On July 16,2015 WHMCS Company release version 6.0.1 with a new setting named "Store Client Data Snapshot" that has been added in Setup -> General Settings -> Invoices. Enabling this, you can store a copy of the clients data (e.g. name, address, custom field data, etc.) each time an invoice is generated, so that any future changes to the clients profile information do not result in any changes to existing invoices. The problem is that, invoices created before "Store Client Data Snapshot" setted does not have store separate client's data snapshot (if a client change his details, all the invoice details change too). Also you can not change snapshot data stored in the invoice. This Addon comes to solve this problem.