If you're an opted out practitioner such as an Optometrist or Allied Health professional,  you will need to set up your invoices a little differently. Under the Advanced tab, the invoice type will need to be changed to "pay patient"

You can use a 'default invoice' to automatically make any new invoice you create defaults to these details. To do so you need to navigate to 'preferences' from the left side menu, and 'default invoices'. Create a new form, and click 'set as primary'. Edit the form per the above screenshot with the Insurer type adjusted and save

Lastly, as an opted out practitioner, you will need to transmit the payment with complete patient demographic information including the patient's first/last name, PHN, date of birth, Gender, and address information. These details can be added to the patient tab when creating an invoice, or if they are already added to the patient record, all of the information will automatically be added to the invoice when it's created.