Standards & EDI
Companion Guide
Draft — pending verification
This reference entry has not yet been verified against its authoritative source (Original definitions; regulatory facts to be verified against CMS-0057-F (89 FR 8758) and X12/HL7 documentation). Do not rely on it for production configuration until this notice is removed.
In more depth
Companion guides cannot legally contradict the base implementation guide, but they narrow choices the standard leaves open. Reading the target payer's guide before building — especially around member ID formats, UMO identifiers, and attachment handling — prevents most onboarding rework.