User creates an invoice in Core and sends it to Xero with time entry details. In Xero, the user voids that invoice and then tries to resend the original invoice from Core, but without any time details (Integration > Xero > Sync Settings > Invoices > Do not send Time Details). Core gives an error message:
Cannot send invoice that already exists.
This happens because Xero does not allow editing an invoice after it is voided or deleted. Also, it saves the deleted and voided invoices in the All Sales list for audit purposes. So the underlying invoice record exists in Xero even after voiding it.
To fix this issue:
- In Core, go to Integration > Xero > Record Mappings.
Under the Mapped Records tab, select Invoices and unlink the voided invoice.
Then open the Invoices screen and change the invoice number of that invoice you are trying to resend to Xero.
Retry syncing the invoice to Xero. It should sync now without any problem.