A major difference between NQSOs and RSUs is the way in which they are taxed. Once NQSOs vest, you can exercise and purchase the shares, but you are not required to do so. If you choose to exercise the options, you will generally recognize ordinary income based on the difference between the market value of the stock and the exercise price. When you subsequently sell the shares, any further increase will be taxed as either a short or long-term capital gain.
Example: Your company gives you the right to purchase 1,000 NQSOs at $20 per share. Assuming you exercise the options at vesting and the market value of the stock is $50, you would have to pay $20,000 to exercise the options and would recognize ordinary income of $30,000. Most companies will also allow you to utilize a cashless exercise. With this type of exercise, you can exercise and sell a portion of your shares to cover the option cost and taxes owed resulting in no cash outflow. After you exercise, you can then choose to either sell your remaining shares right away or keep them in your portfolio.
With RSUs, on the other hand, you typically recognize ordinary income based on the market value of the stock on the vesting date. If you choose to sell the shares immediately, there will likely be minimal tax consequences. However, if you hold onto the shares, any subsequent appreciation will then be taxed as either a short or long-term capital gain.
Example: Your company grants you 1,000 RSUs with a four year vesting schedule (25% vesting per year). Assuming the market price is $80 and 250 shares vest one year after the grant date, you would recognize ordinary income of $20,000. Depending on your financial situation, you may then choose to sell the shares immediately or hold onto the shares and sell them in the future.