It is possible to allow interim payments on a booking-by-booking basis. This allows guests, e.g. larger parties, to pay in several instalments instead of having to pay the deposit and then the balance only.
Otherwise the guest will only be able to pay the amount due at any one point.

To enable the guest to pay custom (guest chosen) amounts do the following:

1. Go into the booking.
2. Tick the box to the right of Custom payment enabled.

3. Click either of the Save buttons.

On the payment page there is now the option for the guest to either pay the amount due or an amount of their choosing.