You provide an employee with food, groceries, farm produce or other edible produce with no resale value.
For employees earning at a rate of less than £8,500 per year, you have
For company directors or employees earning at a rate of £8,500 or more per year:
The value to use is the cost to you of providing the food or groceries to your employee.
To check what's included in the £8,500 threshold for P11D reporting purposes, follow the link below.