business · 2026-05-01

Stock option exercise tax + cost calculator

Project the cost + tax to exercise NSO or ISO stock options at IPO or before — strike price + bargain element + ordinary or AMT tax.

Total cash required (exercise + tax)
$342,000

Inputs

Strike price per share$3
Current FMV per share$18
Shares to exercise50,000
Option typeISO (Incentive Stock Option)
Federal ordinary rate %32%
Federal LTCG rate %20%
AMT rate %28%

Supporting metrics

Exercise cost (strike × shares)$125,000
Immediate tax owed$217,000
Bargain element$775,000

About this calculator

Exercising options — the hidden cash cost

The exercise cost (strike × shares) is the obvious number. The tax cost — especially for ISOs triggering AMT — is often as large or larger and surprises early-stage employees who don't have liquidity.

NSO vs ISO at exercise

The math

Default scenario: 50,000 shares × $2.50 strike, current FMV $18:

For most early employees, this is a deal-breaker without one of:

The strategic choices

FAQ

What's the 83(b) election?

Tells the IRS to tax restricted stock at GRANT date FMV (often $0 or near-zero for founders) instead of vesting date FMV (often much higher). Must be filed within 30 days of grant — no exceptions, no extensions. Game-changer for founders/early employees; meaningless once the company has appreciated.

How does AMT recovery work?

AMT paid creates a Min Tax Credit (Form 8801) usable in future years against regular tax to the extent regular tax exceeds tentative AMT. Most ISO-exercise AMT recovers fully within 5-15 years if you sell over time at LTCG. Track carefully — this is a real refundable asset.

Should I do same-day-sale on ISOs?

Defeats the purpose of ISO. A same-day sale (exercise + sell within the same year, or before holding 1 year post-exercise) is a 'disqualifying disposition' — bargain element taxed at ORDINARY rates instead of LTCG. Use NSOs for same-day-sale liquidity events; preserve ISOs for long-hold LTCG strategy.