To begin, set up an appointment for a patient and go to complete it after the treatment has finished. You should be met with this quick bill screen:
Select 'Pay Later' on the quick bill. This will generate a charge for the patient against the group, in this case it's Bupa.
That charge will reside on the groups financial account as uninvoiced here:
You can change how invoicing is processed on the groups account under their group settings here:
Select the invoicing method that is most appropriate to you. Then when you want to invoice all of your charges simply navigate to the finances tab and select 'Invoice wizard'. Select the group that you want to generate invoices for and it should show all charges related. Simply select the charges then press 'Generate invoices'. As shown below:
Once you've done that you can send the invoices to the relevant group using the communications options on the invoice or send them externally.