For example you are expected to arrive at the campsite/holiday park on Saturday, but you can only arrive on Sunday. In many cases this is possible, but you will have not be refunded for the Saturday night. We always have to check this for you in advance. Not all suppliers offer this possibility as they may not be available on Sundays.
If the campsite/holiday park is not notified about your late arrival, they have the right to give your accommodation / pitch away.