Stock Option Tax Calculator: ISO vs NSO Taxes (2026)
Calculate exercise cost and spread, then apply a planning tax rate. For NSOs, the spread is generally compensation income at exercise and usually subject to payroll taxes. ISOs generally create no regular federal income at exercise, but the spread can create an Alternative Minimum Tax (AMT) adjustment. This tool measures the spread; it does not perform a Form 6251 AMT calculation.
On this page: Calculator · NSO vs ISO comparison · How it works · FAQs
Stock option tax calculator
Enter options, strike price, current fair market value, and a planning tax rate to see exercise cost, spread, estimated tax on the spread, and net spread after tax.
For an NSO scenario, use a planning rate reflecting federal income tax, applicable payroll tax, and state/local tax. For an ISO, use this primarily to measure the spread: AMT is a separate calculation and cannot be estimated reliably by substituting your regular marginal rate.
Exercise cost: $
Exercise spread: $
Estimated tax on spread: $
Net spread after estimated tax: $
Planning tax rate applied: %
Large option exercises can create W-2, Form 3921, Form 6251, and brokerage-basis questions. For professional filing help, H&R Block↗ is one option. Affiliate link — we may earn a commission at no cost to you.
NSO vs ISO tax comparison (2026)
Start with the spread: number of shares × (fair market value at exercise − strike price). The same spread can be treated very differently depending on whether the option is an NSO or ISO.
| Event | NSO / NQSO | ISO |
|---|---|---|
| Grant | Usually no tax for a typical employee option without readily determinable FMV | No regular income at grant |
| Exercise | Spread is generally compensation income reported as wages | No regular federal income; spread can be an AMT adjustment |
| Social Security / Medicare | Generally applies to employee NSO exercise compensation | Remuneration from ISO exercise/disposition is generally excluded from these wages |
| Later sale | Gain/loss after exercise is capital, using adjusted basis | Qualifying sale is generally capital gain; disqualifying sale can create ordinary compensation plus capital gain/loss |
| Key form | W-2 may report exercise spread with code V; sale may require basis adjustment | Form 3921 provides exercise data; Form 6251 may be relevant for AMT |
A qualifying ISO disposition generally requires holding until the later of one year after stock transfer at exercise and two years after grant. If ISO shares are disposed of in the same tax year they are exercised, an ISO exercise AMT adjustment is generally not required.
How stock option taxes work (2026)
NSO (Non-Qualified Stock Options)
For a typical employee NSO without a readily determinable value at grant, exercise creates compensation income equal to the spread between fair market value and strike price. The employer generally reports the spread on Form W-2, including code V in box 12, and the amount is generally subject to federal income-tax withholding plus Social Security and Medicare taxes.
After exercise, tax basis includes the exercise price plus compensation already included in income. IRS Publication 525 warns that Form 1099-B basis for stock acquired through option exercise may not include compensation previously taxed, so review Form 8949 basis before calculating the later capital gain or loss.
ISO (Incentive Stock Options)
ISO exercise generally creates no regular federal income, and remuneration from exercising or disposing of statutory-option stock is generally excluded from Social Security and Medicare wages. For AMT, however, the spread can be an adjustment when the stock becomes transferable or is no longer subject to substantial risk of forfeiture. No ISO exercise adjustment is generally required if the shares are disposed of in the same year as exercise.
To preserve qualifying-disposition treatment, you generally must wait until the later of one year after stock transfer at exercise and two years after grant. A disqualifying disposition can create ordinary compensation income, but the amount is not always identical to the exercise-date spread; sale price and other facts matter.
2026 AMT reference for ISO exercises
The calculator above does not calculate AMT. For 2026, the federal AMT exemption is $90,100 for unmarried individuals and $140,200 for joint filers. The exemption phaseout begins at $500,000 for unmarried individuals and $1,000,000 for joint filers. AMT depends on the taxpayer’s full alternative minimum taxable income — not simply the ISO spread multiplied by 26% or 28%.
Early ISO exercise and an 83(b) election
If an ISO is exercised before the acquired shares are vested, a Section 83(b) election can be relevant for AMT purposes. It does not replace the regular-tax ISO rules. The IRS provides Form 15620 for a Section 83(b) election, and the election generally must be filed no later than 30 days after the property transfer. Early exercise also adds forfeiture and liquidity risk.
For the broader equity picture, see the equity compensation hub or RSU tax calculator.
Official stock-option tax sources
See IRS Topic 427 and IRS Publication 525 for ISO/NSO treatment and basis rules. The 2026 AMT amounts are in IRS Revenue Procedure 2025-32. For early-exercised unvested stock, see IRS Form 15620.
Filing taxes with stock options?
Depending on option type and transactions, reporting can involve W-2 income, Form 3921, Form 6251, Form 8949, and Schedule D. Check current product support for the forms you need:
TurboTax↗ — tax-filing software option for returns with compensation and investment income
H&R Block↗ — professional-help option for large ISO exercises or AMT questions
FreeTaxUSA↗ — lower-cost filing option; verify current support for your equity forms
Affiliate links — we may earn a commission at no cost to you.
Related calculators
- RSU tax calculator Estimate RSU vest value and review 2026 supplemental-withholding and FICA rules
- Capital gains tax calculator Estimate tax when selling stock option shares — short and long-term rates
- Take-home pay calculator See how NSO exercise income stacks with your salary for total W-2 tax planning
- Marginal vs effective tax rate How NSO exercise income pushes combined income into higher brackets
Stock option tax calculator: FAQs
How are NSO stock options taxed?
In the typical employee NSO case, exercising the option creates ordinary compensation income equal to fair market value minus exercise price. The employer generally reports that spread as W-2 wages, and Social Security and Medicare taxes usually apply. A later sale creates a separate capital gain or loss using adjusted basis.
How are ISO stock options taxed?
Exercising an ISO generally creates no regular federal income, but the exercise spread can be an AMT adjustment. A qualifying sale generally requires holding until the later of one year after exercise and two years after grant. A sale that misses those holding periods is a disqualifying disposition and can create ordinary compensation income plus capital gain or loss.
What is the difference between ISO and NSO taxes?
NSOs generally create compensation income and employment taxes at exercise. ISOs generally avoid regular income and Social Security/Medicare wages at exercise, but the spread can affect AMT. ISO treatment at sale also depends on statutory holding periods, while post-exercise NSO appreciation is generally handled under normal capital-gain rules.
Do I owe taxes if I don't sell my stock options after exercising?
For NSOs, usually yes: exercise itself generally creates compensation income even if you keep the shares. For ISOs, there is generally no regular federal income at exercise, but the spread can create an AMT adjustment even while shares are held. The later stock sale is a separate tax event.
Why is my stock option tax so high?
A large NSO exercise can add substantial W-2 compensation to salary in one year. That can place part of the additional income in a higher federal or state marginal bracket, while Social Security and Medicare taxes may also apply. Payroll withholding is only a prepayment, so final tax should be projected using total annual income rather than the exercise spread alone.
Does this calculator include AMT?
No. The calculator measures the option spread and applies a user-entered planning tax rate; it does not calculate Form 6251. For 2026, the federal AMT exemption is $90,100 for unmarried individuals and $140,200 for joint filers, with phaseout beginning at $500,000 and $1,000,000 respectively. An actual ISO AMT calculation depends on full alternative minimum taxable income and other adjustments.
Can exercising stock options increase my tax bracket?
Yes. NSO exercise compensation stacks on top of salary and other taxable income in the exercise year. Because federal brackets are marginal, only the portion falling inside a higher bracket is taxed at that higher rate. ISO exercise can instead affect AMT even when it does not increase regular taxable income.
Is this calculator tax or financial advice?
No. This is a planning calculator, not a tax-return or AMT engine. Outcomes can depend on vesting restrictions, option type, exercise timing, sale price, basis reporting, state tax, and prior AMT. Consult a qualified tax professional before a material exercise or sale decision.