Early Exercise Stock Options Tax Calculator
Early-exercising stock options (when company allows) combined with an 83(b) election locks in today's low FMV as the tax basis, converting all future appreciation to long-term capital gains. The most powerful equity tax strategy in early-stage startups.
| Early exercise + 83(b) | |
| Cost to exercise (strike × shares) | — |
| Tax owed at 83(b) (if NSO) | — |
| Tax at exit (LTCG on full appreciation) | — |
| Total tax | — |
| Standard exercise at vest | |
| Ordinary tax on spread at vest | — |
| LTCG on post-vest appreciation | — |
| Total tax | — |
Early exercising stock options — when the company allows you to exercise before vesting — combined with an 83(b) election locks in today's low FMV as the tax basis. All future appreciation converts from ordinary income (taxed at 32-37%) to long-term capital gains (15-20%). For founders and very early employees in startups with low strike prices, this can save millions in tax.
How Early Exercise Works
If your company allows early exercise (some do, some don't — check option agreement), you can exercise unvested options. You pay the strike price today and file an 83(b) election within 30 days of exercise. The 83(b) recognizes ordinary income equal to (FMV − strike) × shares NOW, not at vest. If FMV ≈ strike (early stage), this is nearly free.
The Tax Math
Without early exercise: pay ordinary tax (NSO) or AMT (ISO) on the FULL spread at each vesting date. With early exercise + 83(b): pay tax on (FMV today − strike) which is often near zero. Future appreciation (exit FMV − FMV today) is LTCG. For a founder with 4M shares at $0.001 strike and $50 exit, early exercise saves typically $1-3M of tax.
Risks
(1) Leave before vest: company repurchases unvested shares at strike. You've lost the cash you paid. (2) Company fails: strike investment is wiped out. (3) FMV drops: 83(b) is irrevocable — you can't un-elect. (4) Cash required: strike × shares can be $50K-$500K for early employees. Only do early exercise if you can afford to lose the strike investment.
Last updated May 2026. Sources: Cornell IRC §83, IRS Form 6251 (AMT).