In addition to recurring payments, billwerk also offers you the possibility to process one-time purchases via the system.
Option 1 - Plan variant with immediate termination:
First create a new plan variant in the Products tab.
Set the setup fee or recurring fee to the amount of the one-time payment and the other fee to 0. Set the contract term as well as notice periods to one day and activate the option: "End after first contract period".
If a customer now orders this plan variant, a one-time payment in the amount of the fee / setup fee is triggered and the contract is automatically terminated the next day without triggering any further payments.
Option 2 - Plan variant as container and booked metered component:
First create a new plan variant in the Products tab by clicking "Add Plan Variant".
Set the fee and setup fee to 0, also select the option "End after first contract period". The plan variant created serves as a container for the one-time payment.
Also create a component of the type "Metered" in the amount of the one-time payment. Instructions can be found here.
In the UI, you can also post one-time purchases for your customer contracts as described here.