Incentive stock options (ISOs) can convert your entire option gain into long-term capital gain, but only if you navigate holding periods and the alternative minimum tax. Non-qualified stock options (NSOs) are simpler: you pay ordinary income tax when you exercise, and that is the end of the complexity. The right choice at exercise time depends on your cash, your AMT exposure, and how long you can hold the shares.

What is the core tax difference?

With an NSO, the tax event is exercise. You pay ordinary income tax on the spread between the strike price and the fair market value that day, your employer withholds on it, and your basis in the shares steps up to the market value. Any later appreciation is capital gain or loss (IRS Topic 427).

With an ISO, there is no regular income tax at exercise. Instead, the spread is added to your income for alternative minimum tax purposes in the exercise year. If you then hold the shares until you have satisfied both holding periods, more than two years after the grant date and more than one year after the exercise date, the entire gain is long-term capital gain when you sell (IRS Topic 427, IRC Section 422).

In short: NSOs tax you now at ordinary rates with no surprises later. ISOs defer the tax and offer capital-gain rates, but charge you complexity and AMT risk for the privilege.

How does the ISO AMT adjustment work?

Illustrative example: you exercise 1,000 ISOs with a $10 strike price when the fair market value is $50. The $40,000 spread ($50 minus $10, times 1,000 shares) is added to your alternative minimum taxable income for that year. You owe no regular income tax on the exercise, but that $40,000 can push you into AMT.

Whether AMT actually bites depends on your whole return. For 2026, the AMT exemption is $90,100 for single filers and $140,200 for joint filers, phasing out above $500,000 and $1,000,000 of AMT income. AMT rates are 26% and 28%, with the 28% rate applying above $244,500 of AMT base in 2026 (Rev. Proc. 2025-32). AMT you pay because of ISO exercises is not lost money: it generally creates a minimum tax credit you carry forward and use against regular tax in future years (IRS Instructions for Form 6251).

The nightmare scenario is exercising ISOs, holding the shares for the qualifying disposition, watching the stock crater, and still owing AMT on the higher exercise-date value. The AMT credit softens this over time, but it does not eliminate the cash-flow pain in the exercise year. Never exercise ISOs for the maximum qualifying benefit without modeling the AMT first.

What is a disqualifying disposition?

Sell ISO shares before meeting both holding periods and you trigger a disqualifying disposition. The bargain element at exercise, the spread between market value and strike price on exercise day, is recharacterized as ordinary income (capped at your actual gain if you sold for less than the exercise-day value). Only appreciation beyond that is capital gain. Your basis adjusts upward by the ordinary income recognized, so you are not taxed twice (IRC Section 422, IRS Topic 427).

A disqualifying disposition is not a penalty; it just converts the ISO into roughly NSO-like treatment for the bargain element. Sometimes it is deliberate: if you need the cash or the AMT on a qualifying hold would be brutal, selling early and paying ordinary income on the spread can be the rational move.

What are the structural differences?

The $100,000 limit deserves emphasis because it surprises people at exercise time. It is measured on grant-date value of shares first exercisable in a calendar year, across all your employer's plans. If your grants exceed it, the excess is simply treated as an NSO: ordinary income at exercise, no AMT wrinkle, no holding-period game (IRC Section 422(d)).

When is each one better?

ISOs win when you have the cash to exercise without selling, you can model and absorb the AMT (or your spread is small enough to stay under the exemption), and you can hold through both holding periods. The payoff is the full spread taxed at long-term capital gains rates instead of ordinary rates.

NSOs win when you want simplicity and certainty: exercise, pay the tax, move on. There is no AMT exposure, no holding-period calendar to manage, and no risk of a disqualifying disposition because the ordinary income is settled at exercise by design. For contractors and advisors, NSOs are the only game in town anyway.

A same-day sale of ISOs (exercise and sell immediately) is effectively NSO treatment: the bargain element is ordinary income, reported on your W-2. People do this to capture the spread without AMT or holding risk, which is rational when the stock is volatile or the AMT modeling looks ugly.

Updated October 14, 2026.

This article is free educational content, not tax advice for your specific situation. If you want a plan built around your actual numbers, that is what our paid tax planning engagements do.