Yes, I second this wholeheartedly, for a different reason: if our clients request a refund on a paid invoice or want to cancel an order but maintain the payment as credit, we need the invoice to actually, officially notate this, so that the client will see it if they log in and view the invoice. In this way, we can prevent a client from trying to claim that we didn't refund/credit them properly.
Yes, I second this wholeheartedly, for a different reason: if our clients request a refund on a paid invoice or want to cancel an order but maintain the payment as credit, we need the invoice to actually, officially notate this, so that the client will see it if they log in and view the invoice. In this way, we can prevent a client from trying to claim that we didn't refund/credit them properly.