By Harry Prabandham · Updated September 27, 2026
Equity Compensation
Startup Stock Options: A Practical Guide for Employees
Startup options are rights to buy shares at a fixed strike price. Their value depends on vesting, taxes, exit windows, and whether the company succeeds.
Startup Stock Options: A Practical Guide for Employees
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What is a startup stock option?
- An option is the right to buy a set number of company shares at a fixed strike price, usually for up to ten years.
- The strike price is generally set at the 409A fair market value of common stock on the grant date.
- Options vest over time—often four years with a one-year cliff—and only vested options can be exercised unless early exercise is allowed.
- Your stake equals your shares divided by the fully diluted share count, a number many companies will share on request.
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Full Guide
What is a startup stock option?
- An option is the right to buy a set number of company shares at a fixed strike price, usually for up to ten years.
- The strike price is generally set at the 409A fair market value of common stock on the grant date.
- Options vest over time—often four years with a one-year cliff—and only vested options can be exercised unless early exercise is allowed.
- Your stake equals your shares divided by the fully diluted share count, a number many companies will share on request.
Why is the 409A price lower than the headline valuation?
- Headline valuations come from preferred stock sold to investors, which carries liquidation preferences and other rights.
- Common stock lacks those rights, so independent 409A appraisals usually value it well below the preferred price per share.
- The gap tends to narrow near an IPO or sale, when preferred stock typically converts to common.
- A 409A value is a tax-compliance appraisal, not a price anyone has agreed to pay.
How are ISOs and NSOs taxed?
- NSOs: the spread at exercise is ordinary income, with payroll withholding for employees; later growth is capital gain.
- ISOs: no regular income tax at exercise, but the spread counts toward alternative minimum tax if you hold the shares past year-end.
- ISO shares held two years from grant and one year from exercise qualify for long-term capital gains on the full gain.
- Selling ISO shares earlier is a disqualifying disposition, which turns part of the gain into ordinary income.
QSBS and startup shares
- Shares can qualify but options cannot, so the holding period starts when you exercise.
- For shares issued after July 4, 2025, up to the greater of $15 million or 10x basis may be excluded, with partial exclusions after three and four years.
- The company must be a qualifying C-corporation under the gross-asset limit and in an eligible business when the shares are issued.
- California does not follow the federal exclusion, so state tax can still apply.
What happens to options when you leave?
- Unvested options are usually forfeited when you leave.
- Many plans allow 90 days to exercise vested options, and ISOs lose ISO status after three months even if the plan allows longer.
- Exercising requires the strike price plus any tax on the spread, which can be large for long-tenured employees.
- Specialized option-financing arrangements exist; some are non-recourse but usually take a share of upside and charge fees.
Managing the risk
- Treating option value as uncertain, since many startups never reach an exit that returns value to common shareholders.
- Exercising in stages across tax years to spread AMT or income exposure, recognizing each exercise commits more cash to one company.
- Using tender offers or approved secondary sales for partial liquidity before an IPO, when available.
- Modeling a zero-value outcome alongside upside cases before committing savings to exercises.
Key takeaways
- Know your grant: share count, strike, vesting, option type, expiration, and exit window.
- ISOs and NSOs differ in when and how tax applies; timing can change the bill substantially.
- Exercising starts capital-gains and QSBS clocks but puts cash at risk in an illiquid stock.
- Confirm tax treatment with a CPA before exercising; Rubric does not prepare tax returns.
Related Topics
Equity Compensation
ISOs vs NSOs: How Stock Option Taxes Differ
NSO spreads are taxed as wages at exercise; ISO spreads skip regular tax but can trigger AMT, and qualify for long-term rates if holding periods are met.
Equity CompensationEarly Exercise and the 83(b) Election, Explained
Early exercise lets you buy unvested option shares now. An 83(b) election, due within 30 days, taxes them at today's value instead of at each vest.
Equity CompensationLeaving a Startup With Stock Options: The Exercise Deadline
When you leave a company, vested options usually expire unless exercised within a set window, often 90 days, and ISOs lose tax status after three months.