How employee stock options work
A grant sets four things: the number of shares, the exercise (strike) price, a vesting schedule and an expiration date, often 10 years out. Once options vest, you can exercise them: pay the strike price, receive the shares and keep any value the market adds above that price. That difference between the market price and the strike price is the spread.
There are three common ways to exercise. You can pay cash and keep all the shares, sell them all at once in a cashless exercise, or sell just enough to cover the cost and taxes. At a private company there may be no market to sell into, so exercising means paying cash, and possibly tax, for shares you can’t yet sell.
Options are leveraged. When the stock is below the strike price, they are underwater: worthless to exercise, though they can recover before they expire. RSUs, by contrast, keep value as long as the shares do, and an employee stock purchase plan sells you discounted shares outright.
When employment ends, unvested options are usually forfeited, and vested ones must be exercised within a window your plan sets, often a few months. Missing it forfeits options that may be deep in the money, one reason large grants work as golden handcuffs.
How ISOs and NSOs are taxed
NSOs, also called nonqualified or nonstatutory options, are the default. You generally have no income at grant. At exercise, the spread is compensation: it appears in box 1 of your W-2 and in box 12 with code V, is subject to Social Security and Medicare tax, and has income tax withheld. Your cost basis in the shares becomes the strike price plus that income, and later price changes are capital gains or losses.
ISOs are statutory options with better regular-tax treatment. There is no income at grant or at exercise. If you keep the shares more than 2 years from the grant date and more than 1 year from exercise, the whole gain over the strike price is a long-term capital gain when you sell. Sell earlier and it is a disqualifying disposition: the spread at exercise, capped at your actual gain, becomes ordinary income, though without Social Security or Medicare tax.
The catch is the alternative minimum tax. The ISO spread counts as income for the AMT in the year your shares become transferable or vested, often the exercise date, unless you sell them in that same calendar year. Your employer sends Form 3921 for each ISO exercise with the dates and prices you need.
ISOs and the AMT in 2026
For 2026, the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly. It shrinks by 50 cents for each dollar of alternative minimum taxable income above $500,000 (single) or $1,000,000 (joint). AMT rates are 26%, then 28% above $244,500. You owe AMT only when this tentative minimum tax is higher than your regular tax, so the practical question is how much ISO spread fits under your regular tax bill in a given year. For a single filer with $200,000 of wages and the standard deduction, about $31,400 of spread fits in 2026 before any AMT is due.
A few tactics follow from the rules. Exercising in smaller lots over several years can keep each year’s spread under the AMT line. Exercising early in the calendar year leaves time to watch the stock: if it falls, selling before December 31 turns the exercise into a disqualifying disposition and removes the AMT adjustment. Exercising while the spread is small limits the adjustment altogether.
AMT paid because of ISOs isn’t always lost. It creates a minimum tax credit, claimed on Form 8801, that you can use in later years when your regular tax exceeds your tentative minimum tax. Keep records of your separate AMT basis, which includes the adjustment, because it differs from your regular-tax basis.
Rules an ISO must meet
Only options that meet section 422 of the tax code are ISOs. If a condition fails, the option, or the part of it that breaks a limit, is taxed as an NSO instead. Your grant agreement says which type you hold, and Form 3921 confirms each ISO exercise. Check these conditions before relying on ISO treatment in a tax plan, especially after a job change or a large new grant:
- Employees only: ISOs can go to employees, not to outside directors or contractors.
- Price and term: the strike must be at least the market value on the grant date, and the option can last no more than 10 years.
- Owners of more than 10% of the voting stock: the strike must be at least 110% of market value and the term no more than 5 years.
- $100,000 limit: options first exercisable in one calendar year for more than $100,000 of stock, valued at grant, are treated as NSOs above that amount.
- Leaving: exercise within 3 months after employment ends, or 1 year if you are disabled, to keep ISO treatment.
- Holding: sell more than 2 years after grant and 1 year after exercise for a qualifying disposition.
Common stock option mistakes
Option mistakes are costly because the deadlines are strict and the tax can arrive before any cash does. Most come down to three dates for each grant: when it vests, when your job ends and when it expires. Keep those dates on one calendar, and check them before you exercise, sell or resign. Your grant agreement, Form 3921 for ISO exercises and the broker’s Form 1099-B hold the figures you need at tax time.
- Letting vested options expire because the post-termination exercise window closed after you left.
- Exercising ISOs and holding the shares past December 31 without first estimating the AMT on the spread.
- Reporting the Form 1099-B basis unchanged. For options granted after 2013, it leaves out the income you reported at exercise, so add that amount on Form 8949.
- Missing the 30-day deadline for an 83(b) election after early-exercising unvested options.
- Holding exercised shares for a tax break until one company’s stock dominates your savings; a diversified portfolio limits that risk.
Illustrative numbers
Exercising 1,000 options at a $10 strike with the stock at $50
- market price at exercise
- the share’s fair market value on the day you exercise
- exercise price
- the fixed strike price set in your grant
- shares exercised
- the number of options you exercise
For NSOs the spread is wage income at exercise; for ISOs it is an AMT adjustment unless you sell in the same year.
Cash to exercise (1,000 × $10)$10,000
Spread at exercise$40,000
NSO: wages taxed at exercise$40,000
ISO: regular income at exercise / AMT adjustment$0 / $40,000
Later sale at $70, NSO shares held over a year$20,000 long-term gain
Later sale at $70, ISO holding periods met$60,000 long-term gain
Both paths are taxed on the same $60,000 of profit. The NSO puts $40,000 of it at ordinary rates plus payroll tax right away. The qualifying ISO moves all of it to long-term capital gains rates, in exchange for possible AMT in the exercise year and holding the shares more than a year after exercise and two years after grant.
At a glance
ISOs vs. NSOs at a glance (US federal tax)
| Question | Incentive stock options (ISOs) | Nonqualified stock options (NSOs) |
|---|---|---|
| Who can receive them | Employees only | Employees, directors, contractors and advisers |
| Tax at grant | None | Usually none |
| Regular tax at exercise | None | Spread taxed as wages |
| Social Security and Medicare | Not charged | Charged on the spread |
| Alternative minimum tax | Spread is an adjustment unless sold that year | No adjustment |
| Best-case sale | All gain long-term after 2 years from grant and 1 from exercise | Gain after exercise long-term after 1 year |
| Employer tax form | Form 3921 | W-2 box 12, code V |
| Annual limit | $100,000 first exercisable per year, valued at grant | None |
Put it in your plan
Stock options in MoneyWhatIf
MoneyWhatIf’s stock-grant section on a job’s income card models RSUs, and its guide states that it does not cover stock options, exercise prices, or an ISO bargain element for the AMT. Shares you already own from past exercises can be entered as a brokerage account with their balance and cost basis. The federal tax calculation runs the alternative minimum tax automatically, comparing it with the regular bill and adding only the excess, but an option exercise is not an input and the AMT credit carryforward is not fully modeled.
Common questions
Stock options FAQs
Do ISOs always trigger the AMT?
No. The spread is added to alternative minimum taxable income, but you owe AMT only if the resulting tentative minimum tax exceeds your regular tax. Smaller exercises often fit under that line. Selling the shares in the same calendar year removes the adjustment, and AMT caused by ISOs creates a credit you may recover in later years on Form 8801.
What happens to my stock options if I leave the company?
Unvested options are usually forfeited. Vested options must be exercised within the post-termination window in your plan, or they expire. ISOs also face a tax deadline: exercise more than 3 months after your employment ends, or more than 1 year if you are disabled, and the option is taxed as an NSO. Check both dates before you give notice, because they can differ.
Are employee stock options the same as call options?
Both give you the right to buy shares at a fixed price, but the similarity ends there. Exchange-traded calls are standardized contracts bought from other investors and can be sold at any time. Employee options are granted as pay, vest over time, usually can’t be sold or transferred (an ISO can pass only by will or inheritance) and may expire soon after you leave. Their spread is taxed as pay or under the ISO rules, while a traded call bought as an investment generally produces a capital gain or loss.
Can I make an 83(b) election on stock options?
Not on the option itself; IRS guidance says the election can’t be made for statutory or nonstatutory options. If your plan allows early exercise of unvested options, the shares you receive are restricted stock, and an 83(b) election filed within 30 days of that exercise can apply to them. It measures income at exercise, when the spread may be small or zero.
Should I exercise stock options before a company goes public?
It depends on cash, risk and tax. Exercising early can start the ISO holding clocks and lock in a smaller spread, but you pay the strike price, and possibly tax, for shares you can’t sell and that may lose value. Some people exercise only what they could afford to lose, weighing the AMT on ISOs or the wage tax on NSOs against the potential capital gains saving.