ISO vs. NSO FAQ
Last verified Oct 7, 2026 · Reviewed by Value8 valuation team
What's the actual difference between an ISO and an NSO?
An incentive stock option (ISO) can get favorable tax treatment (no regular tax at exercise, potential long-term capital gains on sale) if specific IRC Section 422 conditions are met, but can only be granted to employees and is capped at $100,000 of first-exercisable value per employee per calendar year. A non-qualified stock option (NSO) has none of those restrictions and can go to anyone, but the spread is taxed as ordinary income at exercise with no favorable alternative.
How is an NSO taxed at exercise?
The spread (fair market value at exercise minus the exercise price) is taxed as ordinary income in the year of exercise, subject to withholding and employment taxes for employees, regardless of whether the stock is sold. Gain or loss after exercise is a separate capital gain or loss event, measured from the exercise-date value.
How is an ISO taxed at exercise?
There is no regular income tax on the spread at exercise. The spread is instead an alternative minimum tax (AMT) preference item under IRC Section 56(b)(3), which can create an AMT liability in the exercise year even though no regular tax is due. If the shares are later sold in a qualifying disposition, the full gain from exercise price to sale price is long-term capital gain with no ordinary-income component.
What is the AMT preference item, and does it always create a tax bill?
It's the bargain element at ISO exercise (FMV at exercise minus exercise price), added back for alternative minimum tax purposes under IRC Section 56(b)(3). Whether it actually creates an AMT bill depends on the holder's full tax picture, including filing status, other income, and the AMT exemption phase-out, not a flat percentage of the spread; a holder with little other income and a small exercise may owe no AMT at all.
What is the ISO $100,000 limit?
IRC Section 422(d) caps the aggregate grant-date fair value of stock underlying ISOs that first become exercisable for one employee in any one calendar year at $100,000. It's a per-employee, per-calendar-year cap measured across all of that employee's ISO grants from the company, not a per-grant limit.
What happens to the portion of a grant over the $100,000 limit?
It's automatically treated as an NSO, not rejected. Treasury Regulation Section 1.422-4 requires the cap to be applied chronologically: options are counted in the order their shares first become exercisable, so the earliest-exercisable grants use up the $100,000 of ISO headroom first, and whatever amount would push the year's cumulative first-exercisable value over $100,000 gets NSO treatment for that excess portion.
What is a qualifying disposition?
A sale of ISO stock that occurs at least two years after the grant date and at least one year after the exercise date. A qualifying disposition taxes the entire gain from exercise price to sale price as long-term capital gain, with no ordinary income reported on the sale.
What is a disqualifying disposition?
A sale of ISO stock that fails either the two-year-from-grant or one-year-from-exercise holding period. A disqualifying disposition loses the ISO's favorable treatment on that sale: the bargain element at exercise (or the actual gain, if lower) becomes ordinary income in the year of the disqualifying sale, with any remaining gain taxed as capital gain.
What are the ISO holding period requirements?
Two years from the grant date and one year from the exercise date, both measured from the sale date. Both conditions must be met for a qualifying disposition; missing either one makes it a disqualifying disposition instead.
Who can receive ISOs, and who can receive NSOs?
ISOs can only go to employees of the company or a parent or subsidiary. NSOs can go to anyone: employees, advisors, consultants, contractors, and non-employee directors. A grant to a non-employee is an NSO by definition; it cannot qualify as an ISO regardless of its terms.
Is an ISO always better than an NSO for the recipient?
Not always. ISO treatment can produce a better outcome (capital gains instead of ordinary income on the spread) if the holder can hold through a qualifying disposition and absorb any AMT exposure in the exercise year. A holder who needs to sell shortly after exercise, who can't handle the exercise-year AMT bill, or who isn't eligible for ISOs in the first place (a non-employee, or an amount over the $100,000 cap) doesn't get that benefit, making the NSO outcome effectively equivalent or sometimes preferable for cash-flow timing.
Does a Section 83(b) election apply differently to ISOs vs. NSOs?
The election mechanics are the same for both: filing within 30 days of an early exercise locks in the tax measurement at exercise-date value instead of re-measuring as the stock vests. What differs is which tax event that locked-in value feeds: ordinary income for an NSO, the AMT preference item for an ISO.
Does Value8 track whether a grant is an ISO or an NSO?
Yes. The option type (ISO or NSO) is set on the equity plan or the individual grant at creation and is tracked as a first-class attribute of the award. See how Value8 handles ISO vs. NSO for how classification, the $100,000 check, and the related tax surfacing work in the product.
General information about ISO and NSO tax treatment under IRC Sections 421, 422, and 56(b)(3) and common practice, not legal or tax advice. Confirm specifics with your tax advisor or counsel.