A compulsory excess is a deductible or the amount of loss you have to bear before your insurer pays the balance of your claim. This amount is usually set by your insurance company and it is non-negotiable. You may have to pay a compulsory excess if, at the time of accident, your vehicle is driven by a person who is not named in your policy, under the age of 21, a provisional (L) driving license holder or the holder of a full driving license of less than two years.