Once signed and dated, the document is legally binding. Just because the details are in the schedule and not in the main document does not mean that they can be changed without the agreement of all parties. A stock option is the right to buy a certain number of shares at a fixed price, a certain period in the future, within a company. This document is signed in accordance with fundamental contract law. There are no specific rules, tax rules or other legal complications that need to be taken into account in such an agreement. .