You can add as many fees onto the one invoice as you wish. However, for invoices to be processed by Medicare, you can only submit a maximum of 13 fees on the one invoice.
To add multiple fees onto an invoice:
From the invoice, click Add Another Fee in the Fees & Charges section. The "Add invoice line" pop-up appears.
Type or select the fee from the drop-down menu and click Save.
Repeat the process for each fee you would like to add.