How to set it up?
Simply go to Settings - System - Online settings and tick:

Payment is only possible with credit of the Bonus type (Barter, Members and Employee types are not supported).How does it work?
In OBE, the guest then has the following option when paying for the reservation:

In the reservation, a payment is then inserted:

If the amount due is 0 when the guest checks out, clicking Check-out will not redirect to settlement, but will immediately close the reservation account