How do startup stock options work? They give you the right to buy shares at a preset price once they vest, typically over four years with a one-year cliff. Exercising is a purchase, not a gift.
This walkthrough follows one grant from offer to exercise to a possible shutdown. It is part of our wider guide to working at a startup as a software engineer.
What an option grant gives you
A stock option is a contract that gives the holder the right to buy a specific number of shares at a pre-set price, as Pasquesi Partners describes it. On the day you receive the grant you own no stock. You hold a right that becomes usable in stages, and only a purchase turns it into shares.
Your options come from the company’s employee option pool. Capbase describes a pool as consisting of 10% to 20% of company ownership. That range tells you the pool is shared among many hires, so the number in your offer letter only means something next to the company’s total share count. A large grant of options in a company with a huge share count can be a small stake.
Four terms define your grant, and each is covered below:
- Strike price: what you pay per share when you exercise.
- Vesting schedule: when you earn the right to buy.
- Exercise window: how long you have to buy after you leave.
- Option type: the tax category of the grant, set out in your agreement.
Strike price and the 409A valuation
The strike price is fixed when the option is granted, and it comes from a company valuation rather than a negotiation. That valuation is the 409A valuation, so it is the first number to understand.
What a 409A valuation is
A 409A valuation is the independently valued fair market price of the company’s shares, according to Justworks. Because an outside party sets it, the company cannot simply pick a convenient figure. Capbase says the strike price is typically a percentage of that valuation, and Justworks notes the exercise price is normally lower than the 409A fair market value.
In practice, ask which 409A valuation your strike price is based on and when it was done. A strike price built on an older valuation can differ from one set after the company has grown.
A worked example of a strike price
Capbase gives a simple case. A company is valued at $2M with 4M shares, so each share is worth 50 cents. When the company issues options, the strike price is also fifty cents.
That is the number you would pay per share at exercise, however much the company is worth later. If the shares become worth more than fifty cents, buying at the strike captures the difference. If they never do, you have no reason to exercise. The example is deliberately simple, because real strike prices are usually set as a percentage of the valuation.
Vesting schedule and the cliff
A vesting schedule is the timetable on which you earn the right to buy your options. The common startup pattern is a four-year vesting period with a one-year cliff, according to Justworks. The cliff is the first milestone: nothing vests until you reach it, and then a large block vests at once.
| Stage | What vests | Planning use |
|---|---|---|
| Before the one-year cliff | Nothing | Leaving early means walking away with no options. |
| At the one-year cliff | 25% of the grant | The first point at which you hold any right to buy. |
| Each month through year four | 1/48th of the grant | Each further month of service adds a small, steady amount. |
These terms come from Justworks and Crunchbase.
The cliff matters most to people who might leave within the first year. Crunchbase puts it bluntly: an employee who leaves on day 364 gets nothing. If you are weighing a role you are unsure about, put the cliff date in your calendar and treat it as the point where the grant starts to have value.
Vesting does not make you a shareholder. Once options are vested, you still don’t own the actual shares, as Pasquesi Partners explains. You own the right to buy them, and the purchase is a separate step.
ISO vs NSO: the tax type of your grant
Options come in two tax categories, incentive stock options (ISOs) and non-qualified stock options (NSOs). Your grant agreement states which one you hold. The difference changes how an exercise is taxed, so it affects how much cash you may need beyond the strike price.
The practical advice is to read the type in your agreement before you accept, and to take any exercise decision to a tax professional first. Pasquesi Partners treats tax as a core consideration whenever you exercise startup stock options. Do not assume the paperwork will answer the tax question for you.
Exercising your options and the exercise window
Exercising means buying your vested shares at the strike price. Pasquesi Partners puts it plainly: the act of buying vested shares is called exercising. You pay the strike price for each share you choose to buy, and the shares become yours.
The exercise window is the deadline for doing this after you leave. Most companies require employees to exercise within 90 days of leaving their positions, per the same source. Treat 90 days as a typical deadline rather than a guarantee, and check the number in your own agreement, because it controls your choice.
Leaving a job therefore forces a decision on a short clock:
- Find your vested total. Only vested options can be bought, and unvested ones do not carry over.
- Price the purchase. Multiply nothing in your head; ask the company for the strike price and the latest valuation in writing so you can compare them.
- Get tax advice. Do this before you pay, not after.
- Decide before the deadline. If the window closes, the right to buy lapses.
What happens if you leave or the startup fails
What happens depends on whether you are leaving or the company is closing, and on what has vested. If you leave, unvested options are forfeited back to the option pool, according to Crunchbase. Anything already vested stays available to buy, but only until the exercise window closes.
If the company fails, the position is harsher. Once a company shuts down or goes out of business, your equity does not have any value, as Justworks puts it. Options you never exercised lapse worthless, and shares you did buy are worth nothing either.
That is the real risk in the exercise decision. Exercising spends your own cash on shares in a company that might fail, so it suits you best when you have a reason to believe in the company and can afford to lose what you pay. If you are unsure, you can let the options expire without owing anything further.
Questions to settle before you accept
An option grant is only as good as its terms, so get them in writing. The offer letter and grant documents should answer these:
- Strike price and valuation date: which 409A valuation it comes from.
- Vesting start and cliff: whether it follows the common four-year pattern with a one-year cliff.
- Exercise window: whether it is the typical 90 days or something different.
- Option type: ISO or NSO.
- Total shares outstanding: so the size of your grant has meaning.
These terms sit beside cash pay, so compare them with the early stage startup developer salary you are being offered. They are also the points you can raise when you learn how to negotiate startup job offer engineer packages, since equity terms are part of the conversation.
Frequently asked questions
Do I own company shares once my options vest?
No. Vesting only gives you the right to buy shares at the strike price. You own stock after you exercise and pay for it.
Is a four-year vest with a one-year cliff always the rule?
It is the common startup pattern, not a law. Your agreement sets the real terms, so read the vesting section rather than relying on the usual pattern.
Is my strike price the same as the 409A valuation?
Not necessarily. The strike price is typically a percentage of the 409A valuation, and the exercise price is normally lower than the 409A fair market value.
Can I lose money on options if the company closes?
Unexercised options simply become worthless. Money is lost if you already paid to exercise, because equity has no value once a company shuts down.
