Is there a way of applying for credit on the invoice not to the invoice so that the amount due is really amount due?

What happened is that customer prepaid and the credit sitting on deferred revenue. When I invoice the customer in a month, see the sales is $100, the same time I would like to show $100 credit already applied to the amount, so the amount due is 0 on the invoice so that the customer see the in and out on one place. 

Thanks