ISO
ISO is a type of employer-issued stock option under Section 422 of the tax code that, if held for the required periods, qualifies for favorable long-term-capital-gains tax treatment on the entire gain — making it more tax-advantaged than NQSOs (Non-Qualified Stock Options).
To receive ISO tax treatment, the option holder must (1) hold the shares for at least 2 years from the grant date and (2) hold the shares for at least 1 year from the exercise date. If both conditions are met (a 'qualifying disposition'), the entire gain on the eventual sale is taxed at long-term capital gains rates. If either condition fails (a 'disqualifying disposition'), the bargain element is taxed as ordinary income.
The complication with ISOs is the AMT exposure at exercise. The bargain element (current market price minus strike price) is a preference item for AMT purposes — meaning a taxpayer can owe AMT in the year of exercise even though no regular-tax-recognized income occurred. This 'paper-gain' AMT has been a significant planning problem for tech employees in past years, sometimes producing tax bills well in excess of actual cash received from the option.
The AMT paid on ISO exercise creates an AMT credit that can offset regular tax in future years. When the shares are eventually sold, the regular-tax basis increases by the bargain element, and the AMT credit can offset some or all of the resulting regular tax. Planning around ISO exercise typically involves modeling both regular tax and AMT in the exercise year and the sale year to optimize the timing.
Synthetic ISO grants need: grant date, expiration date, vesting schedule, strike price, FMV at grant, current FMV, exercised-to-date, AMT preference accumulated, AMT credit balance carryforward. Test scenarios should include the full lifecycle: pre-cliff, partial-vesting, mid-exercise (pre-IPO or post-IPO), post-disqualifying-disposition, post-AMT-credit-recovery. The §422(d) $100k aggregate vesting limit creates ordering questions when grants exceed the limit.
Common pitfalls
- Forgetting the §422(d) $100k vesting limit — only $100k of FMV (at grant) of ISO stock can vest in any year; excess vests as NSOs.
- Treating exercise as a non-event because there's no regular-tax recognition — the AMT preference can produce a real tax bill.
- Disqualifying dispositions can recharacterize gain as ordinary income — a sale at month 11 of post-exercise holding period loses LT treatment.
- Letting the option expire (10-year max) without exercise — once expired, no further opportunity; many post-IPO scenarios involve race against expiration.
Examples
Grant 50,000 ISOs at $4 strike (FMV at grant $4 — qualifying). Exercise all at FMV $50: bargain element = 50,000 × ($50 − $4) = $2.3M. AMT preference: $2.3M. AMT due (rough): $600,000. Regular-tax basis: $200,000 (50,000 × $4). AMT basis: $2.5M. If shares hold and rise to $80: sale produces LT gain $30/share × 50,000 = $1.5M (regular). AMT credit recovers in years following sale.