ISO vs NSO Stock Option Tax 2027 Comparison Calculator
Compare the 2027 federal tax impact of exercising and selling Incentive Stock Options (ISOs) vs Non-Qualified Stock Options (NSOs).
ISO vs NSO Tax Mechanics
Non-Qualified Stock Options (NSOs): bargain element (FMV minus strike) is taxed as ORDINARY INCOME at exercise — full marginal rate (up to 37%) plus FICA (7.65% to wage base) plus state. Incentive Stock Options (ISOs): NO regular tax at exercise IF you meet the qualifying disposition holding period (>2 years from grant AND >1 year from exercise). Bargain element IS an AMT preference item. Source: IRC §421-424, §83. Last updated: May 2026.
ISO Qualifying Disposition: The Holy Grail
If you hold ISO shares more than 2 years from grant date AND more than 1 year from exercise date, the entire spread between strike and sale price is long-term capital gain (20% + 3.8% NIIT = 23.8% top). NSO equivalent: $8 bargain element taxed at 37% ordinary, then any further appreciation at 23.8%. The difference on a $300K gain can be $50K-$80K in saved federal tax.
ISO AMT Trap
The bargain element IS an AMT preference at exercise (even though no regular tax). For high earners, this can trigger Alternative Minimum Tax — a tax pre-payment on phantom income. The AMT generates a Minimum Tax Credit (Form 8801) recoverable in future years. Plan ISO exercises carefully; many tech employees got crushed by this in the dot-com era.
Strategy: Early Exercise + 83(b) + ISO
Combine three techniques: early exercise ISOs while FMV is low (often grant date with vesting), file 83(b) within 30 days to lock in the low FMV, and hold for qualifying disposition. Result: ZERO bargain element ever, ZERO AMT ever, ZERO ordinary income, and ENTIRE sale price is long-term capital gain. The single most tax-efficient way to monetize startup equity.
Frequently Asked Questions
What's the main tax difference between ISO and NSO?
NSO: bargain element taxed as ordinary income at exercise (37% federal + FICA + state). ISO with qualifying disposition: NO regular tax at exercise, only LTCG (20% + 3.8% NIIT) on entire spread at sale. ISO can also trigger AMT \u2014 but creates a recoverable Minimum Tax Credit.
What's the ISO qualifying disposition holding period?
More than 2 years from grant date AND more than 1 year from exercise date \u2014 BOTH conditions must be met. If you sell earlier (disqualifying disposition), the spread becomes ordinary income just like an NSO \u2014 losing the tax advantage. Track both dates carefully.
Does ISO exercise trigger AMT in 2027?
Yes \u2014 the bargain element at exercise is an Alternative Minimum Tax preference item. For high earners with large ISO exercises, this can trigger substantial AMT. The good news: AMT from ISO timing creates a Minimum Tax Credit (Form 8801) that's recoverable in future years when regular tax exceeds tentative AMT.
What's the $100K ISO annual limit?
Per IRC \u00a7422(d), only $100,000 worth of ISOs (measured at grant-date FMV) can become exercisable in any single calendar year. Excess is treated as NSO. If your grant vests $200K in a single year, only $100K gets ISO treatment \u2014 the rest is NSO. Companies stagger vesting to maximize the limit.
Should I early-exercise my ISOs?
If you (a) can afford the strike price + AMT, (b) believe in the company's success, (c) can hold 5+ years to a 2x+ exit, then YES \u2014 early exercise + 83(b) is the most tax-efficient strategy. You convert all future appreciation to long-term capital gain at 20% + 3.8% instead of ordinary income at 37% + NIIT. Risk: lose strike if company fails.
What happens with ISO if I leave the company?
You typically have 90 days post-employment to exercise vested ISOs \u2014 any later loses ISO status (treated as NSO). Some plans extend this to 7-10 years post-employment but the IRS still requires the 90-day window for ISO treatment. Many startup employees leave significant ISO value on the table by not exercising in time.