Accounts and their tickets can appear to be duplicated in the pre-invoicing report if the accounts primary address details have been changed.
The pre-invoicing report looks at all tickets against an account that have not yet been invoiced. If the address details for that account have been altered between transactions being generated then the system will see multiple address details against the same account number, and the only way it can reconcile that is to display the tickets separately for each set of address details it sees.
Example
You create 5 transaction against account A001 on Monday which has the primary address of "12 The Street".
On Tuesday the accounts primary address is changed to "13 The Street". On Wednesday you create 5 more tickets, which will now display the account address of "13 The Street".
If you then go to the pre-invoicing report you will see 2 entries for account A001, each with 10 tickets against them. One set will show "12 The Street" and the other will display "13 The Street".
Note: This issue is purely display-related and if you do the invoice run the system will not produce multiple invoices for the same tickets. If you require the tickets to all show the same address details please raise a case with support and it can be looked at.