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Analysing the fundamental disparities between Non Qualified Stock Options and Incentive Stock Options is essential to understand stock options.

Companies offer stock options as a form of equity compensation to their employees. Rather than directly giving shares of stock, companies provide employees with derivative options on the same. The specific terms and conditions related to these stock options are clearly articulated for the employees in an ‘options agreement’ agreement. 

Two stock options exist: ISO options or statutory stock options and NSO, also known as non-statutory stock options. An employee primarily benefits from a stock option when it outperforms the exercise price. This implies when the value of a company’s shares rises higher than what one would have paid for them initially.

Let’s explore ISO vs NSO and compare the main differences.

What are stock options?

At a fixed price in the future, a certain number of company shares can be purchased by the recipient who holds stock options. These are a form of employee equity.

The fixed price remains unchanged as the stock value escalates over time. Following a period (vesting), you possess the opportunity to purchase (exercise) the stock at a nominal cost and vend it later for an augmented, higher price. In simpler terms, options provide an avenue for low purchase and high sale.

How do stock options work?

Establishing vesting rules is the mechanism through which stock options operate: recipients must meet these conditions before attaining full ownership of their awarded options. Once the vesting period concludes, recipients can then exercise–or put into action–these previously restricted shares.

  1. Vesting

Whether ISO vs NSO, stock options usually undergo stock vesting – a waiting period characterised by both time-based criteria and milestones. During this interim phase, recipients do not possess complete control over their stock options. However, once the prescribed duration lapses, they gain full authority. Recipients can then make a decision to purchase company shares or sell them for profit.

Most companies find vesting sensible; they prefer not to hire individuals and offer them options only for these employees to quit merely two months later. 

  1. Exercising stock options

After vesting, the actual ownership of the options is transferred to you. You may then exercise these options by purchasing the shares at an initially agreed price – typically set as the fair market value (FMV) upon your grant. Upon exercising them, you also have a choice to sell these shares.

What are non-qualified stock options?

So, what is NSO? On the contrary, Non-Qualified Stock Options differ in their regulatory framework from ISOs. They are a type of stock option that does not adhere to identical rules. Typically extended to an expansive employee spectrum, companies offer NSOs to rank-and-file personnel, contractors and consultants. Between ISO vs NSO, NSOs do not undergo identical tax treatment. This disparity introduces more intricate tax implications.

What are incentive stock options?

Now, what is ISO? Employees receive incentive stock options, a specific type of stock option, as part of their compensation package. Key employees like executives and managers usually receive ISOs. This design aims to offer them incentives towards the company’s long-term success. The Internal Revenue Code governs the tax treatment of ISOs, subjecting them to specific rules and regulations.

Tax implications of ISO vs NSO


ISO stock options, akin to NSOs, bear the imposition of long-term capital gains when their holders exercise them and retain ownership for a minimum period of one year; furthermore, these assets must be held continuously from the grant date for at least two years.

If an option holder opts to sell their shares within a year of executing them – for instance, to finance the exercise cost – such a sale will not qualify for ISO tax treatment. Instead, it falls under the ‘disqualifying disposition’ category and incurs wage income tax on the discrepancy between Fair Market Value (FMV) at time-of-sale versus strike price. In this case, they would face similar taxation to NSOs; moreover, any difference between share FMV when sold against its initial purchase or strike value is subjectable under standard wage income taxes.


The exercise and sale of NSO attract taxation. When an individual exercises the option, we impose taxes on the ‘Spread’; this refers to the disparity between FMV (Fair Market Value) at grant time and strike price at exercise time – for employees, it takes the form of wage tax; for non-employees, these are considered self-employment wages subject to taxation.

Regular income tax and employment taxes apply to both types of wages. Should the option holder sell the stock within one year from exercising it, they must pay taxes on their ‘Gain’ – this is calculated by subtracting Final Market Value (FMV) at exercise time from the final sale price and applying short-term capital gains tax rate to that amount. 

However, suppose an individual holds onto these stocks for more than a year before selling them after exercising them. In that case, the long-term capital gains tax rate governs taxation for any accrued profit or gain on such transactions.

How ISOs and NSOs work?

ISOs typically follow a vesting schedule initiated from the grant date, when the options were issued, allowing employees to exercise options only after vesting. Upon exercising ISOs, employees must calculate their Alternative Minimum Tax (AMT) liability by including the spread if they hold the acquired shares at the year-end. Holding the shares for at least one year post-exercise and two years post-grant qualifies them for long-term capital gains tax treatment instead of ordinary income taxes.

Exercising NSOs is comparatively simpler. Upon exercise, employees are required to pay ordinary income taxes on gains, determined by the difference between the strike price and the fair market value at the time of exercise. 

Subsequently, they are subject to capital gains tax rates on any further gains from the stock between the purchase and sale prices. The duration of the holding period after exercise determines whether short-term capital gains tax rates (for holding periods under a year) or long-term capital gains tax rates (for holding periods exceeding one year) are applicable.

NSO vs ISO- A detailed insight into their difference

FeatureIncentive Stock Options (ISOs)Non-Qualified Stock Options (NSOs)
EligibilityLimited to employeesAvailable to employees, consultants, directors, etc.
Tax Treatment at ExerciseGenerally not subject to ordinary income taxSubject to ordinary income tax upon exercise
Alternative Minimum Tax (AMT)May trigger AMT if exercised and held beyond the vesting periodNot subject to AMT upon exercise
Exercise PriceMust be at least equal to the fair market value of the stock at the grant dateNo such restriction, can be set below the fair market value
Holding PeriodMust hold the stock for at least one year after exercising to qualify for long-term capital gains tax treatmentNo specific holding period requirement
Taxation upon SaleEligible for favourable long-term capital gains tax rates if sold after holding for the required periodTaxed at ordinary income tax rates upon sale
Employer WithholdingNo withholding requirement upon exerciseEmployers must withhold taxes upon exercise


ISO vs NSO  fulfill distinct roles. ISOs are favoured as employee stock options in startup settings due to their tax advantages, often forming part of an option pool dedicated to retaining vital talent in early-stage companies.

Both types have their merits. ISO options provide advantageous tax treatment for employees but carry stricter limitations. NSOs, on the other hand, serve as valuable equity compensation, suitable for rewarding non-employees like contractors and service providers.


Do advisors receive ISOs or NSOs?

Only employees are eligible for ISOs, while NSOs can be granted to various service providers, including directors, contractors, advisors, and employees.

Are NSOs liable for AMT?

Exercising an ISO may trigger an Alternative Minimum Tax (AMT) applicable to affluent taxpayers or in a significant spread scenario. NSOs, on the other hand, are subject to higher ordinary income tax rates on the spread, along with payroll taxes such as Medicare and FICA.

Are NSOs subject to double taxation?

If your employer grants you nonqualified stock options (NSOs), it constitutes a form of equity compensation akin to incentive stock options (ISOs). However, unlike ISOs, NSOs may result in double taxation.

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