What Is Personal FinanceEmployee stock options and restricted stock units (RSUs) both tie part of your compensation to company stock, but they work in different enough ways that treating them the same leads to costly mistakes. This guide assumes the basics from investing basics for beginners and focuses on what makes equity compensation different from a regular paycheck.
Stock options: the right to buy, not the stock itself
A stock option grants the right to buy a set number of shares at a fixed price, called the strike price, for a set period after it vests. If the stock trades above the strike price, exercising the option (paying the strike price to own the shares outright) locks in a gain equal to the difference. If the stock trades below the strike price, exercising makes no sense, since you'd pay more than the shares are worth on the open market. In that case the option sits worthless until the stock recovers or the option expires.
Two common structures show up at US companies: incentive stock options (ISOs) and non-qualified stock options (NSOs). Both work on the strike-price mechanic above. The difference sits in tax treatment. ISOs qualify for more favorable tax treatment under certain holding-period conditions, while NSOs get taxed as ordinary income at exercise, a detail worth confirming with a tax professional rather than assuming from a general guide, since the rules carry real dollar consequences and change over time.
RSUs: shares granted, not purchased
A restricted stock unit is a promise from the employer to give you actual shares once a vesting condition is met, usually the passage of time. Unlike an option, an RSU doesn't require you to pay anything to receive the shares. Once it vests, the shares land in your account and get taxed as ordinary income based on their fair market value at that moment, similar to a cash bonus paid in stock instead of dollars. Your employer typically withholds part of the shares or requires a separate withholding payment to cover that tax bill.
The difference that trips people up most
Here's the core distinction employees confuse: an option is worthless if the stock price drops below the strike price, because paying more than market value to exercise makes no financial sense. An RSU holds value as long as the stock has any value at all, since you never paid for the shares in the first place. A company whose stock falls 50% leaves option holders with sharply reduced or zero paper value. RSU holders in the same company still hold something worth half of what it used to be. That asymmetry matters when you evaluate job offers or weigh the standard "total compensation" number a recruiter quotes, since options and RSUs of the same headline value carry different risk.
Vesting schedules
Both options and RSUs usually vest over time rather than arriving all at once. A common structure at many US tech companies grants equity over four years with a one-year cliff, meaning nothing vests until you've worked there for a full year, at which point a chunk vests at once and the rest vests monthly or quarterly after that. This is an illustrative common pattern, not a universal rule. Some companies front-load vesting, others spread it evenly, and startups sometimes attach vesting to a liquidity event like an acquisition or IPO instead of a plain calendar.
Concentration risk: your paycheck and your portfolio, same company
Equity compensation ties two things to the fate of a single company: your job and part of your investment portfolio. If the company struggles, you risk a layoff and a falling stock value at the same time, a correlation an outside investor never takes on. Once shares vest and the tax bill is paid, selling some or all of that stock and reinvesting the proceeds into a diversified portfolio reduces that overlap. See what is diversification for why spreading holdings across many companies matters, and weigh that against any personal conviction about your own employer's prospects, since that conviction is worth questioning given how much you already have riding on the same outcome.
Nothing here recommends exercising, holding, or selling any specific equity grant. Equity compensation involves genuine tax complexity that depends on your specific grant type, timing, and jurisdiction. Talk to a tax professional before making exercise or sale decisions.