Employee resource center

How do stock options work?

September 9, 2022
Adam Lewis

A stock option is a form of equity compensation that allows an employee to buy a specific number of shares at a pre-set price. Many startups, private companies, and corporations will include them as part of a compensation plan for prospective employees. 

Stock options explained 

Stock options aren’t actual shares of stock—they’re the right to buy a set number of company shares at a fixed price, usually called a grant price, strike price, or exercise price. Because your purchase price stays the same, if the value of the stock goes up, you could make money on the difference. 

Types of employee stock options

There are two types of employee stock options: incentive stock options (ISOs) and non-qualified stock options (NSOs). These mainly differ by how and when they’re taxed—ISOs could qualify for special tax treatment. Companies often offer stock options as part of your compensation package so you can share in the company’s success.

Instead of stock options, some companies offer alternative equity awards, such as restricted stock awards (RSAs) or restricted stock units (RSUs). These types of equity awards are not the same as stock options, and are treated differently for tax purposes. 

Stock option agreement 

When you receive an offer letter from a company, it might mention how many stock options the company is offering. But you’ll still need to receive and sign the stock option agreement (also called an option grant or stock option grant) if you want to purchase your shares someday—simply signing the offer letter isn’t enough.

Stock option grants are how your company awards stock options. This document usually includes details about:

  • The type of stock options you’ll receive (ISOs or NSOs)
  • The number of shares you can purchase
  • Your strike price
  • Your vesting schedule

Your stock option agreement should also specify its expiration date. In general, ISOs expire 10 years from the date you’re granted them. However, your grant can also expire after you leave the company—you may only have a short window of time to exercise your options (buy the shares) after you leave. If you don’t exercise your options before then, you’ll lose the opportunity to purchase them.

Ask your company if you didn’t receive a stock option agreement. If you just joined in the last month or two, it’s possible that the board has not yet approved your options, in which case you should receive the agreement shortly after the next board meeting.

Remember: If you hope to purchase and sell your stock someday, accepting your stock option agreement is the first step you have to take. It doesn’t cost anything to accept the agreement, and you’re not obligated to actually exercise your options. By accepting it, you’re simply giving yourself the opportunity to exercise in the future. 

If your company uses Carta to issue options, you won’t receive a paper version of your stock option agreement. Instead, simply log into your portfolio to view, accept, and print the actual agreement.

How do stock options vest?

Vesting is the process of earning something over time. Companies use vesting to encourage you to stay with them and contribute to the company’s success over many years. 

Vesting schedules

Vesting typically occurs on a time-based schedule outlined in the stock option agreement. The vesting start date should be listed on your option agreement. Many companies have a vesting schedule that is four years long, often beginning with a standard one-year “cliff.”  A cliff is a period of time that has to elapse before you get any of your vested options. 

stock options vesting schedule with 1 year cliff

For example, Meetly is a company that offers options on a four-year vesting schedule with a one year cliff. At Meetly, the vesting start date is the employee’s first day of work. If you take a job at Meetly that includes an award of 100 stock options, you’ll start the vesting clock on your first day of work—but you won’t get your first tranche of 25 options until your one-year work anniversary. After that, you’ll have the option to buy 25 shares. The rest of your options will continue vesting monthly according to the vesting schedule.

Without the cliff, you could accept the offer, work at Meetly for a month, buy a bunch of the company’s stock, and then quit. An option grant that includes a cliff prevents that.

How do stock options work after termination?

If you leave the company, your options will most likely stop vesting immediately, and you may only have the right to purchase those options that have vested as of the date you leave the company. You only maintain your option rights for a set window of time after termination, called a post-termination exercise period (PTEP). Historically, many companies used a standard PTEP of  three months or 90 days. However, some companies offer more generous PTEPs now. At Carta, for example, you have as long as you worked at the company to buy your shares.

Don’t forget about this window of eligibility. Your company isn’t obligated to remind you when you leave — they usually only tell you in your option agreement when you first join.

Knowing what stock options are and how they work can help you make more informed decisions about when to sign your option agreement, when to exercise your options, and what to do when you leave your company. 

Carta Tax Advisory helps employees understand the tax implications related to their equity compensation. Founders who use Carta can take advantage of this service for their employees. 


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This article was originally published on November 15, 2019.

DISCLOSURE: This communication is on behalf of eShares Inc., d/b/a Carta Inc. (“Carta”).  This communication is for informational purposes only, and contains general information only.  Carta is not, by means of this communication, rendering accounting, business, financial, investment, legal, tax, or other professional advice or services.  This publication is not a substitute for such professional advice or services nor should it be used as a basis for any decision or action that may affect your business or interests.  Before making any decision or taking any action that may affect your business or interests, you should consult a qualified professional advisor.  This communication is not intended as a recommendation, offer or solicitation for the purchase or sale of any security. Carta does not assume any liability for reliance on the information provided herein. 

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