Each rental supplier has their own way of collecting payment - some do take full payment upon booking as a matter of course, while others take a deposit and charge the balance upon picking up the vehicle. Others operate on a ‘pay on arrival’ basis, meaning you will pay the full amount at the rental counter. The payment type will be outlined on the booking page. If you book a car that is to be paid on pickup, you can contact the supplier after you have paid the deposit and received a confirmation to ask them whether they will accept an early payment.