The Pro Forma invoice is the document that you can issue to ask for advance payment for the confirmation of a booking. In this way, you do not have to issue an invoice and consequently you don’t run the risk of issuing the relative credit note if the booking is not confirmed.
From the list of client invoices click on +.
Enter the requested data and, in the Series field, select Pro_forma.
At the moment of payment, to transform the pro forma invoice to a fiscal invoice, access the invoice, and in the Series field, choose the current series for your invoices and save.