You can view the list of clients with invoice raised, payment received and pending payment in the overall page along with any kind of future followups required.
You can add future followup update by never missing any kind of future communication with your client. Simply add with the narration as well, so that it will help you to remember the things needs to be done in an effective way.
In the view page of clients, you can be able to view the list of invoice & proforma invoice created along with the details of the complete history.
Apart from the generic data, you can upload multiple files related with the client in the view page of the client.