Hi there, 

I am using Odoo 12  Community Edition for a client who had already started his business 2 years ago. Their invoice sequencing is easy to set up from today on; but I need to include all past invoices both for clients and suppliers as well. 

I started by leaving empty both invoice sequences in the developer options, which enables me to type in a custom id for a start. Now I need to use different characters in order to get an ID like this: FC %(year)s-%(month)s%(day)s/.

My problem is that while creating new items, I'm unable to include letters or any other character that isn't a number in the invoice ID field. 

I know I can edit the sequence so it has the FC prefix but what about including other characters in between the numbers? I could edit the sequence so it has the FC prefix but what about including other characters in between the numbers?  

For example, say I want to create an invoice with ID: "FC 2018-0701/1"; Odoo won't use the bold and underlined characters, making the invoice number be: 201807011.

Does anyone know a way around this issue??

Thanks in advance!