Online payments for appointment bookings provide the capability for practices to set a deposit (in the Booking Reason setup) for each of the booking reasons.
Note that if your practice has configured online booking payments the Booking Reason window will include a Deposit field where you can specify a deposit amount (less than the Price) to be paid online:
It also creates a payment method of .OLB (Online Booking), for use when EXACT receives a payment through online booking. The .OLB payment method is not available for use with standard (offline) payments.