The template refers to template of
Unpaid invoice (Invoice generated for a sales transaction)
Paid invoice (Receipt sent after a successful purchase, renewal or top up)
Monthly tax invoice (Monthly statement of usage, purchase and credit balance)
Postpaid monthly tax invoice
You can configure your invoice templates at Portal settings app. Instruction can be found at https://b3networks.freshdesk.com/support/solutions/articles/28000004868-invoice-settings