Incentive Stock Options (ISOs) offer potential tax advantages to U.S. employees but are governed by strict IRS rules, including a 90-day exercise window after termination and significant AMT risk. Non-qualified Stock Options (NSOs) are simpler and more flexible, can be granted to anyone (advisors, contractors, international staff), and provide the company with a valuable tax deduction. Many employee-friendly startups are now strategically opting for NSOs to offer extended exercise windows.
Key takeaways
- Grant ISOs to U.S. employees for the potential tax benefits, but only if you accept the 90-day exercise window.
- Use NSOs for all non-employees (advisors, contractors) and international hires.
- Always get a third-party 409A valuation to set a legally defensible strike price before issuing any equity.
- The ISO Alternative Minimum Tax (AMT) can force employees to pay a huge tax bill on paper gains, even without selling stock.
- Consider NSOs for all employees to offer extended exercise windows, a powerful recruiting and retention tool.
- Don't forget the NSO superpower: your company gets a cash-free tax deduction when employees exercise.
You can’t compete with Google on salary. Your most powerful weapon in the war for talent is equity. But the moment you decide to grant it, you face a foundational choice: ISOs or NSOs?
This isn’t just a legal formality. The choice between Incentive Stock Options (ISOs) and Non-qualified Stock Options (NSOs) has real consequences for your ability to hire, who you can compensate, your company’s finances, and your relationship with your team. Getting it wrong creates tax nightmares and sours relationships with departing employees.
Let's cut through the noise and get to the actionable framework a founder needs.
The Core Tradeoff: Employee Tax Dreams vs. Company Flexibility
At the highest level, the decision boils down to a single question: Are you optimizing for a potential (but complicated) tax break for your US employees, or for maximum flexibility for the company and your entire team?
Incentive Stock Options (ISOs) are the "classic" startup option. They offer a potential tax advantage to US employees, but they come with a thicket of rigid IRS rules you cannot bend.
Non-qualified Stock Options (NSOs) are simpler and more flexible. They can be granted to anyone—advisors, contractors, international hires—and they give your company a valuable tax deduction.
ISOs are the default for most US-based, early-stage employee grants. The entire premise is built around favorable tax treatment for the employee.
With an ISO, an employee can potentially pay much lower taxes. If they hold their shares for at least two years from the grant date AND one year from the exercise date, their entire gain—from the strike price to the final sale price—is taxed as a long-term capital gain (~15-20%). This is a huge advantage compared to ordinary income tax rates, which can be 37% or higher.
Example: An engineer exercises options with a $10,000 strike price and sells the stock years later for $510,000. With ISOs (held properly), their $500,000 gain is taxed at the capital gains rate, saving them…
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Frequently asked questions
- How much does a 409A valuation cost?
- For an early-stage startup, a 409A valuation from a reputable firm typically costs between $2,000 and $5,000. This is a non-negotiable cost of granting equity.
- What happens if an ISO grant exceeds the $100k limit?
- The portion of the grant that becomes exercisable for the first time in a calendar year worth over $100,000 (valued at the strike price) is automatically and unavoidably treated as an NSO for tax purposes.
- Can you switch an ISO to an NSO?
- Yes. Any modification to an ISO that violates the IRS rules, such as extending the post-termination exercise window beyond 90 days, automatically converts it into an NSO.
- Do candidates prefer ISOs or NSOs?
- Candidates often default to asking for ISOs, hearing they are "better." However, experienced candidates increasingly understand the downside of the 90-day exercise window and AMT risk, and many now prefer the flexibility of an NSO with a longer exercise period.
- Can we let employees exercise options before they vest?
- Yes, this is called "early exercising." It can be a powerful strategy to minimize future taxes but comes with its own set of rules and tax implications (like an 83(b) election) that your startup lawyer must help you navigate.
