The purpose of this article is to explain the cause and resolution when you come across the error ‘Cannot Duplicate Invoice Numbers for Supplier While Using Xero Integration (Xero Will Not Allow This)‘
We have had to restrict the system for Xero users to align our system with Xero. Invoices for the most part sync to Xero instantaneously. The issue is if you void that invoice in Workshop Software it then updates the status in Xero as voided. So, you are left with a voided invoice in Xero.
Even though the invoice is voided, the supplier invoice number had been used. Xero will not allow you to use that invoice number again. We have had to put this restriction into your system because if you create another invoice with that same supplier invoice number it is not able to sync to Xero as Xero will not accept it again. You would end up getting the error if duplicates were allowed..
"Invoice not of valid status for modification"
To get around this, you need to alter the supplier invoice slightly so that the invoice number is different but similar enough that you know that what invoice it relates to. We suggest putting an extra character on the end of the invoice. eg, instead of 123456 you out 123456-b.