RSU vs ISO vs NSO: What's the Difference and How Is Each Taxed?

If you work in tech, your offer letter probably included equity. The three most common types are restricted stock units (RSUs), incentive stock options (ISOs), and non-qualified stock options (NSOs). The RSU vs ISO vs NSO question matters because the three look similar on a grant summary but are taxed very differently, and mixing them up is one of the most common planning mistakes we see among Bay Area tech employees.

This guide is educational, not tax or legal advice. Your plan documents and a qualified tax professional control your actual situation.

The short version

• RSUs: you receive shares when they vest, you pay nothing for them, and their value is taxed as ordinary income at vesting, with withholding.

• NSOs: you pay an exercise price to buy shares. The spread at exercise is taxed as ordinary income, with withholding. Later changes are capital gains or losses.

• ISOs: you pay an exercise price to buy shares. There is usually no regular income tax at exercise, but the spread can trigger the Alternative Minimum Tax. Selling early can turn part of the gain into ordinary income.

RSUs: simple, but taxed at vesting

An RSU is a promise to deliver shares once a vesting condition is met. When the shares vest, their market value counts as ordinary wage income, whether or not you sell. Your employer usually withholds some tax by selling or withholding shares, but the flat supplemental withholding rate often does not match your real bracket, which can leave a gap at tax time. We cover this in more detail in RSU Taxes Explained.

After vesting, your cost basis is the value at vesting. Further gains or losses are capital gains or losses.

NSOs: tax at exercise

A non-qualified stock option lets you buy shares at a set exercise price. When you exercise, the difference between the market price and your exercise price (the spread) is taxed as ordinary income, and it is usually reported on your W-2 and subject to withholding. Your basis then becomes the market value on the exercise date, and later changes in price are capital gains or losses.

The key planning question with NSOs is timing: exercising when the spread is small, or in a lower-income year, can reduce the tax cost. Exercising a large grant all at once can push you into a higher bracket.

ISOs: favorable treatment, with traps

Incentive stock options can receive special tax treatment. If you meet the holding requirements, which are generally holding the shares at least two years from grant and one year from exercise, the gain can be taxed as long-term capital gain instead of ordinary income.

The catch is the Alternative Minimum Tax. Exercising ISOs and holding the shares does not create regular taxable income, but the spread can count as an AMT adjustment, which may create a large tax bill on paper gains if the stock later falls. If you sell before meeting the holding periods (a disqualifying disposition), part of the gain is taxed as ordinary income instead.

Whether and when to exercise ISOs is a strategy decision, not a default. See Should You Exercise Your ISOs Early? for the deeper discussion. If your company lets you exercise before vesting, read The 83(b) Election Explained too.

California adds another layer

California taxes capital gains at ordinary income rates and does not offer the federal long-term capital gains rate break. California also has its own AMT rules, so an ISO exercise can look different on your state return than on your federal one.

Concentration risk applies to all three

Whichever type you hold, equity compensation tends to concentrate wealth in your employer, the same company that pays your salary. If the stock falls, your income and your net worth can fall together. Many people plan around a target maximum for any single stock and a schedule for diversifying.

Frequently asked questions

What is the main difference between RSUs and stock options? RSUs deliver shares to you when they vest, and the value at vesting is taxed as ordinary income. Stock options (ISOs and NSOs) give you the right to buy shares at a fixed price, and the tax event happens when you exercise or sell.

Are ISOs better than NSOs? ISOs can offer more favorable tax treatment if you meet the holding periods, but they carry Alternative Minimum Tax risk and extra rules. Neither is automatically better. It depends on your situation.

Which is taxed first, an RSU or an option? RSUs are taxed at vesting. NSOs are taxed at exercise. ISOs generally have no regular tax at exercise, but may create AMT, and are taxed when sold.

Do I owe tax if I don't sell my shares? For RSUs and NSOs, yes. The vesting or exercise event is taxable even if you hold the shares. For ISOs, AMT may apply even without a sale.

Questions to ask before you act

• Which of my grants are RSUs, ISOs, or NSOs, and what are the exact vest and expiration dates?

• How much tax will be withheld, and how much will I owe in total?

• Could exercising or selling push me into a higher bracket or trigger AMT?

• How much of my net worth is in one company's stock?

• What happens to unvested or unexercised equity if I leave?

Where we can help

A clear plan means knowing which grants you have, when each one creates a tax event, and how those events fit with the rest of your income. If you want to walk through your equity picture, schedule a free consultation.

This article is for educational purposes only and does not constitute investment, tax, or legal advice.