Include Previous Balance or Past Due Amount within invoice

Invoice should show total current charges AND would be nice to display past due amount within the invoice they open each time. Separate from the "Generated Statement." Sometimes a client misses an invoice and thinks they are caught up, they often don't bother to open separate statements, only the "PAY BILL" link. A Past Due amount would be a valid indicator of money still owed. When they are missed and I call from an AR stand point after time has passed, they don't always trust that they haven't paid (not to mention wasted time on both ends to validate). Displaying if they have a previous balance, or past due amounts with EACH invoice would be an efficient way for all parties to help verify and stay up to date. If you can't create the logic for repeat customers, then for one time invoices that could display as N/A.