You hold incentive stock options (ISOs). The strike is low, the company is up, and exercising sounds straightforward. Then a parallel federal tax called Alternative Minimum Tax (AMT) shows up and changes the math. Four common traps decide whether your exercise is a free lever or a six-figure surprise. One of them is pure calendar timing.
AMT is a calendar-year trap. By the time April arrives, the decisions that moved your bill are already made.
The four most expensive AMT mistakes
AMT makes you yawn? The four below wake up anyone when they hit.
- Failing to plan the calendar of equity events. A January RSU vest, a mid-year ISO exercise, and a December stock bonus all in the same tax year compound: the vest and bonus push regular tax up, the exercise's bargain element pushes AMTI up further, and the bill arrives in April for a number that could have been much smaller in a different year. Same logic on a one-day scale: an exercise on December 30 versus January 2 lands in different tax years with potentially very different AMT bills. Always check what else falls in the same tax year before scheduling a large exercise; if your crossover is tight, deferring across the calendar boundary can dramatically lower total AMT.
- Ignoring state AMT. A single filer in California exercising a $50,000 bargain element pays roughly $13K of federal AMT plus $3.5K of California AMT: a 33% effective rate. Federal-only modeling underestimates the cost meaningfully in CA, MN, CO, and CT.
- Exercising without the cash to pay AMT. AMT is owed before April 15th, regardless of whether you sold any shares. If you exercise without selling, you owe AMT in cash on top of the strike price you already paid. Make sure the liquidity is there, or plan a same-year disqualifying disposition to fund the bill.
- Pushing past the income threshold where AMT relief gets clawed back. AMT applies a 26-28% rate to your AMT income (regular taxable income plus the ISO bargain element), minus an "exemption" that works like an AMT-specific standard deduction ($90K single / $140K MFJ for 2026). The 2025 One Big Beautiful Bill Act (OBBBA) tightened the phaseout above $500K single / $1M MFJ of AMT income: the exemption shrinks by 50 cents per extra dollar (pre-2026 was 25 cents at a higher threshold). A large exercise can push you well past the threshold and erode $20K-$40K of exemption that was protecting you. Spreading across years keeps it intact.
Each trap is worth a closer look once you have the underlying mechanics down. The rest of this article walks through how AMT actually charges you, how to find your own crossover, and how the multi-year credit eventually pays back most of what you owed.
What AMT actually charges you for
When you exercise an ISO, you pay the strike price and receive shares worth the current share price. The difference between those two is your bargain element, and it is your unrealized gain at exercise.
Regular tax does not care about the bargain element until you sell the shares. AMT does. The full bargain element gets added to your Alternative Minimum Taxable Income (AMTI) in the year you exercise, even if you never sell a share.
The AMT exemption and rates
AMT has its own version of the standard deduction. For tax year 2026, the AMT exemption is $90,100 for single filers and $140,200 for married filing jointly (inflation-adjusted from 2025's $88,100 / $137,000). AMTI below your exemption is not taxed. The One Big Beautiful Bill Act made these higher exemption levels permanent.
There is also a phaseout. The OBBBA (Section 70107) tightened it starting tax year 2026: the exemption shrinks by 50 cents for every dollar your AMTI exceeds $500,000 (single) or $1,000,000 (MFJ). Pre-2026, the rate was 25 cents per dollar starting at $626,350 / $1,252,700. For equity-rich tech employees, this means a large exercise can push you past lower thresholds and erode the exemption at twice the previous rate.
Your AMT crossover
Your AMT crossover is the largest exercise you can do in a single year before AMT starts adding tax on top of your regular bill. Below the crossover, AMT is zero (or small enough that your regular tax already covers it). Above the crossover, every additional ISO you exercise costs you 26-28% of the bargain element in extra federal tax, plus state AMT in four states.
Why this is the number that matters: ISOs are valuable specifically because their bargain element does not trigger ordinary income at exercise. Exercising up to your crossover preserves that benefit. Exercising above it gives part of the benefit back as AMT.
Your specific crossover depends on:
- Your salary and any other regular income
- Your filing status (single, married filing jointly)
- Other deductions and credits
- The strike price vs. the current share price
- Any state AMT you owe on top of federal
Why timing matters: the multi-year strategy
Here is the move that turns the crossover from a hard ceiling into a planning lever: it resets every January.
If exercising your whole stack in one year would push you well past the crossover, split the exercises across multiple tax years. Each year, exercise up to your crossover, pay zero (or minimal) AMT, and start the long-term capital-gains clock on those shares. The total bargain element does not change. But you stay in regular-tax territory for as much of it as possible.
The AMT credit (and how you get it back)
AMT is technically a prepayment, not a permanent tax. The portion of your AMT caused by deferral items (like an ISO exercise where you do not sell the shares that year) generates an AMT credit you carry forward to future years on Form 8801.
In any future year where your regular tax bill is higher than what AMT would have charged in that year, the credit pays you back. Selling some of those ISO shares as a qualifying disposition (held 2 years from grant and 1 year from exercise per IRS Topic 427, taxed at long-term capital gains) is one of the cleanest ways to spike regular tax above the AMT floor and unlock the credit.
Practically: a multi-year exercise plus hold plus sell plan can recover most of the AMT you paid, but only if the regular-tax-vs-AMT crossover flips in your favor in those later years. If your future regular tax stays low (extended career break, no qualifying dispositions), the credit sits unused on your return year after year. The AMT credit recovery deep dive walks the year-by-year mechanics with worked numbers.
State AMT can change the math
Four states currently have their own AMT that applies on top of federal AMT:
- California (7%): applies to most federal AMT preference items, including the ISO bargain element (FTB Schedule P)
- Colorado (3.47%): applies to Colorado AMTI in excess of the regular state tax base
- Connecticut (19% of federal AMT): piggybacks directly on the federal AMT computation
- Minnesota (6.75%): applies to the federal AMTI base with state adjustments per MN Statute 290.091 (MN DOR)
If you live in one of these states, your effective AMT rate on the bargain element runs roughly 29-35% (federal 26-28% plus state). That is enough to change which exercise size is worth doing in a given year. Most other states have no separate AMT; they had one historically and either repealed it (New York in 2014 per TSB-M-15(1)I, Wisconsin in 2019, Iowa in 2023) or never adopted one.
Where to go from here
For your specific numbers, the AMT + ISO Exercise Calculator computes your crossover, builds a multi-year exercise schedule, and tracks AMT credit recovery year by year. It also handles the 90-day post-termination exercise window (per IRC §422(a)(2)) with departure-date-aware planning.
If you also have NSOs, RSUs, or a concentrated single-stock position to think about, the NSO sell-vs-hold, RSU withholding gap, and concentration risk articles cover the adjacent decisions.
The calculators here handle one decision in isolation. OptionsAhoy plans the full picture jointly: every ISO, NSO, RSU vest, concentrated position, and hedge, across bullish, neutral, and bearish scenarios. The output is a year-by-year Plan optimized for total after-tax wealth. Free during beta.
Common questions
How do I figure out the AMT crossover point for exercising my ISOs?
The alternative minimum tax (AMT) crossover point is the largest incentive stock option (ISO) bargain element you can add in a year before your tentative minimum tax starts to exceed your regular tax. Below it, exercising costs no extra federal tax that year; above it, each additional share triggers AMT. You find it by computing your regular tax, then raising the ISO bargain element (shares times fair market value minus strike) until the two taxes meet. For a married-joint filer with $300,000 of income in California, the crossover is roughly $60,000 of bargain element in year one (here, about 699 shares at an $86 spread). The exact number depends on your income, state, and other AMT items; the calculator solves it for your inputs.
I have 50,000 vested ISOs with a $4 strike at $90 fair market value. Should I exercise all at once or split across multiple tax years?
Splitting beats a lump exercise here, and an optimized schedule beats an even split. Exercising all 50,000 at once front-loads a large alternative minimum tax (AMT) bill that you recover only slowly. For this position (married joint, $300,000 income, California, four-year horizon), the after-tax net final value is about $975,000 for a lump exercise, $988,000 for an even four-year split, and $1,261,000 for the optimized schedule, which exercises a small amount in the early years to bank AMT credit and the bulk once the shares qualify for long-term capital gains. The right split depends on your income, state, and price path; the calculator returns the optimized year-by-year plan.
Educational content for general information, not personalized tax, legal, or financial advice. Consult a qualified professional for your specific situation. See Terms.