Yes, employee stock options are taxable, but not at grant and not at vesting. Tax hits when you exercise the options or sell the resulting shares, and how much you owe depends on whether you hold non-qualified stock options (NSOs) or incentive stock options (ISOs). NSOs generate ordinary income at exercise, taxed at rates up to 37 percent for 2026. ISOs skip that immediate ordinary income tax but can trigger the Alternative Minimum Tax. Getting the difference right is often the difference between a routine tax year and a surprise five-figure bill.
Nothing Happens at Grant or Vesting
Receiving a stock option grant is not a taxable event. The IRS treats the grant as a promise of future equity, not a transfer of anything. Vesting isn’t taxable either. You’re earning the right to exercise, but no stock has changed hands and no money has moved. The clock on taxes starts when you actually exercise or sell.
How NSOs Are Taxed at Exercise
When you exercise a non-qualified stock option, the spread between your exercise price and the stock’s fair market value that day is treated as ordinary compensation income. Exercise price of $10, stock trading at $50, and you have $40 per share of ordinary income — the IRS treats it no differently than a cash bonus.1Office of the Law Revision Counsel. 26 USC 83 – Property Transferred in Connection with Performance of Services Your employer reports the spread on your W-2, and it’s taxed at your marginal rate. For 2026, the top rate is 37 percent, kicking in above $640,600 of taxable income for single filers.2Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
Social Security and Medicare taxes apply to the spread the same way they apply to regular wages. Because this counts as supplemental income, your employer withholds federal tax at a flat 22 percent (or 37 percent on any supplemental pay above $1 million in the year).3Internal Revenue Service. Publication 15 (2026), Employer’s Tax Guide If your marginal rate is higher than 22 percent, that withholding will fall short and you’ll owe more at filing.
How ISOs Are Taxed at Exercise
Exercising an incentive stock option produces no ordinary income under regular federal tax rules, provided you meet the ISO holding period requirements later on.4Office of the Law Revision Counsel. 26 USC 421 – General Rules No income tax, no payroll tax on the spread. That’s the point of an ISO.
The complication is the Alternative Minimum Tax. When calculating AMT liability, the ISO spread at exercise counts as an adjustment even though your regular tax return ignores it.5Office of the Law Revision Counsel. 26 USC 56 – Adjustments in Computing Alternative Minimum Taxable Income You compute tax under both systems and pay the higher one. A big ISO exercise, especially at a company whose stock has run up in value, is a classic AMT trigger.
The 2026 AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly, phasing out at $500,000 and $1,000,000 of AMT income.2Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 AMT is charged at 26 percent above the exemption, rising to 28 percent once excess income passes roughly $244,500.6Office of the Law Revision Counsel. 26 USC 55 – Alternative Minimum Tax Imposed
AMT paid because of an ISO exercise is not a permanent extra tax. It generates a credit you carry forward, and you can apply that credit in later years when your regular tax exceeds your AMT. Most people recover the full credit within a few years after selling the shares.
The $100,000 ISO Limit
Not every option labeled as an ISO stays one. ISOs carry a $100,000 annual limit measured by the fair market value of the stock at grant. If the total value of stock for which your ISOs first become exercisable in any calendar year exceeds $100,000, the excess is reclassified as NSOs — and taxed accordingly at exercise.7Office of the Law Revision Counsel. 26 USC 422 – Incentive Stock Options The IRS applies grants in the order issued.
An example: options granted on stock worth $25 per share, with 5,000 shares vesting in the same year. The first 4,000 shares ($100,000 worth) keep ISO treatment. The remaining 1,000 are treated as NSOs, with ordinary income and payroll tax on the spread when you exercise. Check your vesting schedule against this cap before you assume every option you hold is an ISO.
Capital Gains When You Sell
Selling the shares brings a second round of tax rules, and they run differently for each option type.
For shares acquired through NSO exercise, your cost basis is the fair market value on the exercise date, because you already paid ordinary income tax on the spread up to that value. Any further appreciation is a capital gain. Hold more than a year after exercise and you qualify for long-term capital gains rates of 0, 15, or 20 percent depending on your taxable income.8Internal Revenue Service. Topic No. 409, Capital Gains and Losses Sell within a year and the gain is taxed at ordinary rates.
For ISO shares, a qualifying sale requires holding the stock at least two years after the grant date and at least one year after the exercise date.7Office of the Law Revision Counsel. 26 USC 422 – Incentive Stock Options Meet both and your entire profit from exercise price to sale price is a long-term capital gain. For 2026, the 15 percent rate covers single filers with taxable income between roughly $49,450 and $545,500; above that, the rate is 20 percent.2Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
ISO Disqualifying Dispositions
Sell ISO shares before meeting both holding periods and the sale becomes a disqualifying disposition. The tax treatment reverts to NSO-like rules: the spread between exercise price and fair market value on the exercise date is reclassified as ordinary income and reported on your W-2. Any additional gain between exercise and sale keeps capital gain treatment.
There is one protective limit. If the stock dropped and you sold for less than its fair market value at exercise, the ordinary income is capped at your actual gain — the difference between sale price and exercise price. You will not be taxed on income you never received.
Selling a few days short of the one-year mark after exercise is one of the most expensive timing mistakes in this area. It swaps long-term capital gains treatment on the entire spread for ordinary income rates. If you are close to the deadline, waiting almost always wins the math.
The 3.8 Percent Net Investment Income Tax
Higher earners face one more layer. A 3.8 percent surtax applies to net investment income, including capital gains on stock sales, once your modified adjusted gross income exceeds $200,000 for single filers or $250,000 for married couples filing jointly.9Internal Revenue Service. Topic No. 559, Net Investment Income Tax These thresholds are not indexed for inflation.
Combined with the 20 percent long-term capital gains rate, the effective top rate on stock gains reaches 23.8 percent. A large ISO exercise followed by a same-year sale can push you past these thresholds even if your salary alone wouldn’t.
Early Exercise and the Section 83(b) Election
Some employers, particularly startups, allow you to exercise before your options vest. Under the default rule, you would not be taxed until the shares actually vested, because you could still forfeit them by leaving.1Office of the Law Revision Counsel. 26 USC 83 – Property Transferred in Connection with Performance of Services That means the taxable spread grows with the stock, and the full amount at each vesting date is ordinary income.
A Section 83(b) election changes the timing. By filing a written statement with the IRS within 30 days of exercise, you elect to recognize income now, based on the stock’s current value, instead of at each future vesting date. If the stock is worth pennies today and might be worth far more later, this converts future appreciation from ordinary income into long-term capital gain.
The risk is real. If the stock drops or you leave and forfeit the unvested shares, you paid tax on income you never received, with no refund. The election is irrevocable, and the 30-day filing window is absolute. Miss it by a day and the election is gone for that grant.
The Cost Basis Trap on Form 1099-B
When you sell shares, your brokerage issues Form 1099-B with the sale proceeds and reported cost basis.10Internal Revenue Service. About Form 1099-B, Proceeds from Broker and Barter Exchange Transactions This is where taxpayers most often overpay. Brokers frequently report cost basis as just the exercise price, ignoring the income you already recognized through your W-2 or an AMT adjustment. Filing without correcting that number on Form 8949 means paying tax on the same dollars twice.
For NSO shares, the correct cost basis is the fair market value on the exercise date, not the exercise price, because the spread was already taxed. For ISO shares in a qualifying sale, the cost basis is the exercise price (no ordinary income was recognized), but you’ll need to reconcile any AMT paid at exercise using the numbers from Form 3921, which your employer sends after any ISO exercise.11Internal Revenue Service. Instructions for Forms 3921 and 3922 Keep every grant date, exercise date, and exercise-date fair market value on file. Those dates also determine whether an ISO sale qualifies for long-term capital gain treatment in the first place.