Hello, 

I would like to provide input as when an invoice is in the draft stage and the customer previews it, it appears as a "PROFORMA" draft invoice. Upon confirmation, it is displayed as a "PROFORMA" invoice. 

Once the invoice is sent to the customer through the “Send and Print” button, it is labeled simply as an "Invoice". Hence. if you print the invoice from preview until it is sent to the customer it will be printed as a Proforma draft invoice/ Proforma invoice. Once the invoice is sent to the customer, it will be printed as an invoice. This behavior has been improved from version 17 and it is designed to reflect the invoice status accurately: during the draft and confirmed stages, it is considered provisional until the customer approves it. 

Once you send it to the customer, then it is identified as a consolidated invoice. So, "proforma" is just a temporary label until it's officially sent out. 

The video representation taken on a runbot is attached below, Standard runbot version 17: Video

I hope you will find this information helpful. 

Have a nice day!