ISO vs. NSO – Employee Stock Options Basics


ISO and NSO, what do these terms mean? These terms stand for incentive stock options (ISOs) and non-qualified stock options (NSOs or NQSOs) respectively. They are mostly common among companies which use their company stocks as part of the employee’s compensation and/or retirement benefit packages.

NSO or NQSO are options to buy shares of company stock at a stated price and can be exercised over a specific period, i.e. over 10 years. The exercise price is normally 100% of fair market value on the date the option is granted, but it can be set lower.

ISO is an option to buy shares of company stock at a set price on the date of grant and can be exercised over a period of up to 10 years. Like NSO, the exercise price of ISO is normally set at the fair market value on the date the option is granted.

After reading the above definitions of ISO and NSO you are probably wondering: what are the differences of these two options? The differences mostly lie in the employer tax deductions and income tax treatment of exercising ISO and NSO options to the employees.

With most NSOs, if the employee opts to exercise the options to hold the shares of company stock, then the employee must recognize as ordinary income the amount of difference between the option grant (exercise) price and the fair market value of the underlying stock at the time of exercise. This income is subject to social security (FICA) and federal unemployment (FUTA) taxes. Subsequently, the employee will recognize either capital gains or losses on any appreciation or depreciation in the stock value from the day of exercise until the day the employee sells the stock. Alternatively, the employee can opt to exercise to sell, and then the employee will pay income and social security taxes on the amount realized on the sale of the stock minus the option price.

Unlike NSO, where the employee has to pay ordinary income taxes when he or she exercises the options to hold the stock, an employee who receives ISOs does not have to pay regular income tax at the time of exercise. If, after the exercise the shares are held for at least one year from the date of exercise and two years from the date of grant of the options (1year/2year holding period requirements), the sale of the shares will result in long-term capital gain from the date of the option grant to the date of sale of the stock. If, the 1year/2year holding periods are not met, then the sale becomes a disqualifying disposition and the ISO is treated like a NSO, where the difference between the option price and the fair market value at the time of exercise will be taxed as ordinary income.  

The difference between the taxation of a disqualifying disposition of an ISO and that of an NSO is that the recognized ordinary income from the disqualifying ISO is not subject to social security and federal unemployment taxes.

Here are two examples explaining how ISO and NSO work:

  • Adam received 100 shares of NSOs from his employer ABC Industry, Inc. on February 8, 2017. The option exercise price is $5 per share. On the date of grant, there is no taxation to Adam. On March 15, 2018, when the fair market value of the ABC’s stock is $10 per share, Adam exercised his options. Adam would recognize $500 ($10-$5=$5 times 100 shares) as ordinary income. On March 20, 2019 when the ABC’s stock price rises to $20, Adam sells all of his 100 shares of ABC stock. Adam would recognize $1,000 as long-term capital gain and would pay capital gain taxes because he has held the stocks for more than 12 months after he exercise his NSOs. If, instead of exercising the NSOs on March 15, 2018, Adam waited until March 20, 2019 to exercise the option and simultaneously sell the underlying stock, then, Adam would recognize all proceeds from the sale, $20 stock price/share – $5 option price times 100 shares = $1,500, as ordinary income and would pay regular income tax and social security taxes on this $1,500.

  • Eve received 100 ISOs from XYZ Industry Inc. on January 28, 2017. The option exercise price is $5 per share. If Eve exercised her ISOs on January 31, 2018 when the fair market value of the stock was $10 per share, she would recognize no income for regular tax purposes. If subsequently, Eve sells the stocks when its price rises to $20 on February 9, 2019, she would be able to recognize the entire gain of $ 1,500 as long-term capital gain because she has met the 1year(from exercise)/2 year(from grant) holding period requirements. If,  Eve sells the stocks on December 31, 2018, then she has not met the 1year/2year holding period requirements. In this case, the $500 from the exercise of the options on January 31, 2018 would be treated as ordinary income and the subsequent gain of $1,000 from sale of the stocks on December 31, 2018 would be recognized as short-term capital gains.

With NSO, the employer can take a deduction in the amount of income that is taxed to the employee. With ISO, however, if the employee complies with the 1year/2year holding period requirements, the employer gets no tax deduction from it.

If an employee is given stock options, he or she needs to be clear what kind of options they are. There is an employment requirement for employees who receive ISOs. That is, the employee who receives ISOs must remain employed with the same employer from the time of the grant of the options until at least 3 months before the exercise.

Another difference between these two employee stock options is that ISOs are not transferable except at death, while NSOs are transferable during the employee’s lifetime.