The short answer: An employee stock option gives you the right to buy company shares at a fixed strike price once the options vest, usually over four years with a one-year cliff. The strike price must be at least the fair market value of the common stock on the grant date, which private companies set with a 409A valuation. If options are granted below that value, the employee can face immediate tax plus a 20% additional federal tax, which is why a current, independent 409A valuation protects the team.
Stock options help companies attract talent by giving employees ownership and tying them to the company’s long-term success.
Key takeaways
- Right, not obligation: options let you buy shares at a fixed price; you choose whether and when.
- Vesting: the common schedule is four years with a one-year cliff, then monthly vesting.
- Strike price = fair market value: set from the company’s 409A valuation on the grant date.
- Discounted options are costly: tax as the options vest, plus 20% additional federal tax and interest.
- ISO vs NSO: ISOs can mean capital gains treatment but may trigger AMT; NSOs are taxed as income at exercise.
- Leaving: you usually have 90 days to exercise vested options; ISOs become NSOs after three months.
Why Founders Should Share This Guide
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What Are Employee Stock Options?
Employee stock options give you the right, but not the obligation, to buy a set number of company shares at a fixed strike price once they vest. If the company grows and its shares become worth more than the strike price, you share in that gain.
There are two main types, incentive stock options (ISOs) and non-qualified stock options (NSOs), and they are taxed very differently. Our guide to the difference between ISO and NSO stock options goes into more detail; the table below covers the essentials.
How Do Stock Options Work? The Lifecycle of Equity
An employee stock option goes through three main stages. Knowing each one tells you how and when your equity gains value.
1. The Grant and the Strike Price
It starts on the grant date, when the company’s board formally awards you the options. Each option is given a strike price: the fixed price you will pay to buy one share. Under Section 409A and the ISO rules, the strike price must be at least the fair market value of the company’s common stock on that date. Private companies support that value with a 409A valuation; using an independent appraiser gives the company a presumption that the value is reasonable, which protects you from the penalties described below.
2. Vesting Schedules and Cliffs
You do not own your options outright on day one; you earn them over time. The common startup schedule is four years with a one-year cliff.
Worked example: a 10,000-option grant
| Period | Options vesting | Total vested | Notes |
|---|---|---|---|
| Months 1 to 11 | 0 | 0 | Nothing vests before the cliff |
| Month 12 (cliff) | 2,500 | 2,500 | 25% vests at once |
| Months 13 to 24 | About 208 a month | 5,000 | Monthly vesting of the remaining 7,500 over 36 months |
| Months 25 to 36 | About 208 a month | 7,500 | |
| Months 37 to 48 | About 208 a month | 10,000 | Fully vested |
If you leave before the one-year cliff, nothing has vested and you usually walk away with no options. Options typically expire 10 years after grant even if you stay.
3. Exercising Your Options
Exercising means buying vested shares at your strike price. If your strike price is $2 and you exercise 1,000 vested options, you pay the company $2,000 and become a shareholder. If the shares are worth more than $2 at the time, the difference (the spread) may be taxable, as shown below.
Worked example: exercising 5,000 options (strike $2, current fair market value $6)
| Item | Amount |
|---|---|
| Vested options exercised | 5,000 |
| Strike price paid ($2 × 5,000) | $10,000 |
| Fair market value at exercise ($6 × 5,000) | $30,000 |
| Spread | $20,000 |
| If NSOs | $20,000 of ordinary income on your W-2, taxed at your income tax rate plus payroll tax |
| If ISOs | No regular income tax now; the $20,000 is added for the alternative minimum tax calculation |
How Stock Options Are Taxed
| Stage | ISOs | NSOs |
|---|---|---|
| When you are granted options | No tax | No tax |
| When options vest | No tax (if granted at or above fair market value) | No tax (if granted at or above fair market value) |
| When you exercise | No regular income tax; the spread counts for alternative minimum tax (AMT) | Ordinary income on the spread (fair market value less strike), shown on your W-2 with withholding |
| When you sell the shares | Long-term capital gain on the whole gain if you hold 2 years from grant and 1 year from exercise; otherwise part is ordinary income | Capital gain or loss on the change in value after exercise |
| Who can receive them | Employees only | Employees, advisors, contractors and directors |
| Leaving the company | Must exercise within 3 months to keep ISO status; later exercises are treated as NSOs | Exercise window set by the plan, often 90 days |
Protecting Employees from 409A Penalties
Many employees do not realize the tax risk they carry if a company gets its valuation wrong. If a company grants options below fair market value, it is generally the employee who pays.
Section 409A of the Internal Revenue Code treats a discounted option as deferred compensation. If the IRS finds options were granted below fair market value, the employee is generally taxed on the spread of vested options as ordinary income as they vest, rather than at exercise, plus a 20% additional federal tax and interest. California adds its own 5% tax. A discounted option also cannot qualify as an ISO.
Worked example: your options have a $2 strike, but the company’s common stock was really worth $3 when they were granted. By year end, 5,000 options have vested and the shares are worth $6. You could owe ordinary income tax on the $20,000 spread that year, plus a $4,000 additional tax (20%) and interest, even though you have not exercised or sold anything.
A Simple Compliance Checklist for Founders
| Step | Why it matters |
|---|---|
| Get an independent 409A valuation before the first grant | An appraisal by a qualified independent appraiser gives the company a presumption that the value is reasonable |
| Refresh at least every 12 months | A valuation more than 12 months old no longer supports the strike price |
| Update after any material event | A priced funding round, a large customer win, an acquisition offer or a big change in results can make the old value stale even within 12 months |
| Set every strike price at or above the current 409A value | An option priced below fair market value at grant is a discounted option under Section 409A |
| Use a qualified appraiser, not a self-serve calculator | The presumption of reasonableness depends on the appraiser's qualifications and a documented method; a bare software output may not support it |
| Keep board approval and records | Board minutes should approve each grant and the 409A value it relies on |
Don't Put Your Employees' Financial Futures at Risk with an Outdated Valuation
Schedule a free 409A consultation with our CPA-led valuation team.
Frequently Asked Questions
1. What is an employee stock option?
An employee stock option is equity compensation that gives you the right, but not the obligation, to buy a set number of company shares at a fixed strike price once the options vest. If the company’s value rises above the strike price, the difference is your potential gain.
2. How does a 409A valuation affect my stock options?
A 409A valuation sets the fair market value of the company’s common stock. Your strike price should be at or above that value on the grant date. If it is lower, the options are discounted under Section 409A, which can lead to immediate tax and a 20% additional tax for you.
3. What happens if a company violates 409A rules?
If options are granted below fair market value, the employee, not the company, generally bears the tax: the spread on vested options is taxed as ordinary income as they vest, plus a 20% additional federal tax and interest. California adds its own 5% tax. Discounted options also cannot qualify as ISOs.
4. What is the difference between ISOs and NSOs?
ISOs (incentive stock options) are for employees only. There is no regular income tax at exercise, though the spread can trigger AMT, and if you hold the shares 2 years from grant and 1 year from exercise the whole gain is long-term capital gain. NSOs (non-qualified stock options) are taxed as ordinary income on the spread when you exercise.
5. How long do I have to exercise my options if I leave the company?
Most plans give 90 days after you leave to exercise vested options. Some startups offer longer windows. For ISOs, exercising more than three months after leaving means the options are taxed as NSOs. Unvested options are usually forfeited when you leave.
6. What is a vesting cliff?
A vesting cliff is a waiting period before any of your options vest. A typical cliff is one year: nothing vests for the first 12 months, then 25% of the grant vests at once and the rest vests monthly or quarterly.
7. How can founders protect employees from 409A penalties?
Get an independent 409A valuation before the first grant, refresh it at least every 12 months and after any material event such as a funding round, and set every strike price at or above the current value. An independent appraisal gives a presumption of reasonableness, which the IRS can only overturn by showing the value was grossly unreasonable.
8. Should I exercise early and file an 83(b) election?
If your plan allows early exercise of unvested options, exercising when the strike price equals fair market value and filing an 83(b) election within 30 days means no tax at exercise and starts the capital gains holding period. The risk is paying for shares that may later be worth little, so weigh it carefully.
Related Countsure Blogs
- ISO vs NSO Guide for Startup Employees: the two option types in detail.
- Master Startup Equity Guide: cap tables, option pools and dilution.
- 409A Valuation Guide: how the strike price value is set.
- 409A Safe Harbor Guide: what protects the valuation.
Parth Shah, Managing Director
(CPA-US, FCA, RV-S&FA, DISA)
Parth Shah who is head of Accounts and Book keeping has experience of more than 10 years. A Certified Public Accountant – US, fellow Chartered Accountant, Registered Valuer and Diploma in Information System Audit.
