Founder stock and option planning

The ISO exercise window is often narrower than founders realize — and AMT exposure can arrive before you see a dollar.

Incentive stock options (ISOs) are one of the most tax-advantaged forms of equity compensation available to startup co-founders and early employees. The advantage is conditional: exercise with a small spread, when the company's 409A valuation is still low, and the tax cost can be minimal while the potential gain is still large. Wait until the company is late-stage with a large spread, and you can owe a six-figure AMT bill on gains you haven't yet received in cash.

Who holds ISOs at startups

Founders who receive initial equity as restricted stock at incorporation typically hold common shares, not ISOs. But many co-founders and early executives also receive ISO grants for their operating roles — an initial grant near hire, on a standard 4-year vest with 1-year cliff. Early employees (the first 10–50 people at a seed or Series A company) almost universally receive ISOs.

For these individuals, the ISO exercise decision is one of the most consequential financial choices they will make. The window to exercise cheaply often closes well before the company exits — not because the company fails to perform, but because the 409A valuation rises as the company succeeds.

What happens at exercise: the federal AMT mechanics

When you exercise an ISO, you do not owe federal regular income tax in the year of exercise — even if the stock has appreciated significantly above your strike price.¹ That deferral is the core benefit.

The catch: the spread — the difference between the stock's fair market value (current 409A) and your strike price — is an AMT preference item. It is added to your income for calculating the Alternative Minimum Tax. If the resulting adjusted income exceeds your AMT exemption, you owe AMT in the year of exercise, even though you have received no cash proceeds.

Incremental AMT = tentative minimum tax minus regular income tax already owed. These are ranges for illustration; actual liability requires Form 6251 with your full return inputs.

2026 AMT exemption and OBBBA changes

The One Big Beautiful Bill Act (OBBBA, July 2025) reset the AMT exemption phaseout thresholds back to 2018 TCJA levels and increased the phaseout rate from 25% to 50%.² The result: more taxpayers in the $500K–$800K income range now lose their exemption faster than in recent prior years.

A single filer with $600K of AMTI (e.g., $150K salary + $450K ISO spread) has AMTI $100K above the $500K threshold. At a 50% phaseout rate, the exemption is reduced by $50,000 — from $90,100 to $40,100. Every additional $2 of AMTI costs $1 of exemption until the exemption reaches zero at $680,200. AMT rates are approximately 26% on AMTI below roughly $232,600–$244,500 (indexed) and 28% above.³

The early exercise strategy: minimize AMT before the spread grows

The most effective way to reduce ISO AMT exposure is to exercise before significant appreciation occurs — ideally at or near grant, when the spread is zero or negligible.

How early exercise works

• At grant, the strike price equals the 409A FMV. If you exercise the same week as the grant, the spread is $0. There is no AMT preference item. Your exercise price equals current fair market value.
• Many startup option grants allow early exercise of unvested shares. Companies can permit optionees to exercise unvested options early, receiving restricted shares subject to the company's repurchase right at cost if you leave before vesting. Not all grants allow this — check your option agreement.
• File an 83(b) election within 30 days of early exercise. If you early-exercise unvested ISO shares, filing an 83(b) election locks in the FMV at exercise as your compensation amount (zero if exercised at 409A), starts the capital gain holding period immediately, and starts the QSBS clock. Without the 83(b), each vesting tranche creates a new taxable event — forfeiting most of the planning benefit.

What early exercise accomplishes

Early exercise converts all future appreciation from a potential ordinary income event (spread at exercise) into capital gain accruing from your cost basis forward. If you exercise 100,000 ISOs at $0.25/share (current 409A) today, and the company later exits at $20/share, you have $19.75/share of capital gain — not ordinary income. Had you waited until the 409A reached $8.00/share to exercise, the first $7.75/share would have been an AMT preference item; only gains above $8.00 would be capital gain.

ISO holding period rules: qualifying vs. disqualifying dispositions

To receive long-term capital gain treatment on an ISO sale, you must satisfy both tests for a qualifying disposition:⁴

• More than 1 year from the exercise date
• More than 2 years from the grant date

If you sell before meeting both tests, any gain up to the spread at exercise becomes ordinary income in the year of sale — a disqualifying disposition. This undoes the ISO advantage and is taxed the same as if you had exercised non-qualified options (NQSOs).

Disqualifying dispositions are common at IPOs and acquisitions when employees sell during lockup expiration or execute a same-day exercise-and-sell. If you exercise ISOs and plan to hold, calendar your qualifying disposition dates before any company liquidity event creates sale pressure.

Note: A same-day exercise-and-sale in a company tender offer is a disqualifying disposition. You pay ordinary income tax on the spread, not capital gains. In some cases this is the right call (avoids AMT; you receive cash and pay ordinary income in the same year), but model both options before the tender window opens. See tender offer planning.

California: the ISO double problem

California does not conform to the federal ISO tax treatment. Under California law, the spread on ISO exercise is treated as ordinary income in the year of exercise — not as a deferred AMT item.⁵

Consider a California-resident employee who exercises ISOs with a $400,000 spread:

• Federal: No regular income tax; spread is an AMT preference item. Depending on other income, federal AMT is $50K–$100K.
• California: $400,000 is ordinary income in the year of exercise. At California's 13.3% top rate (income over $1M) or 12.3% (income $677K–$1M), state tax on exercise alone is $49,200–$53,200 — in the year of exercise, with no cash received from a stock sale.

California also has its own AMT at 7%, but the ordinary income treatment typically produces higher California tax than the state AMT alone. For California-based founders and early employees, early exercise when the spread is near zero is even more important — the California ordinary income tax is also near zero when the spread is zero.

QSBS qualification for shares acquired by exercising ISOs

Shares acquired by exercising ISOs can qualify for the Section 1202 QSBS exclusion if the company and shares meet the qualification tests at the time of exercise.⁶ Key tests:

• C-corporation organized in the U.S.
• Gross assets ≤ $75 million at the time of stock issuance
• Active business in a qualifying trade or business (technology, manufacturing, and many others qualify; professional services, finance, and hospitality generally do not)
• Original issuance: acquired directly from the company, not on the secondary market
• Held for more than 5 years for the full 100% exclusion under post-OBBBA tiering

Under the OBBBA (July 2025), the QSBS exclusion tiers at 50% at 3 years, 75% at 4 years, and 100% at 5 years, with a $15M per-issuer cap per taxpayer.⁷ Early exercise is critical: the QSBS 5-year holding period clock starts from the date of exercise (assuming an 83(b) election is filed for unvested shares), not from the vesting date.

California still does not conform to QSBS. California residents owe California income tax (up to 13.3%) on the full federally excluded gain, regardless of the federal exclusion. See the QSBS planning guide for detail on California non-conformity and mitigation strategies.

The AMT credit: prepaid tax, not permanently lost tax

If you pay AMT in the year of ISO exercise, you generate a minimum tax credit (Form 8801) equal to the incremental AMT paid.⁸ This credit carries forward indefinitely and reduces your federal regular income tax in future years when your regular tax liability exceeds your tentative minimum tax.

For most founders who hold shares to a qualifying exit, the regular capital gains tax owed on the sale will exceed AMT in the exit year, allowing some or all of the credit to be recovered. The AMT paid on exercise is often effectively a prepayment of future tax rather than a permanent additional cost.

The exception: if the company fails or shares are sold for less than the AMT cost basis, the credit may exceed available regular tax for years or be only partially recoverable. Paying AMT on a company that never exits is the true downside of late-stage ISO exercise without a simultaneous sale.

Decision framework: when to exercise ISO grants

The numbers: early vs. late exercise on the same grant

Consider 500,000 ISOs granted at $0.50/share at seed stage (current 409A = $0.50). At Series C, the 409A has risen to $6.00/share. The company exits at $18/share.

Early exercise scenario (exercise at grant, $0 spread):

• Exercise cost: $250,000 ($0.50 × 500K shares)
• AMT preference item: $0
• Federal AMT: $0
• California ordinary income at exercise: $0
• At exit ($18/share): $9M gross proceeds. Cost basis = $250K. Long-term capital gain = $8.75M. Potentially QSBS-excluded if 5-year hold.

Late exercise scenario (exercise at Series C, $5.50/share spread):

• Exercise cost: $250,000 (same strike price)
• AMT preference item: $2,750,000 ($5.50 × 500K shares)
• Federal AMT: potentially $600K–$750K, before AMT credit
• California ordinary income at exercise: $2,750,000 × up to 13.3% = up to $365,750 — due in the year of exercise, before any sale
• At exit ($18/share): $9M gross proceeds. Cost basis = $3M (409A at exercise). Long-term capital gain = $6M. AMT credit partially recoverable in exit year.

The difference between the two paths is not just the dollar amount of taxes — it is when the tax arrives and whether you have cash to pay it. Early exercise moves virtually all tax to the exit year; late exercise forces a large tax payment during a period when the stock is still illiquid.