Refund by "customer account payment" is not supported by channel return policy: As "customer account payment" is not a typical tender type that will generate corresponding payment transaction. Instead, it deducts customer's account balance and customer need to pay it back later using other concrete payment (like cash, check or credit card). While Commerce "channel return policy" feature depends on the payment transaction to calculate refund options. Since there is no payment transaction for customer account payment, there is no refund option for this scenario.

But there is a business need where customers can place an order using customer credit amount and provide the possibility to return the order prior the net days of payment and do the return by customer account.