Clients have the right to know what happens with their money. What they owe is clearly displayed and managed with invoices. That is for good us, because they might help the client to pay what they owe us and we earn our money.
However what we owe them is not so clear. In the client area there is not even a Credit Balance indicator. With every upgrade I need to re-implement my own solution in a template, which costs lots of time updated new templates. Please save me time and provide this for our clients in all your templates. Better would be when there is a Credit History for clients, just like they have invoice history.