When SpaceX rang the Nasdaq bell on June 12, 2026 — the largest IPO in history, closing its first day up 19% — it didn’t just mint headlines. It reminded thousands of tech employees that the paper value sitting in their equity grants is about to become a very real tax question. And for anyone holding incentive stock options, the most important part of that question isn’t the gain. It’s the alternative minimum tax.

I’ve spent a lot of years helping startup employees and executives navigate exactly this moment, and the same surprise comes up again and again: “I didn’t sell anything — why do I owe tax?” This guide answers that, and the rest of the ISO lifecycle, in plain English.

Three things to know before you read further

An ISO can turn ordinary income into capital gain — but only if you follow the rules. Incentive stock options are a special, statutory kind of stock option under Internal Revenue Code Section 422. Meet the requirements and the holding periods, and the entire gain can be taxed at lower long-term capital gains rates instead of as ordinary compensation.
The biggest practical issue is AMT, not regular tax. When you exercise an ISO, you usually owe nothing for regular income tax. But the “spread” between what you paid and what the shares are worth is an adjustment for the alternative minimum tax — so you can owe a real cash tax bill on stock you haven’t sold.
ISO planning is a three-way balancing act, and 2026 raised the stakes. Every decision trades off three things: preserving capital gains treatment, managing AMT exposure, and weighing what happens if you sell early. The One Big Beautiful Bill Act (OBBBA) accelerated the AMT phaseout starting in 2026, which makes a big exercise in an IPO year more likely to trigger AMT than it would have a year ago.

What is an incentive stock option (ISO)?

An incentive stock option is a stock option that meets a specific set of statutory requirements and, in exchange, qualifies for favorable federal income tax treatment. The rules live in two Code sections: Section 422 defines what an ISO is, and Section 421 governs how it’s taxed.

The payoff is the tax treatment. If you do everything right, you recognize no ordinary compensation income, and your profit is taxed as capital gain when you eventually sell. That’s meaningfully different from non-qualified stock options (NQSOs), where the spread at exercise is taxed as ordinary income right away.

The catch is the word “qualified.” An option labeled “ISO” in your equity plan only gets ISO treatment if it actually satisfies Section 422(b). The core requirements include:

It’s granted under a shareholder-approved plan that specifies how many shares are available and who’s eligible.
It’s granted within 10 years of the plan’s adoption or approval, and by its terms can’t be exercised more than 10 years after grant.
The exercise price is at least fair market value at grant.
It’s generally nontransferable except at death and exercisable only by you during your life.
If you own more than 10% of the company’s voting power, the price and term rules tighten (110% of fair market value and a five-year term).

There’s also a ceiling most people don’t realize exists.

The $100,000 rule

Under Section 422(d), only $100,000 of ISO stock can first become exercisable in any single calendar year. The $100,000 is measured by the fair market value at grant, and options are counted in the order they were granted. Anything above that line in a given year is automatically treated as a non-qualified option, no matter what your paperwork says. For employees at fast-growing companies with large grants, this quietly converts a chunk of “ISO” into NQSO treatment.

How are ISOs taxed at each stage?

ISOs have three moments that matter: grant, exercise, and sale. Two of them carry the real consequences.

Grant

Nothing happens at grant. Assuming the option is a valid ISO, receiving it is not a taxable event.

Exercise

Here’s where the two-track system kicks in.

For regular tax, if your option ultimately qualifies, Section 421(a) means you recognize no income when you exercise and receive the shares. Your employer also gets no compensation deduction.

For the alternative minimum tax, exercise usually does matter. The spread — fair market value at exercise minus what you paid — is reported as an AMT adjustment on Form 6251 (line 2i) in the year the shares become transferable and are no longer subject to a substantial risk of forfeiture. For most public-company employees, that’s simply the spread at exercise.

That spread also increases your AMT basis in the stock, which becomes important later. The result is that you can walk out of an exercise owing real tax on a gain you haven’t actually realized in cash.

Sale

Whether your sale is taxed as capital gain or partly as ordinary income depends entirely on whether you cleared the holding periods — which brings us to the rule that trips up the most people.

Qualifying vs. disqualifying disposition: the holding-period rules

To get full ISO treatment, Section 422(a)(1) requires you to clear both of these holding periods:

No sale within two years from the grant date, and
No sale within one year from the exercise date (when the shares were transferred to you).

Meet both, and you have a qualifying disposition: your entire gain, measured from the price you paid, is long-term capital gain.

Miss either one, and you have a disqualifying disposition. Under Section 421(b), the compensation income shifts into the year you sell. Generally, you recognize ordinary income equal to the spread at exercise, your employer gets a matching deduction, and any additional appreciation is capital gain.

There’s a useful taxpayer protection here. Under Section 422(c)(2), if you sell in a disqualifying disposition for less than the value at exercise (in a sale where a loss would be recognized), your ordinary income is capped at your actual economic gain — amount realized minus your basis. That cap matters a lot in a falling market, as the example below shows.

What is the “ISO AMT trap,” and did 2026 make it worse?

The AMT trap is the gap between paper gain and cash tax. You exercise, you hold (to start the capital gains clock), you sell nothing — and you still owe AMT on the spread. If the stock then drops before you sell, you can end up having paid tax on value that evaporated.

For 2026, the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly, up modestly from 2025. But the more important change is the phaseout. Under OBBBA, the exemption now begins to phase out at $500,000 (single) and $1,000,000 (married filing jointly) — down sharply from 2025 — and it phases out at 50 cents on the dollar, double the prior 25% rate. A married couple’s exemption is fully gone at roughly $1.28 million of AMT income, versus about $1.8 million under the old rules.

In practical terms: a large ISO exercise stacked on top of a strong income year — exactly the profile of someone at a newly public company — is more likely to land in AMT in 2026 than it would have been before. The rates didn’t change (still 26% and 28%), but losing the exemption faster effectively raises the bite.

The silver lining is that AMT is not a permanent extra tax. The AMT you pay on an ISO exercise often generates a minimum tax credit you can recover in later years, and your higher AMT basis reduces your AMT gain when you finally sell. It’s a timing problem and a cash-flow problem more than a permanent cost — but a six-figure timing problem is still a problem if you didn’t plan for it.

A 2026 ISO example, start to finish

Let’s make it concrete. Same facts across all three scenarios:

Your employer granted you an ISO on January 15, 2024 for 1,000 shares at $10.
You exercise all 1,000 shares on March 1, 2026, when the stock is worth $40.
You pay $10,000 to exercise. The shares are freely transferable and not forfeitable.

At exercise (2026): No regular-tax income. But your AMT adjustment is $40,000 − $10,000 = $30,000. Your regular-tax basis is $10,000; your AMT basis is $40,000.

Scenario A — Qualifying disposition (the goal)

You sell on April 1, 2027 at $50. You’re past two years from grant and one year from exercise, so this qualifies.

Long-term capital gain: $50,000 − $10,000 = $40,000
Employer deduction: none
Because your AMT basis was $40,000, your AMT gain is only $10,000 — reversing much of that earlier AMT adjustment.

This is the outcome ISO planning is built around: the whole $40,000 taxed at long-term capital gains rates.

Scenario B — Disqualifying disposition (sold too soon)

You instead sell on September 1, 2026 at $45. That’s inside the one-year window, so it’s disqualifying.

Ordinary compensation income: the $30,000 spread at exercise
Capital gain: $45,000 − $40,000 = $5,000
Employer deduction: $30,000
Because you exercised and sold in the same year, regular tax and AMT match — no separate AMT adjustment.

That last point is the underrated planning lever: a same-year exercise-and-sell sidesteps the AMT trap entirely, at the cost of capital gains treatment.

Scenario C — Disqualifying disposition at a loss (the market dropped)

Same disqualifying sale on September 1, 2026, but the stock has fallen to $25.

Section 422(c)(2) caps your ordinary income at your actual gain: $25,000 − $10,000 = $15,000, not the full $30,000 spread.

In a down market, that cap can be the difference between a manageable bill and a painful one.

What the SpaceX IPO means if you hold equity

A debut like SpaceX’s is the kind of event that turns equity planning from theoretical to urgent overnight. A few realities worth keeping front of mind:

An IPO doesn’t automatically create a taxable event for you — but it usually creates liquidity, and liquidity is what tempts people to exercise and sell on the same impulse. Slow down and run the numbers first.
Lockups change the math. If you’re restricted from selling for a period after the IPO, you may exercise (starting your holding-period clock and your AMT exposure) well before you can sell. That’s precisely the gap where the AMT trap bites.
Big liquidity years are AMT-sensitive years. With OBBBA’s faster 2026 phaseout, a windfall plus an ISO exercise is more likely to push you into AMT than the same moves would have last year.
Model the AMT before you click exercise. I can’t stress this enough. The single most common mistake I see is exercising in December, feeling good about avoiding ordinary income, and then getting an AMT bill in April with no plan to pay it.

This isn’t unique to SpaceX, of course — it applies to anyone at a company that just went public or is about to. But a marquee IPO is a useful reminder to dust off your grant documents.

Five things I tell clients before they exercise

Confirm you’re actually still eligible. Under Section 422(a)(2), you generally must remain an employee from grant until within three months before exercise (extended to one year if you’re disabled). People who leave and exercise later often unknowingly forfeit ISO treatment.
Check the $100,000 limit. Know how much of your grant is real ISO and how much spills into NQSO treatment.
Run the AMT projection. Estimate the spread, the AMT adjustment, and the cash you’d owe — ideally across this year and next.
Track two bases. Your regular-tax basis (usually the exercise price) and your AMT basis (exercise price plus the adjustment) are different, and that difference drives very different results when you sell.
Be careful with hedging. Some strategies to protect a concentrated position can be treated as a disposition and blow up your holding period. The treatment is nuanced — a purchased put is generally less problematic than a short-against-the-box position — so get advice before you hedge.

Frequently asked questions

Do I owe tax when my ISOs are granted? No. Grant is not a taxable event for a valid ISO.

Do I owe tax when I exercise an ISO? Usually not for regular income tax, thanks to Section 421(a). But the spread between fair market value and your exercise price is generally an AMT adjustment, which can create a real cash tax bill.

What’s the difference between a qualifying and disqualifying disposition? A qualifying disposition meets both holding periods — more than two years from grant and more than one year from exercise — and is taxed as capital gain. A disqualifying disposition misses one of them and triggers ordinary compensation income on the spread at exercise.

Can I avoid the AMT on my ISOs? Sometimes. Exercising and selling in the same year eliminates the AMT adjustment (but forfeits capital gains treatment). Other approaches include exercising smaller amounts each year to stay under the AMT threshold, or timing exercises in lower-income years. The right move depends on your full picture.

Is AMT money gone forever? Often not. AMT paid on an ISO exercise can generate a minimum tax credit usable in future years, and your higher AMT basis reduces AMT gain at sale. It’s largely a timing and cash-flow issue.

Does the SpaceX IPO change how my ISOs are taxed? No — the ISO rules are the same. What an IPO changes is your liquidity and your urgency, which is exactly why it’s worth planning before you exercise or sell.