Question
Unique identifier for invoices
I am looking to provide a feed to an external system and need unique identifiers for each invoice and debit memo. The transaction number does not work because if I make an invoice today or a debit memo and go back and change it tomorrow (make a comment etc) it will give it a new transaction number. Is it possible to create a field in the template and have it self number and keep that number even when I go back to that invoice or debit memo and make changes? (And not allow duplicates in that field)?