A customer can not pay immediately or has no money in his pocket?
You want to be able to keep track of the fact that the customer still has an outstanding bill to pay?
This can be done by activating the "credit" button at the cash register via
3. Payment methods
4. Activate "On tab" (blue frame is around it)
5. Press "Save"
If you are now going to finalize a customer through the cash register, there will be a "credit" button next to the known payment methods (cash, bancontact, pin, ..). With the "credit" button you can then pay off at the moment the customer does not have enough money or will pay later.
When the customer returns for the next visit and receives treatment again, the outstanding amount will automatically be added to the new bill.