The following topics should be automatically setup in the Prepayment Invoice of the Sales Orders:

1. Customer Posting Profile which is setup in the accounts Receivable Parameter (Ledger and Sales Tax - Posting profile with prepayment journals) - automatically put in the header of the prepayment invoice
2. Item sales tax group from the sales category -automatically put in the lines of the prepayment invoice
3. sales tax group from the customer account --automatically put in the header of the prepayment invoice