In accounts payable module parameters, the "Check the invoice number used" field is set to value "Warn in case of duplicates". However, an invoice was posted in December 2020 using a supplier invoice journal and it was possible for a duplicate invoice to be posted in January 2021. The user did not receive any warning message when the user clicked on validate in the journal.

When the user tried to post the same invoice again in February 2021 and clicked on validate the user received the duplicate invoice warning message. It looks like this this parameter only checks for duplicate invoices if they are posted in the same financial year.

There are lots of companies that do not refresh their invoice number sequence. The difference between “Reject duplicate” and “Reject duplicates within accounting year”? Surely “Reject duplicates” option will reject duplicate invoices no matter which fiscal year and “Reject duplicates within accounting year” will be the option that rejects duplicates within financial year and will ignore if the same invoice number exists in previous year. Therefore, we should ideally, have a Warn in case of duplicates within accounting year option too.