Stocks and shares: Share Option Schemes: what is a Share Option Scheme?
These are schemes by which an employee has a right to purchase shares at a fixed price. In the event of death/transfer within the option period, the employee or their legal personal representatives (IHTM05012) may have the right to exercise the option within say, the next 12 months. If so, the option is a chargeable asset of the estate.
You can find more information on the types of schemes and how to deal with them at IHTM10351.