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How are ISOs taxed and what is the AMT trap?
Under the regular income tax, exercising incentive stock options triggers no tax. The alternative minimum tax still counts the spread between your strike price and that day's market value as income. Exercise and hold a big spread and you can owe tens of thousands of dollars on shares you have not sold. Hold two years from grant and one year from exercise and the whole gain is long term on your federal return.
Under the regular tax, nothing happens when you exercise.
An incentive stock option lets you buy company shares at a set price, the strike. If the stock is worth more than the strike on the day you exercise, the difference is the spread, also called the bargain element.
Under the regular income tax, the spread is not income. Nothing shows up on your W-2 and nothing is withheld. Hold the shares at least two years from the grant date and at least one year from the exercise date, and the whole gain, from the strike all the way up to the sale price, is a long term capital gain on your federal return. That deal is why ISOs look better than regular options.
A quick note on who is talking. opfinances.com is a licensed insurance agency. We are not a financial advisor, not a fiduciary, and not a tax adviser. This is general education, not advice about your situation.
The alternative minimum tax is a second return that counts the spread as income.
The AMT is a parallel calculation. You figure your tax the normal way, then figure it again with some deductions taken away and some income added back, and you pay whichever number is higher. The spread on ISOs you exercised and still hold at year end is one of the biggest add backs there is.
The second calculation has its own rates, 26% and 28%, after an exemption. For 2026 the exemption is 90,100 dollars single and 140,200 dollars married filing jointly. It shrinks by 50 cents for every dollar of AMT income over 500,000 single or 1,000,000 joint, so a large exercise can eat the exemption and raise the rate in the same year.
California runs its own AMT at a flat 7% with a smaller exemption, and it adds the spread back the same way. Your employer reports each exercise to you and to the IRS on Form 3921, so leaving the spread off your return is not an option.
The trap is paying real tax on a gain that only exists on paper.
Illustrative arithmetic, not a tax estimate. A Santa Clara couple earning 250,000 dollars in wages has 10,000 ISOs with a 2 dollar strike, and the stock is worth 22. They exercise in March for 20,000 dollars and hold, planning to wait a year for the long term rate. The spread is 200,000 dollars.
Their regular tax does not move. Their AMT calculation adds 200,000 dollars of income, and the extra federal tax comes to somewhere around 45,000 dollars, due the next April, before California adds its share. They have not sold a share or received a dollar.
Now the stock falls to 5. The shares are worth 50,000 dollars, and the tax bill is still based on 22. If the company is private, they may not be able to sell at any price. This happened to thousands of people in 2000 and 2001. They owed AMT on spreads that were gone by the time the bill arrived, some owed more than their shares had ever been worth, and Congress took years to pass relief.
You get a credit back for the AMT you paid, but slowly.
AMT paid because of an ISO exercise becomes a minimum tax credit, tracked on Form 8801, that you can use in a later year when your regular tax is higher than your AMT calculation. The shares also carry two cost bases from then on, the strike for the regular tax and the exercise day value for the AMT.
The catch is the word later. The credit only comes back in years when the regular tax is the higher number, and only by the size of the gap. Someone with a large credit and ordinary wages can take a decade to recover it.
Selling in the same year is the undo button, and it has a deadline.
Sell the shares before December 31 of the year you exercised and there is no AMT adjustment for that exercise. The spread, or the actual gain if the stock has dropped, is taxed as ordinary wages instead. That is a disqualifying disposition. You give up the long term rate on the spread, but you only pay tax on money you actually have.
So timing matters. Exercise in January and you have eleven months to watch the stock before deciding whether to hold through year end and accept the AMT, or sell and pay regular tax on a real gain. Exercise in December and you have days.
One more wrinkle. A disqualifying sale puts the ordinary income on your W-2, but your employer does not withhold tax on it. Set the money aside, because the bill comes in April either way.
Holding for the lower rate is a bet with your own money.
Holding gets you the gap between your ordinary federal rate and the long term rate, roughly 15 to 20 points on the spread for most households. California taxes the gain as ordinary income however long you held, up to 13.3%, so there is no state reward. The risk is the stock, the AMT bill, and having your paycheck and most of your net worth tied to one company.
For a large position that has already grown for years, there are structures that can change the tax on a sale. We are not going to list them, because which ones fit depends on facts only you have, and they are worth a real conversation before the sale rather than after.
About incentives. We get paid when a client ends up in a product we offer. Nobody gets paid when the answer is that you sold in the same year and kept it simple. Weigh anything anyone tells you about your options with that in mind, us included.
Before you decide
Questions worth asking.
What is the spread on the options I am thinking of exercising, and what would it add to my AMT income this year?
If I exercise and hold, how much federal and California AMT would I owe next April, and where does that cash come from?
If the stock falls by half after I exercise, what is my bill, and can I actually sell these shares to pay it?
How many years would it take me to recover the AMT credit at my normal income?
What do I save by holding for the long term rate compared with selling in the same year, in dollars, and how far can the stock drop before that saving is gone?
If you are recommending I exercise, hold, or move the proceeds into something, what do you earn on each choice?
Related
Are ISOs taxed when they are granted or when they vest?
No. Nothing is taxed at grant or at vesting. Tax starts at exercise under the AMT, and at sale under the regular tax.
What is the 100,000 dollar ISO limit?
Only 100,000 dollars of options, measured by the value of the shares on the grant date, can first become exercisable in any one calendar year and still count as ISOs. Anything above that is treated as a nonqualified option, which is taxed as wages at exercise.
Can I file an 83(b) election on ISOs?
Only if your company lets you exercise before the options vest. An 83(b) election then fixes the AMT spread at the early exercise date, when it is often small or zero. It does not apply to options you can only exercise after vesting.
Does the AMT credit ever expire?
No. The minimum tax credit carries forward until you use it. The limit is how fast you can use it, which depends on your regular tax exceeding your AMT calculation in later years.
Does California tax ISOs differently from the federal government?
California has its own AMT at 7% and adds the ISO spread back the same way, and it taxes the eventual gain as ordinary income at up to 13.3% no matter how long you held the shares.
Where this fits.
This question sits inside a bigger one. Tax Deferred Strategies walks through the whole decision rather than this one piece of it.
On Point Finances is a licensed insurance agency, not a tax, legal, or investment adviser. This page is general education, not a recommendation, and reading it does not create a client relationship.