When importing sales invoices from clients system, if an invoice number is duplicated the system just renumbers, this is not useful, it needs a flag to say there are duplicates, or a report at the end to say the following have been renumbered by the system, then we can investigate and correct, otherwise when the next import is done it just snowballs as we will be importing invoice numbers the system has already created and so it goes on.
This is not helpful, why cannot the system just fail the import with the message duplicate entry.
The system obviously recognises the duplicate as it re-numbers, it cannot be that mush work to change the outcome to fail import