A sales invoice is a bill that an organization gives to a customer in connection with a sale. You create a sales invoice based on a sales order, which includes order lines and item numbers. Item numbers are specified and posted in the ledger.
A free text invoice is not related to a sales order. It contains order lines that include ledger accounts, free-text descriptions, and a sales amount that you enter yourself. You cannot enter an item number on this kind of invoice. You must enter the appropriate sales tax information. A ledger account for the sale is indicated on each invoice line, and the customer balance is posted for each customer group, unless specified otherwise. A free text invoice cannot be partially posted.
A pro forma invoice is an invoice that is prepared as an estimate of the actual invoice amounts before the invoice is posted. You can print a pro forma invoice for either a sales invoice or a free text invoice.