In Custermers drop down we need to be able to select Custermers by accepted and unpaid Invoices or is there a upgrad with this built-in ?

Hello Grahamparamountr, thanks for posting on the Community page, if you click on sales> customers>click on a customer>transactions list> status (change the status to what you want to see for example overdue)  you can also have a look in the reports section and for example look at the report open invoices for example.