A co-insurance clause makes you responsible for a proportion of any loss. For example, a 25% co-insurance clause would mean that you are responsible for a quarter of any loss with the insurer covering the remaining 75%. On self-drive hire insurance policies, a co-insurance clause is often applied to ‘theft by hirer’ and, in the case of motorhomes, campervans and certain horseboxes, fire damage claims caused by cooking or heating appliances.