Exercising ISOs without an AMT surprise
Exercising incentive stock options feels like a non-event: no regular income tax, shares land in your account, done. Then April arrives with an Alternative Minimum Tax bill nobody warned you about. Every item below is a real planning lever — run through them before you exercise, not after. Start with the ISO/AMT estimator to size your exposure.
1. Know the $100,000 annual limit
Only $100,000 of grant-date value in ISOs can first become exercisable in any calendar year. Anything above that is automatically reclassified as non-qualified stock options (NSOs) — which are taxed like RSUs at exercise, as ordinary income. If you hold a large grant, part of it may already be NSOs without you realizing. Check your grant details before assuming ISO treatment.
2. Spread exercises across calendar years
AMT exposure is measured per tax year. Exercising everything in one December can blow past the $90,100 (single) / $140,200 (married) AMT exemption and into the phase-out zone, while splitting the same exercise across two or three Januarys keeps each year's AMT income lower. Multi-year spreading is the highest-leverage AMT planning move most employees have — and it costs nothing but patience.
3. Exercise early in the year when you can
A January exercise gives you an escape hatch a December exercise doesn't: if the stock drops during the year, you can sell before December 31 in a disqualifying disposition, which generally eliminates the AMT on that exercise (the spread disappears because you no longer hold the shares). Exercising in December gives you no time to react. Early-year exercises also start your one-year holding clock sooner for qualifying-disposition treatment.
4. Respect the 90-day clock after leaving
Standard ISO terms give you just 90 days after termination to exercise vested options — then they're gone. (Some companies extend this; most don't.) Leaving a job starts a countdown that forces an exercise decision on a deadline, often with AMT consequences you haven't modeled. If a departure is on the horizon, model the exercise now.
5. Private-company ISOs: the paper-tax trap
The most dangerous ISO scenario: exercising at a private company where the 409A valuation creates a large bargain element, generating AMT on shares you cannot sell. Employees have paid six-figure tax bills on illiquid stock that later became worthless. If your company is private, treat every exercise as a cash-flow decision first (strike price + potential AMT, out of pocket, with no sale proceeds) and a tax decision second.
6. Early exercise + 83(b) can lock in a low spread
If your company allows exercising unvested options, filing an 83(b) election within 30 days taxes the spread at today's (usually tiny) value instead of the value at each future vest date. It's a powerful move at early-stage startups — and completely unavailable once the shares have vested.