Hi Guust. I did consider this however all the fields are in use so unfortunately I can’t use this option.
Hi Patrik. So far I have only been asked me to quote their reference number when sending an invoice. I guess they need it for internal accounting purposes; They may perhaps need this in order to get their finance team to make the payment for their listing.
So, at the moment I only need this as something to be edited on the invoice in the backend, however, it might be worth giving it some thought to see whether there would be benefit in having this at checkout.