Invoice ID

You guys have an ID for everything but invoices and it makes it really hard trying to explain billing on a ledger that is continually running. Its easy for me to understand and work with but always seems to be an issue explaining it to parents i think they would prefer if an option was available for Invoices with an invoice id so its easier to track or some sort of option in which we can track families invoices by number not just a charge, Please and Thank you