To delete an invoice, go to the Patient File > Invoices tab > select Invoices.
Select the Invoice, by selecting the tickbox to the left of the invoice number.
The next screen will ask you to confirm by typing Delete and by giving a reason.
If the invoice has a payment allocated against it, select if you would like to either Make Payment Unallocated (a credit) or Delete Payment.
Or if one or more payments are associated with multiple items they can only be Unallocated.
Select Delete to confirm.