What is it:
A grant notice is part of your award agreement. It is the short summary, usually a single page, at the front of an award agreement that lists the details of your specific grant. Grant notices are most common with option grants, though RSU and PSU agreements can open with one as well. The grant notice is usually the page you sign or accept electronically, and accepting it means agreeing to the full award agreement and the company's plan document. For a stock option, the grant notice typically lists the grant date, the number of shares, the strike price, the vesting commencement date, the vesting schedule, the option expiration date, and whether the options are incentive stock options (ISOs), non-qualified stock options (NQSOs), or a mix of both.
Why does it matter:
Everything else in an award agreement is standard language the company uses for grants like yours. The grant notice is the one page written specifically about you. That makes it the place to check your grant against everything you were told about it, whether in a conversation, an email, an award letter, or an offer letter. Written communications deserve the closest comparison: the share count, the option type, and the date your vesting starts should all match.
What do people most often get wrong:
People often assume their vesting clock starts on the grant date. Many companies set a separate vesting commencement date, such as a new hire's start date, because the board or compensation committee may not formally approve a grant until weeks after it was promised. Grant notices usually label this date the vesting commencement date or vesting start date, but companies don't use those labels consistently. The vesting schedule itself is the reliable guide.