work and cross-state relocations (e.g., moving from California or New York to Texas, Washington, or Florida), RSU taxation becomes an intricate multi-state allocation puzzle.
RSU income is taxed by states based on the number of workdays performed within that state between the Grant Date and the Vesting Date, regardless of where you reside on the actual date of vest.
Many tech employees participate in an Employee Stock Purchase Plan (ESPP) or trade their company's stock in personal brokerage accounts while simultaneously vesting RSUs. This creates severe IRS Wash Sale Rule (Section 1091) risks.
A wash sale occurs when you sell stock at a capital loss and purchase "substantially identical" stock within a 61-day window (30 days before the sale, the day of the sale, or 30 days after the sale).
If you work at a private venture-backed startup, your RSUs operate under fundamentally different mechanics than public company shares.
Vest strictly on a time-based schedule (e.g., 4-year vest with a 1-year cliff).
Require two conditions to be met before shares actually vest and trigger tax liability:
Note on Section 83(b) Elections: You cannot file an 83(b) election on standard RSUs. 83(b) elections apply exclusively to Restricted Stock Awards (RSAs) or early-exercised stock options (NSOs/ISOs). Attempting to file an 83(b) for RSUs will be rejected by the IRS.
In Sell-to-Cover, your broker sells a portion of your newly vested shares on the open market to raise cash for tax withholding. In Net Withholding, your employer cancels a percentage of shares before issuing them, keeping them in treasury and paying the tax authority out of company funds. Both yield identical tax outcomes.
RSU income counts toward Medicare wages. Once your total combined W-2 earnings exceed $200,000 for single filers ($250,000 for married filing jointly), your employer must withhold an extra 0.9% Additional Medicare Tax on all income above that threshold.
Selling RSUs immediately upon vest does not incur additional capital gains taxes (since your cost basis equals the vest FMV). Holding shares means you are using your salary to invest in a single stock, exposing you to concentrated single-stock risk. Most financial planners recommend selling immediately and diversifying into low-cost index funds.
No, but it can look that way. RSUs are taxed once as ordinary income when they vest. If you hold the shares afterward and the price moves, that movement is taxed separately as a capital gain or loss — the original vest value is never taxed again.
The IRS mandates a flat 22% federal supplemental withholding rate on RSU income up to $1 million per year (37% above that), regardless of your actual marginal bracket. If your bracket is above 22%, you will likely owe the difference at filing time.
Sell-to-cover means your employer or brokerage automatically sells a portion of your newly vested shares to pay required withholding taxes, delivering the remaining shares to your account.
Yes. RSU income at vest is treated as regular wages for FICA and counts toward the annual Social Security wage base for that year.