Does Prepayment functionality require Receipt method assignment at the customer account?

Hello

We are looking to utilize Oracle standard prepayment functionality on sales orders, and we noticed that when we enter two lines for the prepayment on the payment form (actions - Payment), one for the invoice another for the prepayment receipt, then our order is not being invoiced unless we assign the receipt payment method associated with the prepayment type at the customer account level. Autoinvoice program completes with the error :

Errors:  1) The supplied payment method must be defined and active for the bill-to customer or site. (ACH Bank Transfer)

However, if we enter only one line for the prepayment receipt, then the requirement for the receipt payment method is not applicable, and autoinvoice creates an invoice from a prepaid order.