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Capital Gains Tax on Stock Options

The tax treatment of stock options differs dramatically depending on the type: NSOs (non-qualified stock options) and ISOs (incentive stock options) each trigger ordinary income at exercise and then capital gains on the subsequent sale of the shares. But the timing of the ordinary income, the amount, and the alternative minimum tax exposure differ sharply—making the choice between NSO and ISO grants one of the most tax-loaded decisions in employee compensation.

Non-Qualified Stock Options (NSO): Immediate Ordinary Income

An NSO (also called NQSO) is the standard call option granted by a company to an employee, giving the right to buy the company’s stock at a fixed price (exercise price) for a set period (usually 10 years).

When you exercise an NSO—buy the shares by paying the exercise price—you immediately recognize ordinary income equal to the fair value of the shares minus the exercise price. This is ordinary income, taxed at your full marginal rate (up to 37% federal).

Example: You hold an NSO to buy 100 shares at $10 (exercise price). When you exercise, the stock is trading at $40. Your ordinary income at exercise is:

Stock fair value at exercise: 100 × $40 = $4,000
Less exercise price: 100 × $10 = $1,000
Ordinary income: $3,000

You owe income tax on $3,000 at your marginal rate. If your marginal rate is 37%, you owe $1,110 in federal income tax—at exercise, before you’ve sold a single share.

Your new cost basis in the 100 shares is $4,000 (the $1,000 you paid plus the $3,000 of ordinary income recognized).

The Capital Gain on Subsequent Sale

After exercise, you hold 100 shares with a basis of $4,000. Later, you sell them. Your capital gain or loss is:

Sale price − Basis

If you sell at $50 per share ($5,000 total), your capital gain is $5,000 − $4,000 = $1,000.

This $1,000 is a capital gain. If you held the shares more than one year from the exercise date, it’s a long-term capital gain, taxed at 0%, 15%, or 20% federal. If you sold within one year, it’s short-term, taxed at ordinary income rates.

So the total tax bill on an NSO exercise and sale is:

  • Ordinary income tax at exercise (on the spread)
  • Capital gains tax on the appreciation after exercise

This two-layer structure is the NSO tax trap: you pay tax on the spread even if the stock price later falls. If the stock drops to $30 after you exercise, you’ve still paid ordinary-income tax on the original $3,000 spread, and now you’re selling at a capital loss ($3,000 cost, $3,000 sale proceeds).

Incentive Stock Options (ISO): Deferred Ordinary Income & AMT

An ISO is a tax-favored option structure, only available to employees (not contractors or consultants). When you exercise an ISO, you do not recognize any ordinary income at exercise—a stark contrast to NSO.

The catch: ISOs trigger the alternative minimum tax (AMT). The spread at exercise (fair value minus exercise price) is added to your “alternative minimum taxable income” (AMTI). If your AMTI exceeds the AMT exemption, you owe AMT, which can be as high as 20% (when the spread is large).

For most people, especially in a bull market where the spread at exercise is steep, this AMT hit can be severe.

Example: You exercise an ISO to buy 100 shares at $10 (exercise price); stock is at $40. The spread is $3,000. This $3,000 is not ordinary income for federal income-tax purposes, but it is added to your alternative minimum taxable income.

If you’re already over the AMT exemption (roughly $87,500 for single filers in 2024, higher for married), you owe AMT of 20% × $3,000 = $600 on the spread without holding the shares yet.

If the stock later falls to $20 before you sell, you’ve paid $600 AMT on a spread that evaporated. This is the ISO trap: you pay AMT on unrealized gains.

The Qualifying Disposition: Long-Term Capital Gains Rates

If you satisfy the holding-period rules for a “qualifying disposition,” the entire gain on an ISO—including the spread at exercise—is treated as a long-term capital gain, taxed at the preferential 0%, 15%, or 20% rate.

Holding-period rules: You must hold the shares for at least 2 years from the grant date AND at least 1 year from the exercise date.

Example: You’re granted an ISO on January 1, 2024, with exercise price $10. You exercise on January 1, 2025, when the stock is $40 (spread $3,000, ordinary income $0, but AMT on $3,000). You sell on January 1, 2026 at $50. Your capital gain is:

Sale price: $5,000
Less exercise price: $1,000
Capital gain: $4,000

Because you held >2 years from grant and >1 year from exercise, this is a long-term capital gain. You owe $600 (AMT) + long-term capital gains tax on $4,000. If your long-term rate is 15%, you owe $600 (AMT) + $600 (cap gain) = $1,200 total.

Compare to NSO: You’d owe ordinary-income tax on the $3,000 spread (say, $1,110 at 37%) plus capital gains tax on the $1,000 appreciation after exercise ($150 at 15%) = $1,260 total. The ISO is slightly cheaper if you hit the qualifying disposition, but AMT is not always avoidable.

Non-Qualifying Disposition: Back to Ordinary Income

If you sell an ISO before satisfying the holding-period rules, it’s a non-qualifying disposition. The spread at exercise—which was deferred as not ordinary income at exercise—is now treated as ordinary income at the time of sale.

Example: Same as above, but you sell on July 1, 2025 (only 1.5 years from grant). You have a non-qualifying disposition.

At sale, you recognize:

  • Ordinary income: the spread = fair value at exercise ($40) minus exercise price ($10) = $30 per share = $3,000
  • Capital gain: the appreciation after exercise = sale price ($50) minus fair value at exercise ($40) = $10 per share = $1,000 (short-term capital gain, taxed at ordinary rates)

So you owe ordinary-income tax on $3,000 + short-term capital gain tax on $1,000 = ordinary-income tax on $4,000.

This is often worse than NSO. With NSO, you paid the ordinary income tax at exercise (deferring the capital gain until sale). With non-qualifying ISO, you pay it all at sale, and you get no preferential capital gains tax rate.

Practical Planning

ISO is favorable if:

  • You hold for the qualifying-disposition period (2 years from grant, 1 year from exercise)
  • The spread at exercise is moderate, so AMT is manageable or avoidable
  • You’re in a high tax bracket (ISOs defer tax to a year when you might be in a lower bracket, or when you’re no longer with the company)

NSO is favorable if:

  • The spread at exercise is enormous (ISO would trigger crushing AMT)
  • You plan to sell quickly (you avoid the holding-period trap)
  • You want certainty (no AMT surprise)

Wash-Sale Rules: The wash-sale rule applies to option exercises. If you exercise and sell within 30 days, or buy back the same stock within 30 days of a loss on option shares, you may be blocked from claiming a loss.

Reporting

See also

Wider context