Open the service under Services & Booking, then Services. The Deposit card is headed Deposit and it says require a deposit at time of booking.
No deposit means the customer books without paying now. Use that for a quick appointment you can refill.
Fixed amount is a set sum, such as twenty pounds, whatever the price of the service. Percentage of price takes a share of that service, which suits a colour or a long job where the price varies.
Capture timing is beside the amount. At time of booking takes it when they confirm. On completion takes it when the appointment is finished. At time of booking is the one that protects a gap.
Save the service. The next online booking of that service asks for the deposit before it is confirmed. A deposit already taken stays taken. Changing the rule does not go back and charge old bookings.
Put deposits on the appointments a gap hurts. A fringe trim can live without one. A half-day colour should not.
Common questions
Does the deposit come off the final bill?
Yes. It is part of the price, collected early, not an extra fee.
Can one service take a deposit and another not?
Yes. Each service has its own Deposit card. That is the point of setting it here rather than once for the whole business.
What if they pay the rest on the day?
Take the balance when they arrive, the same way you take any other payment. The deposit is already recorded on the booking.