Want the full ISO mechanics, qualifying vs disqualifying disposition rules, and the ISO-vs-NSO decision logic? Read the companion guide.
Read the ISO vs NSO Guide →
Short Answer
An incentive stock option exercise creates an AMT preference under IRC §56(b)(3) equal to the bargain element - (FMV at exercise minus exercise price) times shares - if you hold past December 31 of the exercise year. For regular tax there is no event at exercise; the spread becomes long-term capital gain on sale if you hold two years from grant and one year from exercise (the §422 qualifying disposition test). For AMT, the bargain element is added to AMTI, the §55 exemption is applied with the OBBBA 50 percent phase-out, and the 26 / 28 percent rates produce the tentative minimum tax. AMT owed equals max(TMT minus regular tax, zero). A same-year disqualifying disposition reverses the preference - the spread becomes ordinary W-2 wages, no AMT, but you give up the long-term capital gain rate on future appreciation.
Key Takeaways
- Bargain element = (FMV at exercise - strike price) × shares. Reported on Form 3921 boxes 3, 4, and 5.
- Hold-past-year-end path: bargain element is an AMT preference under §56(b)(3); no regular-tax event; LTCG on sale if §422 holding tests met (2 years from grant + 1 year from exercise).
- Same-year sell path: disqualifying disposition. Bargain element becomes ordinary W-2 wages. No AMT preference. No LTCG rate on the spread - only on appreciation above the FMV at exercise (rare in same-year sales).
- 2026 AMT exemption: 90,100 dollars single / HOH, 140,200 dollars MFJ / QSS, 70,100 dollars MFS (Rev. Proc. 2025-32).
- 2026 phase-out doubles to 50% of AMTI above 500,000 dollars (single / HOH / MFS) or 1,000,000 dollars (MFJ) under OBBBA §70107 - meaningfully expands AMT exposure for ISO exercisers.
- AMT crossover = largest bargain element your inputs allow before TMT exceeds regular tax. Below crossover: no AMT cash. Above: 26-42% marginal AMT depending on phase-out band.
- AMT basis (FMV at exercise) is higher than regular-tax basis (strike). Reverses on sale - reduces future TMT and unlocks Form 8801 minimum tax credit.
How This Calculator Works
Step 1 - Compute the bargain element
Bargain element = (FMV at exercise - strike price) × shares. This is the dollar amount transferred from your employer to you on the exercise date. Form 3921 box 4 reports the FMV per share, box 3 reports the strike, and box 5 reports the share count. The bargain element flows to Form 6251 line 2i if you hold past December 31, or to Form W-2 box 1 wages if you sell same-year.
Step 2 - Build AMTI (hold path)
If holding past year-end: AMTI = regular taxable income + standard deduction add-back (if std ded) + SALT add-back + bargain element. If selling same-year: AMTI = regular taxable income + (bargain element added to W-2 wages, which is already included in regular taxable income) + standard deduction add-back + SALT add-back. The same-year path has no separate AMT bargain element preference because the spread is regular-tax W-2 wages.
Step 3 - Apply the AMT exemption with phase-out
The 2026 base exemption is 90,100 dollars single / HOH, 140,200 dollars MFJ, 70,100 dollars MFS. Reduced exemption = max(0, base - 0.50 × (AMTI - threshold)) where the threshold is 500,000 single / HOH / MFS or 1,000,000 MFJ for 2026. Exemption fully gone at AMTI of 680,200 / 1,280,400 / 640,200.
Step 4 - Compute TMT and AMT owed
Taxable excess = max(AMTI - exemption, 0). TMT = 26% on first 244,500 dollars (122,250 MFS) + 28% above. AMT owed = max(TMT - regular tax, 0).
Step 5 - Identify the AMT crossover
The crossover is the largest bargain element you can add before AMT owed becomes positive. The calculator searches for this value by holding all other inputs fixed and binary-searching the bargain element. Exercises at or below the crossover produce zero AMT cash.
Step 6 - Track AMT vs regular basis
Regular-tax basis per share = strike price. AMT basis per share = FMV at exercise. The 2026 AMT preference is recovered at sale: on a future sale, regular-tax LTCG is larger than AMT LTCG, and the difference creates a year where regular tax exceeds TMT - the year you can apply the Form 8801 minimum tax credit to recover the prior AMT.
Worked Example: David Exercises 5,000 ISOs and Holds
David is a single software engineer at a public tech company. He has 220,000 dollars of regular taxable income (after his standard deduction). His employer granted him 5,000 ISOs at a 10-dollar strike price, vested over four years. The stock now trades at 60 dollars. He exercises all 5,000 in March 2026 and decides to hold past December 31 for the qualifying disposition treatment. He claimed the standard deduction (so SALT add-back is irrelevant for him in this scenario).
Inputs
Filing statusSingle
Disposition planHold past Dec 31
Shares exercised5,000
Strike price$10/share
FMV at exercise$60/share
Bargain element$250,000
Regular taxable income$220,000
DeductionStandard ($16,100)
AMTI Build (Form 6251 Lines 1-4)
Regular taxable income$220,000
+ Standard deduction add-back$16,100
+ ISO bargain element (§56(b)(3))$250,000
= AMTI$486,100
Exemption (2026, Single)
Base exemption$90,100
AMTI under $500,000 phase-out startNo phase-out
Exemption after phase-out$90,100
TMT and AMT Owed
Taxable excess ($486,100 - $90,100)$396,000
26% on first $244,500$63,570
28% on $151,500 above breakpoint$42,420
Tentative minimum tax$105,990
Regular tax on $220,000 single (2026 brackets)approx $42,560
AMT owed (TMT - regular tax)approx $63,430
Form 8801 MTC carryforward generatedapprox $63,430
Cash to plan for: 50,000 dollars to exercise (5,000 × 10) + approx 63,430 dollars of AMT due April 15. Total approx 113,430 dollars before any sale. The AMT is fully a deferral preference (the bargain element is a timing difference), so the entire 63,430 carries forward as a Form 8801 minimum tax credit recoverable in a future regular-tax-dominant year - typically the year David sells the shares.
Counter-scenario - same-year sell: If David instead sells all 5,000 shares same-year at the same 60-dollar FMV, the 250,000-dollar spread becomes ordinary W-2 wages. His total wages become 220,000 + 250,000 = 470,000 (assume itemized recalc unchanged for simplicity). Regular tax on 470,000 single (2026 brackets) is approximately 130,290 dollars. AMT preference = 0. Total tax cost: approximately 130,290 in regular tax with no AMT cash crunch. The hold path costs 42,560 + 63,430 = 105,990 today plus a future LTCG bill, while the sell path costs 130,290 today and is final. The hold path wins by approximately 24,300 dollars in current-year tax, plus the LTCG-vs-ordinary rate spread on any future appreciation above 60 dollars per share.
Quick Facts: ISO Exercise Mechanics
ISO vs. AMT Treatment - 2026
| Element |
Regular Tax |
AMT |
| Grant of ISO |
Not taxable |
Not taxable |
| Vesting of ISO |
Not taxable |
Not taxable |
| Exercise + hold past year-end |
Not taxable |
Bargain element added to AMTI (§56(b)(3)) |
| Exercise + same-year sale (disqualifying) |
Bargain element = ordinary W-2 wages |
No preference (bargain in W-2) |
| Sale meeting §422 holding tests (2yr/1yr) |
Entire gain = LTCG (sale - strike) |
LTCG (sale - FMV at exercise) + Form 8801 MTC recovery |
| Sale failing §422 (after year-end but before 2yr/1yr) |
Spread = ordinary; appreciation = capital gain |
Reverses prior bargain element preference |
| Basis per share |
Strike price |
FMV at exercise (after preference recognized) |
| Form reported on |
Form 1040 line 1 (if disqualifying), Schedule D (if qualifying) |
Form 6251 line 2i, Form 8801 (credit) |
Practitioner Insight
The most common ISO exercise mistake is exercising in late November or December with no exit plan if the stock drops. The AMT preference locks in based on the FMV on the exercise day - if the stock is at 80 dollars on October 15 and you exercise 5,000 shares, you owe AMT on 5,000 × (80 minus strike) regardless of where the price sits on December 31. If the price drops to 30 dollars by year-end, you face the worst-case ISO trap: AMT on phantom income of stock now worth less than the tax bill. The fix is structural: exercise as early in the year as practical (January / February), reserve cash for the AMT, and pre-commit to a year-end decision rule. If the price has dropped meaningfully by mid-November, sell the shares same-year as a disqualifying disposition - the AMT preference disappears, the spread becomes ordinary W-2 wages, and you typically end up with a smaller tax bill than the AMT would have been. The OBBBA 50% phase-out makes this trap more expensive in 2026 because the bump-zone marginal rate (up to 42%) catches a wider band of mid-career exercisers than the prior 25% phase-out did. Always model both paths before exercising.
Real-World Scenario: Maya Stages Her Exercise Across Two Years
Maya is single with 250,000 dollars of W-2 wages. She has 10,000 vested ISOs at a 5-dollar strike with the stock at 55 dollars. A full exercise would create a 500,000-dollar bargain element - well past the OBBBA 500,000-dollar single phase-out start, eliminating most of her exemption and triggering a 100,000+ dollar AMT bill in one year. Her advisor runs the AMT crossover for 2026: with her income mix and standard deduction, she can exercise approximately 4,400 shares (a 220,000-dollar bargain element) in 2026 before TMT exceeds regular tax - the largest exercise that produces zero AMT cash.
2026 plan: Exercise 4,400 shares in February 2026. Bargain element = 4,400 × 50 = 220,000. AMTI = 250,000 (W-2) - 16,100 (std ded) + 16,100 (std ded add-back) + 220,000 = 470,000 (under the 500,000 phase-out start, full exemption preserved). TMT approx = (470,000 - 90,100 - 16,100) × 26% / 28% mix ≈ 95,000. Regular tax on 250,000 - 16,100 = 233,900 single approx 47,450. AMT owed: 0 because she stayed at the crossover. She files Form 6251 to document the basis split and carries no AMT.
2027 plan: Exercise the remaining 5,600 shares in February 2027 against the (likely) higher 2027 exemption. Same logic - target the new-year crossover, exercise up to that level, stay under the AMT cash bill. By year three she has exercised the full 10,000 shares without ever paying AMT cash - and she has a clean AMT basis split that simplifies the Form 8801 credit math when she eventually sells.
The cost of staging: The shares she did not exercise in 2026 may rise (or fall) before she gets to exercise them in 2027. If they rise to 70 dollars, the 2027 bargain element on the remaining 5,600 shares is larger - 5,600 × (70 - 5) = 364,000 - and the 2027 crossover may not absorb the whole exercise. Staging trades AMT cash for share-price risk. Maya makes this trade deliberately because she would rather hold a long-term capital gain position with no AMT cash drag than convert the spread to ordinary income through a disqualifying disposition.
When This Calculator Does Not Cover Your Situation
- Early exercise of unvested ISOs + 83(b) election: Some companies allow early exercise of unvested ISOs. A timely 83(b) election locks in the bargain element at the early-exercise date (usually near zero for early-stage employees). The calculator assumes a normal vested exercise; early-exercise modeling requires separate inputs for grant-date FMV.
- $100,000 ISO limit (§422(d)): Only 100,000 dollars of ISOs (measured by grant-date FMV) can become exercisable in a single calendar year. Excess ISOs are reclassified as NSOs by operation of law. The calculator does not flag this - check your grant docs. Excess shares treated as NSOs face ordinary income at exercise (no AMT preference, but a different tax treatment).
- State AMT (CA, MN, CT, IA): California in particular maintains an aggressive 7% state AMT that can apply on top of the federal hit. Federal AMT relief does not flow through. Model state AMT separately if you live in one of these states.
- Sale of pre-IPO shares: Private-company ISO exercises with no liquid market for the shares introduce additional risks - you owe the AMT in cash but cannot sell shares to fund it. The calculator computes the AMT but does not model liquidity. Do not exercise illiquid ISOs without a confirmed cash source for the AMT bill.
- Cashless exercise: Some employers offer "exercise and sell to cover" structures where the broker sells enough shares to cover the strike + AMT withholding. By definition this is a partial same-year disposition - the sold shares are disqualifying, the held shares are qualifying. The calculator does not model the split-basis result; consult a specialist.
- Form 8801 minimum tax credit recovery: The calculator estimates the AMT owed in the exercise year. It does not project credit recovery in future years. ISO-driven AMT typically recovers in 5 to 10 years (often the year of share sale), but multi-year modeling requires assumptions about future income and sale timing.
- Multiple-year exercise scenarios: The calculator models a single tax year. Staging exercises across multiple years requires running each year separately with the future-year exemption and brackets - which are not yet final until each year's Rev. Proc. is issued.
FAQ: ISO Exercise and AMT
What is the bargain element on an ISO exercise?
The bargain element is the difference between the fair market value of the stock on the day you exercise and the exercise price you pay, multiplied by the number of shares exercised. If you exercise 5,000 shares at a 10 dollar strike when the FMV is 60 dollars, the bargain element is (60 minus 10) times 5,000 = 250,000 dollars. Under IRC section 56(b)(3) the bargain element is treated as an AMT preference item if you hold the shares past December 31 of the exercise year. For regular tax purposes, the exercise itself is not a taxable event - the bargain element is invisible to regular tax until you sell the shares.
How much AMT will I owe if I exercise ISOs and hold past year-end?
AMT owed equals the tentative minimum tax (TMT) minus regular tax (limited to zero). TMT is built by adding the bargain element to your AMTI, subtracting the AMT exemption (90,100 dollars single, 140,200 dollars MFJ for 2026, phased out 50 cents on the dollar above 500,000 / 1,000,000 dollars under OBBBA section 70107), and applying 26 percent on the first 244,500 dollars of taxable excess and 28 percent above. A typical pattern: a single filer with 250,000 dollars of W-2 wages who exercises 5,000 ISOs with a 250,000 dollar bargain element will owe roughly 50,000 to 75,000 dollars of AMT depending on SALT and other adjustments. Use this calculator with your specific inputs to get a real number.
What is the AMT crossover point for an ISO exercise?
The AMT crossover is the largest bargain element you can exercise in a single year before the tentative minimum tax exceeds your regular tax - the point at which AMT cash starts flowing. Below the crossover you can exercise ISOs and not owe any AMT. Above it, every additional dollar of bargain element produces 26 to 42 percent of additional AMT depending on whether you are inside the OBBBA phase-out bump zone. The calculator computes your crossover from your filing status, regular taxable income, SALT, and other AMT adjustments. Spreading large grants across multiple years to keep each year at or below the crossover is the most common AMT-avoidance strategy for ISO holders.
How does a same-year disqualifying disposition eliminate the AMT?
If you sell the ISO shares in the same calendar year you exercise them, the section 56(b)(3) preference disappears. The exercise becomes a disqualifying disposition under IRC section 422 - the bargain element is reported on your W-2 as ordinary wages, your employer withholds federal and FICA, and the spread enters regular tax through wages rather than as an AMT preference. The cost of this approach is converting a potential long-term capital gain (taxed at 0, 15, or 20 percent if held two years from grant and one year from exercise) into ordinary income (up to 37 percent federal). The benefit is no AMT cash crunch on phantom income.
What is my regular-tax basis vs AMT basis after an ISO exercise?
Your regular-tax basis equals the exercise price you paid (the strike). Your AMT basis equals the FMV on the exercise day - higher than the regular-tax basis by the bargain element. The two bases diverge in the year of exercise and stay separate until you sell. When you eventually sell the shares, the regular-tax gain (sale price minus strike) is larger than the AMT gain (sale price minus FMV at exercise), and the difference reverses the prior AMT preference. This is what generates a Form 8801 minimum tax credit usable when regular tax exceeds tentative minimum tax in a future year.
What is Form 3921 and when does my employer issue it?
Form 3921, Exercise of an Incentive Stock Option Under Section 422(b), is issued by your employer for each ISO exercise. It reports: the grant date, exercise date, exercise price per share, FMV per share on the exercise date, and number of shares transferred. You receive Form 3921 by January 31 of the year after the exercise. Use the FMV and exercise price numbers to compute the bargain element on Form 6251 line 2i, and keep the form indefinitely - you need it years later when you sell the shares to compute the AMT-vs-regular basis difference and unlock the Form 8801 credit.
Does AMT apply if I exercise but the stock then drops?
Yes. The AMT preference under section 56(b)(3) locks in based on the FMV on the exercise date. If you exercise on March 1 with the stock at 80 dollars and the price drops to 30 dollars by December 31, the AMT bargain element is still computed on the 80 dollar exercise-day value. You owe AMT on phantom income that no longer exists. This is the worst-case ISO trap and the reason same-year disqualifying disposition is the safe harbor in volatile-stock years - if the price has dropped meaningfully by December, selling the shares at a loss eliminates the AMT preference and at least gives you a deductible capital loss for regular tax.
How does the OBBBA 50% phase-out affect my ISO planning?
OBBBA section 70107 doubled the AMT exemption phase-out rate from 25 percent to 50 percent and reset the phase-out start to 500,000 dollars (single) / 1,000,000 dollars (MFJ) beginning tax year 2026. For ISO exercisers, this matters because the bargain element added to AMTI also clicks through the phase-out. Inside the phase-out band, every additional dollar of bargain element raises AMT by approximately 39 to 42 cents (the 26 / 28 percent AMT rate plus the 13 to 14 percent phase-out tax) - well above the headline 28 percent AMT rate. The most affected exercisers are those whose total AMTI lands between 500,000 and 680,200 (single) or 1,000,000 and 1,280,400 (MFJ) - exactly the range where mid-career equity-comp employees in tech often sit.
Should I exercise early in the year or late in the year?
Exercise timing within a calendar year affects the practical risk of the position more than the AMT computation itself. Exercising early in the year (January or February) gives you 10 to 11 months to evaluate the share price before December 31. If the stock has risen, you keep the ISO treatment by holding past year-end. If the stock has fallen meaningfully, you can sell before year-end as a same-year disqualifying disposition - converting the AMT preference into ordinary wages, often at a much lower tax cost than the AMT would have been. Exercising in November or December removes most of this optionality - by the time you have a clear view of the year-end price, there is little time to react.
Can I use the AMT credit (Form 8801) to recover ISO-related AMT?
Yes. AMT paid on the ISO bargain element is a deferral preference under IRC section 53 and generates a minimum tax credit (MTC) reported on Form 8801. The credit equals the AMT attributable to deferral preferences and carries forward indefinitely. You apply it in future years when your regular tax exceeds your tentative minimum tax. ISO-driven MTC typically recovers within five to ten years - usually in the year you sell the underlying shares, when the AMT-vs-regular basis difference produces a regular-tax LTCG that is larger than the AMT LTCG, generating a year where regular tax substantially exceeds TMT. Track every Form 8801 each year - the credit is easy to forget and easy to leave on the table.
Decision Step: How Should You Exercise Your ISOs?
Route A - Exercise and Hold for Qualifying Disposition
Run the calculator with hold-past-year-end. If the AMT cash is manageable and you have conviction in the stock, the qualifying disposition path (long-term capital gain on sale) usually wins on after-tax terms. Reserve cash for the AMT by April 15 of next year and start a Form 8801 carryforward log. The AMT Calculator stress-tests your full AMT picture; the ISO vs NSO Guide walks through the qualifying-disposition mechanics.
Route B - Same-Year Disqualifying Disposition
Run the calculator with same-year sell. If the AMT cash on the hold path exceeds your reserves, or if the stock has dropped meaningfully since exercise, selling same-year converts the spread to ordinary W-2 wages and eliminates the AMT preference. You give up the long-term capital gain rate on the spread but you avoid the AMT cash crunch on phantom income. This is the standard rescue path for late-year exercises in volatile stocks.
Route C - Stage Across Multiple Years at the AMT Crossover
For larger grants where a one-year exercise would trigger six figures of AMT, stage across two or three calendar years. Exercise up to the AMT crossover each year (the largest bargain element that produces zero AMT cash given your other inputs). The calculator's crossover output gives you the per-year ceiling. The trade-off is share-price risk between years - if the stock rises, the future-year bargain element is larger. The ISO vs NSO Guide includes a worked staging example.
This calculator is for educational and illustrative purposes only. It does not constitute tax, legal, or financial advice. ISO exercise decisions involve significant federal AMT, state tax, securities-law, and liquidity considerations that this tool does not fully model. State AMT (CA, MN, CT, IA) and the Form 8801 minimum tax credit recovery in future years are not modeled here. Consult a qualified tax professional and review your Form 3921 before any ISO exercise. Tax laws are subject to change.