Far East Proforma Invoices

Oni

Seeking some advice from the group about proforma invoices, specifically from the Far East.
I work for a company that have a large amount of proforma invoices, a large percentage of these are received from the Far East.
From experience, I know that a proforma invoice is not seen as an official invoice, however I am finding it very difficult to get an 'official invoice' from any of our Far East suppliers - I suspect that this is a cultural thing, as they simply see the proforma invoice as an 'invoice'.
Having spoken to a counterpart in one of our European offices, they process the proforma invoice to the ledgers as official invoices. I appreciate that there are different guidelines and laws to adhere to across the globe, so this (I'm hoping) is acceptable in their country. I am not finding anything really very helpful on the HMRC website to help me with this dilemma.
Just wanted to add this discussion to see how other people cope with this problem and if FE proformas are accepted as official invoices and if so where can I find that in writing!
Any help on this subject, much appreciated.
Thank you.