Does J!Invoices automatically create customer Account Numbers? If not how hard would it be to create a new field so that I could manually add account numbers, that would appear on both on the front-end and back-end as well as invoices with the customers account number.

So basically just like a persons contact info appear on the admin and customer side as well as the invoice, can I have their account number implement as well. Preferably between the date and invoice number on the invoices?

Would this be the same method as mentioned before about adding telephone numbers?