ISO vs NSO: Which Stock Options Cost Your Team (and Your Cap Table) Less?

ISO vs NSO is the choice between incentive stock options, which only employees can get and which can qualify for long-term capital gains if the holding rules are met, and non-qualified stock options, which anyone can get but which are taxed as ordinary income on the spread the day they’re exercised. ISOs usually cost the employee less in tax, NSOs give the company a deduction and far more flexibility.

You’ll also see this written as incentive stock options vs non-qualified stock options, ISO vs NQSO, or statutory vs nonstatutory options. Same question. This isn’t tax or legal advice, and equity is one place where a startup lawyer and a CPA earn their fee, but here’s how the two actually work and where founders trip.

Why founders get stock options wrong

Most founders treat options like a sweetener. You can’t match the salary a big company offers, so you throw in “some equity” and move on. I understand the instinct. Equity feels free because no cash leaves the bank.

It isn’t free. Every option you grant is a slice of the company, and the type of option decides who pays tax, when they pay it, and whether your company gets a deduction. Pick the wrong one, or pick the right one and set it up badly, and your best early hire can end up with a tax bill on shares they can’t sell yet. That’s a fast way to turn a loyal employee into a bitter one.

So before you promise anybody a percentage, know which kind of paper you’re handing them.

ISO vs NSO at a glance

The rules above come from Internal Revenue Code section 422 and the IRS guide to stock options in Topic 427 and Publication 525, checked November 2026.

How incentive stock options are taxed

ISOs are the “statutory” kind, which means Congress wrote a specific rulebook for them. The IRS puts it plainly: with a statutory option “you generally don’t include any amount in your gross income when you receive or exercise the option. However, you may be subject to alternative minimum tax in the year you exercise an ISO” (IRS Topic 427).

Here’s the payoff. If the employee holds the shares at least two years from the grant date and at least one year from the exercise date, the whole gain, from strike price to sale price, can be taxed as long-term capital gain. That’s the reason people chase ISOs.

Break either holding period and it’s called a disqualifying disposition. Part of the gain gets treated as ordinary income, and at that point the company may get a deduction after all.

There are strings attached for the company too. Under section 422 the plan needs shareholder approval within 12 months, the strike price can’t be below fair market value on the grant date, and the option can’t run longer than ten years. Anyone who owns more than 10% of the voting stock needs a strike of at least 110% of fair market value and a five-year term. And the employee generally has to exercise within three months of leaving the job, or the option stops being an ISO.

The $100,000 ISO limit

This one catches people. If the stock behind the ISOs that become exercisable for the first time in a single year is worth more than $100,000, measured at the grant-date value, the excess is treated as an NSO. You don’t lose the options. Part of the grant just quietly changes type. With a big grant on a fast vesting schedule, that happens more often than founders expect.

The AMT trap nobody mentions in the offer letter

ISOs aren’t tax-free. They’re regular-tax-free at exercise. The spread between strike price and fair market value on exercise day goes into the alternative minimum tax calculation on Form 6251.

For 2026 the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly, and it starts phasing out at $500,000 and $1,000,000 of income (IRS, 2026 figures). Those numbers change, so check the current year before anyone exercises.

Picture an early engineer with a $1 strike price who exercises 40,000 options when the latest valuation says the shares are worth $11. That’s a $400,000 spread. No regular income tax that year, but a real chance of an AMT bill, paid in cash, on shares that still can’t be sold. If the company stalls, the shares might never be worth what the tax was calculated on.

That’s why I’d never let anyone on my team exercise a big ISO grant without running the AMT math first. Knowing the rule is one thing. Running your own numbers before you sign is what saves you.

How non-qualified stock options are taxed

NSOs (sometimes called NQSOs) are simpler and blunter. For most private-company NSOs, the IRS says “there’s no taxable event when the option is granted but you must include in income the fair market value of the stock received on exercise, less the amount paid, when you exercise the option” (IRS Topic 427).

That spread is ordinary income. For employees it’s treated as wages, so the company withholds income tax and Social Security and Medicare, and reports it on the W-2. For a contractor or advisor it goes on a 1099-NEC. After exercise, any further growth is capital gain or loss when the shares are sold.

The upside for the company is real. NSOs work for anyone, they have no $100,000 cap, and the company generally gets a deduction equal to the income the option holder reports, under section 83. That’s why advisors, board members and contractors almost always get NSOs. ISOs aren’t even an option for them.

Which stock options cost your team and your cap table less?

Here’s my honest take. Neither one is cheaper for the cap table. A share is a share. What changes is who carries the tax and when.

• For your employees: ISOs usually cost less, as long as they can afford to hold and they watch the AMT. For someone who can’t hold for a year after exercise, the advantage mostly disappears.
• For your company: NSOs usually cost less, because you get the deduction and you can grant them to anyone. The trade-off is payroll withholding at exercise.
• For your cap table: the type doesn’t change dilution. Grant size, vesting and how big a pool you set aside do.

Most venture-backed startups grant ISOs to employees and NSOs to everyone else. That’s a sensible default, not a law.

How to choose between ISOs and NSOs: a founder checklist

1. Get a 409A valuation first. ISOs need a strike price at or above fair market value, and NSOs priced below it can run into section 409A penalties. Get a 409A valuation done before you grant anything.
2. Sort people by type. Employees can get ISOs. Advisors, directors and contractors get NSOs.
3. Check the $100,000 line. For large grants, have counsel model how much of each grant becomes exercisable each year.
4. Decide on the exit window. ISOs revert after three months post-departure. Some companies offer longer exercise windows, which effectively converts those options to NSOs.
5. Explain the AMT in writing. A one-page memo with an example beats a surprise tax bill in April.
6. Send the forms on time. Form 3921 for ISO exercises, W-2 or 1099-NEC for NSO income.

And keep the founder conversation separate. Founders usually hold common stock outright, not options, so how you set the founder equity split is its own decision from how you build the employee pool.

Early exercise and what changes when you leave

Some startup plans let employees exercise before the options vest. That can make sense early, when the spread is close to zero, because a small spread means little or no AMT (for ISOs) or ordinary income (for NSOs). It’s paired with an 83(b) election, which has a hard 30-day deadline from the exercise date. Miss it and you can’t fix it.

Leaving is where ISOs quietly turn into NSOs. If the employee doesn’t exercise within three months after their last day, ISO treatment is gone (section 422 extends that to one year for disability). Anyone on your team who might leave should know the date before they hand in notice, not after.

My view is simple. Options are a promise. If you’re going to make that promise to someone who bet their career on you, take the hour to make sure the paper does what you told them it would.

FAQ: ISO vs NSO

Is an ISO or NSO better for employees?

ISOs are usually better for employees who can hold the shares two years from grant and one year from exercise, because the gain can be taxed as long-term capital gain. The catch is that the exercise spread can trigger alternative minimum tax.

Can contractors or advisors get ISOs?

No. ISOs can only go to employees. Contractors, advisors and outside directors receive NSOs, which are taxed as ordinary income on the spread when exercised.

Do NSOs get taxed twice?

Not on the same dollars. You pay ordinary income tax on the spread at exercise, which becomes your cost basis. Later, only growth above that basis is taxed as a capital gain when you sell.

What happens to ISOs if I leave the company?

You generally have three months after leaving to exercise and keep ISO status. After that, any options you still hold are treated as NSOs if the plan lets you exercise them at all.

What is the $100,000 ISO limit?

If the grant-date value of stock behind ISOs that first become exercisable in one calendar year exceeds $100,000, the excess is treated as NSOs. It applies per employee across all of the company’s ISO plans.

Do ISOs show up on a W-2?

Not when you exercise and hold. Your employer sends Form 3921 with the grant date, exercise date and values you need. Income only shows up as wages if you sell early in a disqualifying disposition.