Car hire companies in the UK, like every other car owner in the United Kingdom are required by law to have insurance for the vehicle covering third party risk. This mean that the vehicle has to have insurance cover for the eventuality that the vehicle is involved in an incident in which third party property is damaged or a person is injured.
So when you rent a car from a car rental company in the UK this insurance cover will be in place without you having to pay for it directly as part of your rental cost. The car is likely to have comprehensive insurance included in the rental cost. This covers the cost of repair to the vehicle in the event that it has been damaged.
However, due to the insurance costs incurred by the car hire company, they normally try to offset their costs by having an insurance excess or deductible on their policy. The excess amount could be in the region of GBP 600.00 and could be more if the vehicle is a premium type car, like a sports car.
The car rental company make the person hiring the car responsible for the insurance excess amount.
This means that in the event that the car is damage, the renter would be responsible for the first GBP 600.00 of damage to the car, if the excess has been set as GBP 600.00. By doing this they reduce their insurance costs and also give the renter an incentive to try and avoid the vehicle being damaged.
When a vehicle is returned damaged to a car rental location, the car rental staff will normally work off a chart of sorts to establish the approximate cost of repair. They will then apply this cost to the hirers credit card. In the event that the cost of repair is actually less than the amount charged to the credit card, there is some doubt that the car rental company actually contacts the hirer to refund the difference. The hirer should make a point of contacting the car rental company to establish what the exact of cost of damage was in case they are entitled to a refund.