Multiple mappings are unavoidable.  A payer cannot always know with certainty given a particular SNOMED code what billing code will result or what modifiers might come into play.  This specification cannot dictate who is to perform the mappings.  The mappings will likely change and evolve based on real-time experience.  As payers see how particular SNOMED codes typically show up in claims, the mappings can be adjusted to reflect that reality.  As such, even if the original mappings are sourced from other organizations, they will eventually be maintained by the payer. If there are specific mappings available (particularly free mappings), we can certainly call the payer's attention to these.   Will add the following language: "It is more efficient if mappings can be shared across payers and providers.  This implementation guide encourages industry participants to cooperate on the development of shared mappings and/or to work with terminology developers (e.g. AMA for CPT codes) to develop shared mappings as part of their code maintenance process."