Equity Compensation Tax: RSU, ISO, and ESPP

Equity compensation can be one of the fastest ways to build wealth, but without the right tax strategy it can also produce costly surprises. This guide breaks down the four most common forms of equity, RSUs, ISOs, NSOs, and ESPPs, with real examples so you know exactly what is taxed, when, and how to plan ahead.

What are the four main types of equity compensation?

The four most common forms are RSUs, NSOs, ISOs, and ESPPs, and each is taxed at a different point and rate. The snapshot below summarizes when tax is due, the rate that applies, and the biggest risk for each.

How are RSUs (restricted stock units) taxed?

RSUs are taxed as ordinary income at vesting, based on the fair market value of the shares that day, and that value is subject to payroll tax and reported in Box 1 of your W-2. When you later sell, any change in price after vesting is taxed as a capital gain or loss.

When you pay tax:

• At vesting: The market value of your shares is treated as ordinary income and subject to payroll taxes.
• At sale: If the price changes after vesting, the difference is taxed as capital gains.

Example:

You have 2,000 RSUs that vest on January 1 when the stock price is $25. $25 x 2,000 = $50,000 of ordinary income.

Your employer withholds about 22% for federal tax ($11,000), but if your actual tax rate is 35%, you may owe another $6,500 at tax time.

You keep the shares and sell more than a year later at $30. $30 - $25 = $5 gain per share x 2,000 = $10,000 long-term capital gains.

How are NSOs (non-qualified stock options) taxed?

NSOs are taxed as ordinary income at exercise on the spread between the fair market value and your strike price, with payroll tax applied, and the amount appears on your W-2. Any appreciation after exercise is then taxed as a capital gain when you sell.

When you pay tax:

• At exercise: You pay ordinary income tax and payroll taxes on the difference between the stock price at exercise and your strike price.
• At sale: Any increase in value after exercise is taxed as capital gains.

Example:

You have 5,000 NSOs with a strike price of $5. You exercise when the stock is trading at $15. $15 - $5 = $10 spread per share x 5,000 = $50,000 ordinary income.

This amount appears on your W-2.

Six months later, you sell at $18. $18 - $15 = $3 gain per share x 5,000 = $15,000 short-term capital gains.

How are ISOs (incentive stock options) taxed, and when does AMT apply?

ISOs create no regular income tax at exercise, but the spread between fair market value and the strike price is an Alternative Minimum Tax (AMT) preference item that can generate a tax bill with no cash from a sale. If you hold the shares at least one year after exercise and two years after grant, the entire gain is taxed at long-term capital gains rates.

When you pay tax:

• At exercise: No regular income tax, but the difference between the market value and strike price is counted for Alternative Minimum Tax (AMT) purposes.
• At sale: If you hold shares for at least 1 year after exercise and 2 years after grant, the gain is taxed entirely as long-term capital gains.

Example:

You have 10,000 ISOs with a strike price of $3. You exercise when the stock price is $10. $10 - $3 = $7 spread per share x 10,000 = $70,000 counted for AMT.

You haven't sold, so you have no regular income tax yet, but you might owe AMT.

You sell more than 1 year after exercise and 2 years after grant at $14. $14 - $3 = $11 gain per share x 10,000 = $110,000 long-term capital gains.

If you had sold right after exercising, part of the $7 spread would have been taxed as ordinary income.

How is ESPP (employee stock purchase plan) income taxed?

An ESPP triggers no tax at purchase, even when you buy at a discount. At sale, the discount is generally taxed as ordinary income and the remaining gain as capital gain, with more favorable treatment if you hold the shares more than two years from the offering date and one year from purchase (a qualifying disposition).

When you pay tax:

• At purchase: No tax is due, even if you buy at a discount.
• At sale: A portion (usually the discount) is taxed as ordinary income; the rest is capital gains. Better tax treatment applies if you hold for 2 years from the offering date and 1 year from purchase.

Example:

Your company offers a 15% discount and a lookback.

• Offering date price: $20
• Purchase date price: $28
• Purchase price: $17 (15% off the lower $20)
• Shares purchased: 1,000 at $17 = $17,000 total

You sell at $30 after meeting the holding periods.

• Ordinary income: lesser of (15% x $20 x 1,000 = $3,000) or the actual gain ($30 - $17 = $13 x 1,000 = $13,000). Result: $3,000 ordinary income.
• Capital gains: $13,000 total gain - $3,000 ordinary = $10,000 long-term capital gains.

How is each equity type taxed at grant, vesting, exercise, and sale?

The table below maps the tax treatment of each equity type across its life cycle. In short, nothing is taxed at grant; RSUs are taxed at vesting; NSOs and ISOs are taxed at exercise (ISOs only for AMT); and the final character at sale depends on whether you meet the holding-period rules.

Why does planning ahead reduce your equity tax bill?

The choices you make about when to exercise, hold, or sell determine how much of your equity is taxed at higher ordinary rates versus lower long-term capital gains rates. Planning ahead also lets you avoid a surprise AMT bill and keep withholding aligned with your real liability. Specifically, planning ahead helps you:

• Lower your tax rate by converting income that would be taxed at higher ordinary rates into income taxed at lower long-term capital gains rates.
• Avoid triggering AMT by knowing how much you can exercise without crossing the threshold.
• Prevent unexpected tax bills by making sure withholding and estimated payments match your real liability.
• Spread your income over multiple years to avoid stacking too much income in one year, which could push you into a higher tax bracket and increase your overall tax rate.
• Plan cash flow so you have the money to cover taxes without selling more stock than you want to.
• Minimize penalties and interest by making proactive estimated tax payments when needed.
• Leverage advanced tax strategies like real estate losses, Qualified Opportunity Zone deferrals, and capital loss harvesting to offset gains.

How do you build an equity compensation tax plan?

A sound equity plan models the tax impact before you act, times transactions across tax years, and keeps estimated payments aligned so you are never surprised in April. The most valuable steps are:

• Model the tax impact before you exercise or sell so you know exactly what you will owe and when.
• Time transactions strategically to spread income across multiple tax years and lower your overall rate.
• Avoid under-withholding penalties and interest by calculating your true tax liability at each stage and adjusting withholding or estimated payments.
• Manage AMT exposure by running scenario analysis on ISO exercises and recovering AMT credits in future years.
• Coordinate your equity plan with your full financial picture through year-round tax planning, including retirement planning, charitable giving, and investment strategy.

Your equity can be one of your most valuable assets, but the tax rules are complex, and the right plan is what lets you keep more of the gains. For founders and early employees, equity strategy also intersects with QSBS planning under Section 1202.

Have questions about how your RSUs, ISOs, NSOs, or ESPP will be taxed? Contact TS CPA for a free consultation. We respond within the same day.