611 reliability for X12 specifications

:

Just had a call with an 835 contract vendor

and the debate was on 835 TRN 03 field – Originating Company ID (also being called Taxid)

The ASCx12 document says it is REQUIRED

The cloverleaf format says: Optional

So the above begs the question – it appears…..that I  cannot rely …to some degree on the definition of the X12 versions that we purchased as part of the Cloverleaf Package?   Specifically 5010A1