Sales Invoice is a document made by a seller to specifying the details about the products/services ordered by a customer after they confirmed their orders. So it's a document for a Customer after they willing to confirm their transactions.
When you have customer who has not paid, and you want to set Bill Label for Unpaid Invoice. You can change the default bill label on Printing Configuration.
Invoice bill will automatically updated after you change bill label.
Follow the steps below to Change Bill Label for Unpaid Invoice :
Step 1. Go To Setup
Step 2. Select More Menu and Choose Printing (Configuration)
Step 3. Set Your Own Bill Label, Then Click Save
Step 4. Try to Check Your Bill Label on Customer Invoice
You might also like to read these articles below :
To print more than one invoice, you can read this article Bulk Print Invoice
To configure customer invoices, you can read this article Customer Invoice Printing Configuration
To search product and invoice note in orders read this article Search Orders by Product & Invoice Note