ISO Exercise and AMT: What Happens in the Years After You Exercise

The scenario

You exercised incentive stock options (ISOs) in a private startup this year. The spread between your exercise price and the fair market value was large enough to trigger the Alternative Minimum Tax. Now you're holding the shares, planning to sell in two or three years, and wondering: do you owe AMT again next year? And the year after? Or was it a one-time event?

The short answer: AMT from an ISO exercise is triggered only in the year of exercise. You do not owe recurring AMT in subsequent years just for holding the shares. But the story doesn't end there — the AMT you paid generates a credit that you'll recover over time, and the eventual sale has its own tax mechanics that interact with your AMT history.

How ISOs create AMT liability

Under the regular tax system, exercising an ISO and holding the shares is a non-event — no income, no tax. But the AMT system treats the spread (FMV minus exercise price) as income in the year of exercise.

Suppose you exercise 10,000 ISOs with a $2 strike price when the 409A valuation is $12/share:

• Spread: ($12 − $2) × 10,000 = $100,000
• Regular tax: $0 (ISO exercise is not a taxable event for regular tax if you hold)
• AMT: $100,000 is added to your AMT income

The AMT calculation then runs in parallel with your regular tax. You compute your AMT liability and compare it to your regular tax. If AMT exceeds regular tax, you pay the difference as an additional tax.

For 2026, AMT rates are 26% on the first $239,100 of AMT income and 28% above that. The exemption amount is $90,100 (2026) for single filers. Under the OBBBA, the exemption phases out at a 50% rate beginning at $500,000 (2026) of AMT income for single filers — meaning for every $1 of AMT income above that threshold, you lose $0.50 of exemption.

In our example, the $100,000 spread might produce an additional AMT liability of roughly $18,000–$26,000, depending on your other income and deductions.

Year two and beyond: no recurring AMT

In the year after exercise, your AMT calculation resets. The ISO spread is not counted again. If you don't exercise more options and your regular income stays similar, your AMT and regular tax will likely be close to each other — and you'll owe no additional AMT.

The key principle: AMT from ISOs is an event-based tax, not a holding-based tax. The exercise creates the AMT income. Holding shares you already exercised does not generate new AMT income in subsequent years.

There is one nuance: if the shares you hold have appreciated further and you exercise additional ISOs in a later year, that new exercise creates new AMT income. But the old shares sitting in your brokerage generate nothing for AMT purposes.

The AMT credit: getting your money back

Here's the part most people miss. When you pay AMT because of ISO exercises, that AMT payment generates a minimum tax credit (MTC) that carries forward indefinitely.

The credit works like this: in any future year where your regular tax exceeds your tentative minimum tax, the difference can be offset by your accumulated MTC — up to the amount of the credit.

In practice, this means:

1. Year of exercise: You pay $20,000 in AMT above your regular tax. This creates a $20,000 MTC carryforward.
2. Following years: If your regular tax exceeds your tentative minimum tax by $5,000, you can use $5,000 of the credit, reducing your tax bill. You carry forward the remaining $15,000.
3. Year of sale: The sale often creates a large enough regular tax liability to absorb the entire remaining credit.

The MTC is reported on Form 8801 (Credit for Prior Year Minimum Tax). Many people forget to file this form and leave thousands of dollars on the table.

What happens when you sell: the dual-basis system

When you eventually sell ISO shares, the tax treatment depends on whether you meet the holding period requirements for a qualifying disposition:

• Hold the shares for at least 1 year after exercise
• Hold the shares for at least 2 years after the option grant date

Qualifying disposition (both holding periods met)

Your gain is calculated differently for regular tax and AMT:

• Regular tax basis: your exercise price ($2/share in our example)
• AMT basis: the FMV at exercise ($12/share)

If you sell at $25/share:

Your regular tax gain is $230,000. Your AMT gain is $130,000. Since the regular tax on $230,000 of LTCG far exceeds the AMT on $130,000, you'll owe no AMT — and your MTC from the exercise year will offset regular tax dollar-for-dollar.

This is the payback: the AMT you "overpaid" in the exercise year flows back to you as a credit in the sale year. You don't lose the money — you loaned it to the IRS interest-free.

Disqualifying disposition (holding period not met)

If you sell before meeting both holding periods, the spread at exercise (up to the amount of your actual gain) is taxed as ordinary income for regular tax. This usually means:

• Regular tax now recognizes the spread as income → regular tax rises
• AMT no longer sees a difference → AMT credit becomes usable sooner
• Net result: you pay ordinary income rates on the spread instead of capital gains rates

Disqualifying dispositions eliminate the AMT mismatch but at the cost of losing the preferential capital gains rate on the spread.

Worked example: exercise, hold 3 years, sell

Year 1 (Exercise):

• 10,000 shares, $2 strike, $12 FMV
• Spread: $100,000
• Regular income: $150,000 salary
• AMT addition: $100,000
• Additional AMT owed: ~$22,000
• MTC carryforward: $22,000

Year 2 (Hold):

• Regular income: $150,000 salary
• No AMT adjustment (shares are just sitting there)
• AMT owed: $0 additional
• MTC used: $3,000 (regular tax exceeds tentative minimum tax by that amount)
• MTC remaining: $19,000

Year 3 (Hold):

• Same as Year 2
• MTC used: $3,000
• MTC remaining: $16,000

Year 4 (Sell at $30/share):

• Regular tax LTCG: ($30 − $2) × 10,000 = $280,000 at 15–20% = $42,000–$56,000
• AMT LTCG: ($30 − $12) × 10,000 = $180,000
• Regular tax far exceeds AMT → all remaining $16,000 MTC is usable
• Net federal tax on sale: $42,000 − $16,000 = $26,000

Now total it up correctly. The mistake to avoid: the MTC you use is not an additional tax — it's a reduction of regular tax you already owe, so it must not be added back into the total. Across the four years you actually pay:

• AMT at exercise: $22,000
• Regular tax at sale, before credit: $42,000
• Less: total MTC recovered ($3,000 + $3,000 + $16,000 = $22,000): −$22,000

So your true cash outlay is $22,000 (AMT) + $42,000 (sale tax) − $22,000 (MTC recovered) = $42,000.

Seen another way: the entire $22,000 of AMT you paid at exercise comes back to you over time via the credit, so the net AMT cost attributable to the ISO is $0. The only tax that genuinely sticks is the long-term capital gains tax on the sale — $42,000 on $280,000 of gain, an effective rate of 15% (the LTCG rate), not 19.3%. The AMT was a timing event, not a permanent cost — an interest-free loan to the IRS that you recovered in full.

The liquidity trap: AMT on paper gains

The real danger with ISOs in private companies is paying AMT on shares you can't sell. If the company never goes public or the value drops, you've paid tax on phantom income.

Strategies to manage this:

• Exercise only what you can afford: calculate the AMT before exercising and ensure you have cash to cover it
• Same-year exercise and sell: if the company is public, a same-day sale is a disqualifying disposition but avoids the AMT/liquidity mismatch entirely
• Spread exercises across years: exercise a portion each year to keep AMT within manageable bounds and stay below the $500,000 (2026) exemption phase-out threshold
• 83(b) election on early-exercised ISOs: if your plan allows you to early-exercise unvested ISO shares (common in startups), you can — and generally should — file an 83(b) election within 30 days of exercise. It is a common myth that 83(b) "doesn't apply to ISOs." It does apply to early-exercised, still-unvested ISO shares: the election starts both the capital-gains holding-period clock and the ISO 2-year/1-year clocks at exercise, and it fixes the AMT measurement at the current (low) spread rather than letting it grow as the shares vest. Without an 83(b) election on unvested early-exercised shares, AMT income is instead measured at each vesting date on the then-current spread, which can be far larger.

State tax considerations

Most states conform to the federal AMT treatment, but several notable exceptions:

• California: has its own AMT with different rates (7%) and exemption amounts. California AMT from ISOs also generates a state MTC carryforward.
• New York: conforms to federal AMT treatment
• Texas, Florida, Washington, Nevada: no state income tax, so no state AMT concern

If you're in California, the combined federal + state AMT on a large ISO exercise can approach 33–35% of the spread — a significant cash outlay for shares you can't sell.

Key takeaways

AMT from an ISO exercise hits once, in the year of exercise. You don't owe recurring AMT for holding the shares. The AMT you pay generates a credit that you recover over subsequent years — and typically in full when you sell the shares in a qualifying disposition, which means the net AMT cost of a held-and-qualifying ISO is often $0 and the only tax that truly sticks is the long-term capital gains tax on the sale. The real risks are paying AMT on illiquid shares and failing to file Form 8801 to claim your credit in later years. And if you have the chance to early-exercise unvested shares, don't dismiss the 83(b) election — it can dramatically reduce your AMT exposure.