Hi, it would totally depend on the nursery. The problem is most nurseries have a settling in process for children coming on regular days. And I can't see how you could just leave a child without having done that. I have occasionally seen crèches where they are literally turn up and pay as you go- quite rare though.
You normally have to pay up front at the beginning of the month Otherwise you could book a place and not turn up and not pay but the staff would still need paying The nursery would soon go out of business