When you exercise nonqualified stock options, or NQSOs, the bargain element is generally treated as wage income rather than immediately becoming capital gain. That means your employer may withhold federal income tax, Social Security tax, Medicare tax, and applicable state or local taxes through payroll. The important catch is that the amount withheld may be very different from the federal income tax you ultimately owe.
For most employees, the practical question is therefore not simply, "How much tax will payroll take?" It is, "Will payroll withholding be enough for my total tax bill after the option exercise?"
For a typical NQSO without a readily determinable market value at grant, taxable compensation is generally the stock's fair market value at exercise minus the exercise price. The employer reports that compensation as wages. Federal income tax withholding may use the supplemental-wage rules, but that withholding percentage is not necessarily your final income-tax rate.
What Part of an NQSO Exercise Is Taxed?
The IRS distinguishes nonstatutory, or nonqualified, stock options from statutory options such as incentive stock options. According to the IRS guidance on stock options, most nonstatutory options do not have a readily determinable fair market value when they are granted. In that common situation, exercising the option creates taxable compensation.
The basic calculation is:
Consider this illustrative scenario:
- Options exercised: 1,500 shares
- Exercise price: $20 per share
- Fair market value at exercise: $60 per share
- Spread: $40 per share
The compensation income would be:
$40 × 1,500 = $60,000
That $60,000 is not merely an unrealized stock gain for payroll purposes. It is generally compensation income associated with the exercise.
The IRS Employer's Tax Guide to Fringe Benefits states that an employer reports the excess of the stock's fair market value over the amount paid for a nonstatutory stock option in Form W-2 boxes 1, 3 up to the Social Security wage base, and 5, as well as box 12 using code V.
How Federal Income Tax Withholding Works
Income recognized from exercising a nonstatutory stock option is treated as supplemental wages under federal withholding regulations. That matters because payroll may calculate withholding differently from an ordinary paycheck.
For 2026, IRS Publication 15 says the optional flat federal withholding rate on qualifying supplemental wages remains 22%. When an employee's supplemental wages from an employer exceed $1 million during the calendar year, the portion above the applicable $1 million threshold is generally subject to mandatory withholding at 37%.
The employer does not always have to use the 22% method. Depending on how the payment is processed and whether the regulatory requirements are met, payroll can instead use the aggregate method, combining supplemental compensation with regular wages to calculate withholding.
| Payroll situation | Possible federal withholding treatment |
|---|---|
| NQSO compensation separately identified and flat-rate conditions met | Employer may generally use 22% on supplemental wages up to the applicable $1 million threshold |
| Supplemental compensation aggregated with regular payroll | Withholding may be calculated using the aggregate payroll method |
| Supplemental wages exceed $1 million for the year | Excess is generally subject to the mandatory highest-rate withholding rule, 37% for 2026 |
Why 22% does not mean your tax rate is 22%
This is where NQSO exercises can surprise employees.
A 22% withholding rate is a payroll collection mechanism. It is not a promise that the compensation will ultimately be taxed at 22%. Your final federal income-tax liability depends on your total taxable income, deductions, credits, filing status, and other items on your tax return.
If a large option exercise pushes more of your income into higher marginal brackets, 22% withholding can leave a balance due. Conversely, someone's overall effective tax rate could be lower than the withholding percentage.
Social Security and Medicare Also Matter
The federal income-tax line is only one piece of the payroll deduction.
For 2026, the employee Social Security tax rate is 6.2%, with a Social Security wage base of $184,500. Medicare tax is generally 1.45% for the employee and has no comparable wage ceiling. The current rates are explained in IRS Topic No. 751 on Social Security and Medicare withholding.
This means the Social Security effect of an NQSO exercise depends heavily on how much Social Security-taxable compensation you already received earlier in the year.
Example: $60,000 NQSO spread
Return to the illustrative $60,000 option spread. Assume for the moment that the entire amount remains below the Social Security wage base and that the employer uses 22% federal supplemental-wage withholding.
| Item | Illustrative amount |
|---|---|
| NQSO compensation income | $60,000 |
| Federal income-tax withholding at 22% | $13,200 |
| Employee Social Security at 6.2% | $3,720 |
| Employee Medicare at 1.45% | $870 |
| Illustrative federal payroll withholding | $17,790 |
This illustration excludes state and local taxes, Additional Medicare Tax, and any special payroll circumstances. It also assumes that all $60,000 remains subject to Social Security tax. Those assumptions may not match your exercise.
What if you already reached the Social Security wage base?
Suppose your Social Security wages before the exercise already equal or exceed the 2026 wage base. Additional NQSO compensation generally would not create another 6.2% employee Social Security deduction above that annual wage limit.
If you were only partly through the wage base, Social Security tax would generally apply only until the annual limit is reached.
Medicare works differently. There is no general Medicare wage ceiling.
Watch the Additional Medicare Tax Threshold
An employer must also withhold an additional 0.9% Medicare tax when Medicare wages it pays to an employee exceed $200,000 during the calendar year.
The payroll threshold is based on wages from that employer and does not change according to the employee's filing status. However, the employee's ultimate Additional Medicare Tax liability can depend on filing status. The IRS explains that the tax-return thresholds are $250,000 for married filing jointly, $125,000 for married filing separately, and $200,000 for other taxpayers.
That difference can create either additional tax due or a reconciliation on the tax return. See the IRS Additional Medicare Tax guidance for the filing-status rules.
Where the NQSO Exercise Appears on Form W-2
After the exercise, check your Form W-2 carefully rather than looking only at the brokerage statement.
Under the IRS instructions for Forms W-2 and W-3, income from exercising nonstatutory stock options is reported using Code V in box 12. The spread is also generally included in:
- Box 1: wages, tips, and other compensation;
- Box 3: Social Security wages, subject to the annual wage-base limit; and
- Box 5: Medicare wages and tips.
This is especially important if you exercised options from a former employer. A former employer may still issue a W-2 reflecting compensation from an NQSO exercise.
Exercise Tax and Stock-Sale Tax Are Two Different Layers
Exercising an NQSO and later selling the acquired stock can create two separate tax events.
The compensation spread recognized at exercise generally becomes part of your tax basis in the acquired shares. For a typical option without readily determinable value at grant, basis will generally reflect the exercise price plus the compensation amount already included in income.
After exercise, further movement in the stock price can create capital gain or loss when you sell.
For example, suppose you exercise at a $60 fair market value and recognize $40 per share of compensation because the strike price is $20. If you later sell the stock at $72, the later economic increase is generally $12 per share rather than the full $52 difference between the $20 exercise price and $72 sale price.
This distinction helps prevent an easy tax-reporting mistake: effectively treating compensation already taxed through payroll as capital gain a second time.
The IRS warns in Publication 525 that basis information reported on Form 1099-B for certain option shares may not include compensation previously included in income. The taxpayer may therefore need to make an appropriate basis adjustment on Form 8949.
How to Tell Whether Payroll Withholding May Be Too Low
Before exercising a significant number of options, estimate the entire year's tax picture rather than comparing only the option spread with the payroll withholding percentage.
- Estimate your regular wages for the full year.
- Add the expected taxable spread from all planned NQSO exercises.
- Add other significant taxable income, such as bonuses, investment income, business income, or a spouse's income on a joint return.
- Estimate deductions and credits.
- Compare projected total federal tax with withholding already paid plus expected future withholding.
- If a gap remains, consider additional payroll withholding or estimated tax payments.
A particularly large option exercise can make this calculation worthwhile even when payroll withholds thousands of dollars at exercise. A large withholding number is not necessarily an adequate withholding number.
Could You Need Estimated Tax Payments?
Possibly. The answer depends on your total expected tax and how much has already been paid through withholding and credits.
For 2026, IRS Publication 505 generally says estimated tax may be required when you expect to owe at least $1,000 after withholding and credits and those payments are expected to fall below the applicable required-payment threshold.
A commonly used federal safe-harbor framework compares payments with the smaller of:
- 90% of the tax expected to be shown on the current-year return; or
- 100% of the tax shown on the prior-year return, assuming that return covered 12 months.
For certain higher-income taxpayers, the prior-year percentage generally becomes 110% rather than 100%. Special rules and exceptions can apply.
That does not mean everyone exercising NQSOs should automatically make an estimated payment. You might instead be able to increase federal income-tax withholding from future wages. The better choice depends on timing, other income, your prior-year return, and the size of the exercise.
Five Questions to Ask Before Exercising NQSOs
- What fair market value will payroll use? The spread depends on the stock value used at exercise.
- How will federal withholding be calculated? Ask whether payroll expects to use the supplemental flat-rate method or another permitted method.
- How much Social Security wage base remains? This can materially change the cash needed for payroll tax.
- Will the exercise cross the $200,000 Additional Medicare withholding threshold? Check year-to-date Medicare wages.
- Will total withholding cover your projected annual tax? The payroll percentage alone cannot answer this question.
A Simple Exercise Decision Framework
| Situation | What to check first |
|---|---|
| Small exercise relative to salary | Verify withholding and W-2 treatment |
| Large exercise pushes annual income sharply higher | Model projected total tax, not just the 22% withholding amount |
| Year-to-date wages near $184,500 | Determine how much of the spread remains subject to Social Security tax |
| Year-to-date wages near $200,000 | Check Additional Medicare withholding |
| Planning to hold shares after exercise | Consider concentration risk, cash required for taxes, and later capital gain or loss |
Bottom Line
Nonqualified stock options can create a surprisingly large payroll event because the exercise spread is generally treated as compensation. Federal income-tax withholding may be calculated under the supplemental-wage rules, while Social Security, Medicare, Additional Medicare Tax, and state or local withholding can further reduce the cash or shares you receive.
The number to watch most closely is not simply the withholding percentage. Compare your projected full-year tax with all taxes already withheld. If the NQSO exercise is large relative to your normal compensation, reviewing the numbers before exercising can be much easier than discovering a substantial shortfall when you file your return.
This article is for general educational purposes and does not provide individualized tax, financial, legal, or investment advice. Equity-compensation plans, payroll practices, state tax rules, and individual tax circumstances vary. For a material option exercise, consider confirming the exercise and withholding treatment with your employer's payroll or stock-plan administrator and a qualified tax professional.
