I use this 7 digits numbering format for invoices:
year + month + auto increment number
according to the other threads, new invoices use number equals to the highest invoice number + 1. If I manually create an invoice with number 1905001 at the beginning of May 2019, the next invoice would be 1905002 automatically. This has been working fine until…
One day a customer disputed an invoice 1904003. It was indeed my colleagues’ fault so we decided to give the customer a discount on some of the invoiced items. Since the invoice has already been sent, I suffixed the invoice with R (for revision) to avoid mixing up with different versions of the same invoice. The dispute carried on and we eventually settled with 1904003r4 (4th revision). This causes a problem. The revised invoice now has an extra digit and become the biggest number. automatic numbering for new invoices now starts with 19040035 (8 digits).
Since the invoice has already been sent to the customer by email, editing the invoice number would cause inconsistency, eg in future statements. How should I resolve this?