Suggestion - Autonumbering Custom Field

Auto Reference No is required. it is said many times that Supplier Ref No is OK. we are having problem in archiving the purchase invoice. on what basis we should file the invoices. and it has been raised by our external audit last year when he want to take the sample. he need our ref no to select the purchase invoices between these system ref no.

it almost all the tabs now have a system reference no except Purchase Invoice.

having this feature will help us in archiving the purchase invoice as per our system no Not Supplier No

in case you see this is not important to implement please let us have auto numbering in customs field as per your positive reply in the shared link

your support in this matter highly appreciated.