What this ISO sale calculator answers
This calculator follows one identified lot of ordinary corporate stock acquired through a supported Internal Revenue Code Section 422 incentive stock option and sold, or planned for sale, during calendar year 2026. It uses the grant, exercise, and sale trade dates to classify the sale as a qualifying or disqualifying disposition. It then estimates regular-tax ordinary compensation, regular-tax adjusted basis, the remaining short- or long-term capital result, and a separate AMT capital result when the exercise occurred in a prior year.
The separation matters because the same shares can have two tax bases. Regular-tax basis commonly starts with the exercise cost and increases by compensation recognized on a disqualifying disposition. AMT basis for shares carried beyond the exercise year generally includes the ISO adjustment previously entering alternative minimum taxable income. A broker’s Form 1099-B does not perform that complete two-system reconciliation. This tool makes the records visible but does not prepare Form 1040, Form 8949, Schedule D, Form 6251, Form 8801, a state return, or an employer correction.
Confirm Section 422 ISO status before calculating
IRS Topic 427 distinguishes incentive stock options and employee stock purchase plan options as statutory options when their legal requirements are met. An ISO label in an equity portal is not enough. The grant agreement, plan, employment history, exercise timing, corporate records, and Form 3921 must support ISO treatment. An option can instead be wholly or partly nonstatutory, and the ordinary-income timing then changes.
The supported path assumes the user was the employee and original purchaser; one Form 3921 lot is specifically identified; rights in the stock were transferable and no longer subject to a substantial risk of forfeiture at exercise; no separate amount was paid for the option; and the shares were sold in an ordinary arm’s-length taxable trade during 2026. Stop for restricted shares, post-termination qualification questions, Section 83(b) or 83(i), option transfers, gifts, death, corporate actions, hedges, tender or installment transactions, multiple unidentified lots, or residence and work spanning jurisdictions.
The IRS Instructions for Forms 3921 and 3922 identify the core ISO records: Form 3921 box 1 is the grant date, box 2 the exercise date, box 3 the exercise price per share, box 4 exercise-date FMV per share, and box 5 shares transferred. Match the form with the exercise confirmation and lot ledger. Do not replace a missing historical FMV with the 2026 sale price or a current quote.
Two statutory clocks classify the ISO disposition
IRS Publication 525 says the holding requirement is satisfied when the stock is not sold until the end of the later of the one-year period after the stock was transferred to the employee or the two-year period after the option was granted. The property holding period begins the day after exercise. This calculator finds both anniversaries and treats the day after the later boundary as the first supported qualifying-disposition date.
For example, suppose an ISO was granted March 12, 2023, exercised January 7, 2024, and sold January 27, 2025. More than one year passed after exercise, but two years had not passed after grant. Publication 525 classifies that sale as disqualifying. A sale can therefore be disqualifying yet still have a long-term capital component. The statutory ISO label and the capital holding-period label answer different questions.
On an ordinary supported qualifying disposition, the sale necessarily occurs after the one-year exercise boundary, so its regular capital result is long term. A sale on an anniversary boundary is not yet after the end of that period; the first qualifying date is the next day. The calculator displays that date instead of asking the user to count days manually.
Qualifying ISO sales have no regular compensation component
When both statutory periods are satisfied, Publication 525 says gain or loss from the ISO stock sale is capital and regular-tax basis is the amount paid for the shares. Under this calculator’s path, regular ordinary compensation is zero, starting and adjusted regular basis equal shares multiplied by the exercise price, and the net amount realized minus that basis is long-term capital gain or loss.
Assume 100 shares were exercised for $10 each and later sold in a qualifying disposition for $30 each with no selling expenses. Regular exercise cost and basis are $1,000, net proceeds are $3,000, ordinary compensation is zero, and the regular long-term capital gain is $2,000. Exercise-date FMV does not change the qualifying regular basis, but it still matters to the prior exercise-year AMT basis record.
Disqualifying ISO sales divide gain between wages and capital
When either statutory period is not satisfied and the sale has a gain, Publication 525 treats ordinary income as the sale gain up to the positive exercise spread. The exercise spread is exercise-date FMV minus exercise price, multiplied by the shares. The tool compares that spread with the positive net gain measured from exercise cost and uses the smaller amount. Any gain remaining after basis is increased by ordinary income is capital gain.
Publication 525’s example uses 100 shares exercised at $10 when FMV was $12 and later sold for $15. Total gain before character is $500, the exercise spread is $200, ordinary compensation is $200, regular adjusted basis becomes $1,200, and the remaining capital gain is $300. If the same shares instead produce only $100 of net gain, ordinary income is limited to $100 and no capital gain remains. This gain limit is different from the ESPP disqualifying formula.
If net amount realized is below exercise cost, the disposition has a regular capital loss and no ISO ordinary income under the Publication 525 rule. Selling expenses reduce amount realized and can therefore affect a disqualifying disposition’s positive-gain limit. The result flags every modeled capital loss for a separate wash-sale review.
Regular-tax adjusted basis prevents double taxation
For a supported disqualifying disposition, regular adjusted basis equals exercise cost plus ordinary compensation recognized for that sale. The capital result is net amount realized minus that adjusted basis. Adding the wages once prevents the same part of the economic gain from appearing both in wage income and again in capital gain.
When an incorrect broker basis was reported to the IRS
Publication 525 says the taxpayer is responsible for appropriate basis adjustments reported through Form 8949. The IRS Instructions for Form 8949 say that when an incorrect basis was reported to the IRS, the taxpayer keeps the reported amount in column (e), uses code B, and enters the correction in column (g). The basis-only correction is reported basis minus modeled correct regular basis. Other transaction adjustments can change the final code and entry.
When basis was not reported to the IRS
If basis was not reported to the IRS, the Form 8949 instructions generally use correct regular basis in column (e) and zero in column (g) for the basis issue alone. The optional last step reports this workflow separately. It never places AMT basis into the regular Form 1099-B comparison.
Exercise year determines the AMT sale path
The IRS Instructions for Form 6251 say no ISO exercise adjustment is required when stock is acquired by exercising the ISO and disposed of in the same year; regular and AMT treatment of that same-year sale is the same. The calculator therefore sets the modeled exercise-year line 2i amount to zero and mirrors the regular disposition result for AMT when the entered exercise and sale dates are both in 2026.
When a supported ISO lot was exercised before 2026 and carried into 2026, the earlier exercise-year adjustment generally increased AMT basis. Under this page’s narrow no-restriction path, the modeled prior-year adjustment allocated to the sold shares is the positive exercise-date spread. Modeled AMT basis is exercise cost plus that adjustment, which is the exercise-date FMV multiplied by shares when FMV exceeds the exercise price.
The prior-year AMT sale result uses net amount realized minus modeled AMT basis. It does not include the ISO ordinary compensation used for regular tax. The result can therefore show regular wages and a regular capital gain while the AMT column shows a capital loss, as in the Form 6251 instructions’ ISO example.
The displayed AMT difference is not final Form 6251 line 2k
The calculator displays the raw difference between total modeled AMT disposition income and total modeled regular-tax disposition income before capital-loss limits and the rest of the return. For a supported prior-year lot, that raw difference commonly reverses the prior positive ISO adjustment allocated to the sold shares. It is a reconciliation clue, not a filing instruction.
Form 6251 line 2k requires capital gains and losses to be refigured under AMT basis, including a separate AMT Schedule D and separate capital-loss limitation and carryover when applicable. Other dispositions and adjustments can change the line. Do not copy the raw difference directly to Form 6251 without completing the current instructions and both capital-gain computations.
An ISO sale does not automatically refund prior AMT
A lower AMT gain or larger AMT loss in the sale year can reduce alternative minimum taxable income, but it does not by itself establish a cash refund or a usable credit. The IRS Instructions for Form 8801 use the complete prior-year and current-year tax records to determine any minimum tax credit and carryforward. Whether prior AMT created a deferral credit, how much remains, and how much current regular tax permits are separate questions.
Preserve the exercise-year Form 6251, all prior Forms 8801, the regular and AMT lot bases, and partial-disposition records. A 2026 sale may be the event that makes part of a credit usable, but a sale-price calculator cannot prove that result without the full returns.
Form W-2 income may arrive without withholding
Publication 525 says an employer or former employer should report ordinary income from a disqualifying ISO disposition as wages in Form W-2 box 1. If the form is not provided or omits the amount, Publication 525 describes a separate Schedule 1 wage-reporting route. Reconcile the calculator’s estimate with the employer disposition statement and the final wage form; do not include the amount twice or silently omit it.
2026 IRS Publication 15-B says statutory-option remuneration from exercise or disposition is excluded from Social Security, Medicare, and FUTA wages, and federal income tax withholding is not required on disqualifying-disposition income. It also says the ISO exercise spread is reported in Form W-2 box 1 for a disqualifying disposition. Consequently, a substantial wage amount can appear without matching federal withholding, creating a projected balance due or estimated-payment need.
Do not run ISO disposition wages through the 2026 NSO Exercise Tax and Withholding Calculator. That tool models an ordinary employee NSO exercise with Code V wage and payroll withholding assumptions. Use the 2026 Quarterly Estimated Tax Calculator only after the complete projected total tax, withholding, and payments are established.
A capital loss requires a wash-sale review
IRS Publication 550 explains that a stock loss can be disallowed when substantially identical stock or securities are acquired during the period beginning 30 days before and ending 30 days after the sale. ISO or NSO exercises, RSU settlements, ESPP purchases, dividend reinvestment, spouse activity, and transactions in another account can matter.
The calculator stops before arithmetic when a wash-sale issue is already known. If a supported calculation unexpectedly produces either a regular or AMT capital loss, the result also flags the 61-day review. Regular and AMT wash-sale basis and loss records may differ; this page does not allocate a disallowed loss to replacement shares.
Use trade dates and preserve the exact lot
Publication 550 explains that the holding period for property acquired by exercising an option begins the day after exercise. For exchange-traded securities, use the sale trade date rather than settlement date. Preserve the accepted specific-lot instruction and broker confirmation; a performance chart or a default FIFO display does not prove which Form 3921 lot was sold.
Keep grant date, exercise date, shares, exercise price, exercise-date FMV, exercise-year line 2i adjustment, regular basis, AMT basis, sale date, gross proceeds, selling expenses, employer compensation, Form 1099-B basis, and every later adjustment. When only part of a Form 3921 lot is sold, allocate records consistently to the identified shares and retain the remainder’s dual bases.
What the calculator deliberately excludes
The result does not determine whether the option legally qualified as an ISO, whether any portion exceeded statutory limits, whether Form 3921 is correct, which shares were sold, whether an employment-status deadline was met, whether stock was substantially vested, or whether a transaction is an ordinary sale. It excludes gifts, inheritance, death, conflict-of-interest dispositions, Section 83(b) and 83(i), separate option cost, replacement shares, corporate actions, return of capital, constructive sales, hedges, tender transactions, installment treatment, short sales, and unidentified or averaged lots.
It also excludes final ordinary income tax, preferential capital-gain tax, AMT exemption and rates, exact Form 6251 line 2k, AMT capital-loss limitation, Form 8801 credit, net investment income tax, withholding, safe-harbor penalties, state or local tax, nonresident and cross-border sourcing, currency conversion, community property, payroll corrections, investment advice, and whether shares should be held or sold. Use the 2026 Alternative Minimum Tax Calculator only after complete AMTI and regular-tax inputs are established, and use the 2026 Long-Term Capital Gains Tax Calculator only with verified eligible return-level amounts.
A practical 2026 ISO sale workflow
- Confirm Section 422 ISO status through exercise from the grant, plan, employment, and exercise records.
- Match Form 3921 to the exact shares sold; do not average several exercise lots.
- Use the grant, exercise, and sale trade dates to test both statutory clocks.
- Calculate regular ordinary income under the qualifying or disqualifying branch.
- Add any regular compensation to exercise cost once when establishing regular basis.
- Reconcile employer disposition reporting and Form W-2 box 1 without assuming withholding occurred.
- Compare regular basis with Form 1099-B and the correct Form 8949 reporting category.
- Trace the exercise-year Form 6251 adjustment and maintain a separate AMT basis.
- Refigure the 2026 AMT capital result and complete Form 6251 with the rest of the return.
- Review Form 8801 separately when prior AMT or a minimum-tax-credit carryforward exists.
- Check the 61-day wash-sale window whenever either tax system produces a loss.
The 2026 Stock Compensation Tax Guide connects this sale with the earlier 2026 ISO AMT Adjustment Calculator, complete-return tax, payments, basis records, and employer-stock concentration risk. Treat exercise, sale, AMT, and credit recovery as connected records but separate computations.
Official sources and 2026 limitations
The ISO classification, ordinary-income formula, regular basis, and wage reporting follow IRS Publication 525. Form 3921 fields follow the current Instructions for Forms 3921 and 3922. Same-year disposition and prior-year AMT basis treatment follow the current Instructions for Form 6251. Statutory-option payroll and withholding treatment follows 2026 Publication 15-B. The regular broker-basis workflow follows the current Instructions for Form 8949, while the credit warning follows the Instructions for Form 8801.
Some individual-return publications and forms for tax year 2026 may be revised after this page’s July 28, 2026 review. Current law, final 2026 forms, option documents, employer records, brokerage reporting, and the user’s complete facts control. Recheck official instructions before filing the 2026 return in 2027.
This calculator provides educational U.S. federal arithmetic for one narrowly supported Section 422 ISO stock lot sold or planned for sale in 2026. It is not tax preparation, tax, legal, accounting, payroll, valuation, investment, securities, equity-compensation, or financial advice. It does not determine ISO qualification, lot identity, substantial vesting, FMV, employer reporting, final tax, AMT, Form 6251 or 8801 entries, withholding, wash-sale allocation, state or foreign sourcing, penalties, or whether to sell or hold employer stock. Verify every input and result with the grant and plan, Form 3921, exercise-year returns, employer, broker, current IRS forms and instructions, return software, and qualified guidance. Official sources were accessed July 28, 2026.