Founders can owe tax on startup equity before they can sell it. The first step is to identify what they own—restricted stock, incentive stock options (ISOs), or nonstatutory stock options—then map each grant, vesting, exercise, and sale date to its tax treatment. For federal planning, model the tax bill alongside the cash needed to exercise and the possibility that private shares remain illiquid. State and local tax, company-specific eligibility, and transfer restrictions require separate review.
Start with the equity instrument and its tax events
Similar-looking equity can produce different tax results. Gather the grant or purchase agreement, vesting schedule, exercise and transfer records, exercise price, company fair-market-value information, sale or tender-offer documents, Forms 3921 or 3922 if applicable, W-2s, and prior returns. The dates and amounts help distinguish compensation income, an alternative minimum tax (AMT) adjustment, and capital gain or loss.
| Equity | Event to examine | Federal tax planning point |
|---|---|---|
| Restricted stock or other qualifying restricted property | Transfer of the property and subsequent vesting | Without an 83(b) election, income may generally be recognized as restrictions lapse. A valid election can change the timing; it applies to qualifying property, not to a nonstatutory option. See IRS Publication 525 (2025). |
| ISO | Exercise, the point when shares become transferable or are no longer subject to a substantial risk of forfeiture, and eventual sale | Exercise may create an AMT adjustment even when regular income tax is not due at exercise. Sale treatment depends on statutory holding periods. See IRS Publication 525 (2025) and IRS Topic 556. |
| Nonstatutory stock option | Exercise and later sale | In common cases, the spread at exercise is compensation income; the later sale is a separate tax event. Review reported basis because Form 1099-B may not reflect income already included. See IRS Publication 525 (2025) and IRS Topic 427. |
For ISOs, the company generally provides Form 3921 with important exercise dates and values. Keep it with the grant and exercise records. For a nonstatutory option, compare the broker’s reported basis with the amount previously included as compensation; an adjustment may be needed on Form 8949 to avoid taxing the same amount twice.
Model an ISO exercise with both tax systems and cash flow
Do not equate “no regular income tax at exercise” with “no tax exposure.” For AMT purposes, the spread—the share value used for tax purposes minus the exercise price—can be an adjustment when the shares’ rights become transferable or they are no longer subject to a substantial risk of forfeiture. The timing depends on the facts. The IRS notes that “Your AMT basis in stock acquired through the exercise of an ISO is likely to differ from your regular tax basis.” Keep separate records for each basis.
Before exercising, compare the cash required to pay the exercise price and any potential tax with the possibility that you cannot sell the shares promptly. A later decline in value or delayed liquidity can leave you with a tax bill and little cash to pay it. Model more than one outcome rather than relying on a single forecast:
- Exercise now or wait, accounting for the exercise cost, current value information, and possible AMT.
- Hold the shares or sell some if a permitted sale or tender offer is available.
- Compare an outcome in which the shares qualify for QSBS treatment with one in which they do not.
- Check how much cash remains available for tax after any exercise, rather than treating paper value as spendable money.
For an ISO sale to receive the ordinary tax treatment associated with a qualifying disposition, the shares generally must be held until the later of one year after transfer or two years after the grant date. Selling before satisfying both periods can be a disqualifying disposition with different income treatment. Do not assume every gain on ISO shares is long-term capital gain; see IRS Publication 525 (2025).
Consider an 83(b) election only for qualifying restricted property
An 83(b) election can cause the value of qualifying restricted property to be included in income in the year it is transferred, rather than as restrictions lapse later. That timing choice can matter when the property’s value is low at transfer and may rise, but it can also accelerate tax on property that later loses value or is forfeited. It is not an election for a nonstatutory option.
The IRS describes election-statement information including the taxpayer’s identity, the property, transfer date, restrictions, fair market value, and amount paid. Because the election is deadline-sensitive and the filing steps matter, verify the current IRS instructions and filing procedure before acting; do not rely on a generic checklist or assume an option grant qualifies. The relevant IRS discussion is in Publication 525 (2025).
Check whether the shares may qualify as QSBS
Qualified small business stock (QSBS) treatment is not automatic just because a company is a startup. The issuer and the particular shares must meet the applicable requirements. The IRS’s 2025 Schedule D instructions describe qualified stock as stock in a domestic C corporation, originally issued after August 10, 1993, with gross-asset and active-business tests. They state a $50 million gross-asset threshold for stock issued on or before July 4, 2025, and $75 million for stock issued after that date; certain businesses are excluded from the qualified-business definition. Company records and a tax professional familiar with the issuer’s circumstances are needed to assess eligibility. See the 2025 Instructions for Schedule D (Form 1040).
Acquisition date matters because section 1202 changed in 2025. IRS 2025 Schedule D instructions describe older rules, including a more-than-five-year holding period and acquisition-date-based exclusion percentages. Separate IRS explanatory material says stock acquired after July 4, 2025 may qualify for up to a 100% exclusion after at least five years and describes a $15 million per-issuer excluded-gain limit. These materials do not present every transition rule in one harmonized place. Do not apply an older rule or a new-law summary to a grant or share without checking the law and guidance applicable to that specific stock and event. See the IRS explanation of the 2025 business tax provisions alongside the Schedule D instructions.
For some qualifying QSBS, section 1045 may allow gain deferral when stock held for more than six months is replaced with qualifying stock within 60 days, subject to active-business, filing, and other conditions. It is a conditional rollover, not automatic tax elimination. See IRS Publication 550 (2025).
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Plan when the tax is paid, not just how much
Tax due from compensation, an AMT adjustment, or a sale may arise before private shares can be converted to cash. Federal income tax generally must be paid during the year through withholding or estimated payments. The IRS says individuals generally may need estimated payments if they expect to owe at least $1,000 when filing, subject to exceptions; safe harbors and special rules can change the calculation, including for higher-income taxpayers or uneven income. Use current forms and update the estimate after an exercise, sale, or other major income event. See the IRS estimated-tax guidance.
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Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Before a major equity event, have a CPA or tax attorney with startup-equity experience review the instrument, dates, basis records, possible QSBS status, and payment schedule. The right analysis depends on the exact shares and facts; no general rule can determine whether exercising, holding, or selling is best for every founder.
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