The base R4 EOB,  EOB.provider is a reference to (Practitioner | PractitionerRole | Organization). The base CARIN ExplanationofBenefit profile has Reference(CARIN_Blue_Button_Organization_Profile.    The CarinBBEOB profile will constrain the reference to (CarinBBPractitioner || CarinBBPractitionerRole || CarinBBOrganization).   In the mapping that drove the CarinBB IG, the EOB.provider is the 'Party responsible for the claim'.   This varies for the different EOB subtypes, as follows: For Facility (Inpatient and Outpatient) Claims), this must be an Organization. For Professional/Non-Clinician and Pharmacy claims, this may be an Organization, Practitioner, or PractitionerRole. The Inpatient/Outpatient Facilitiy EOBs will constrain provider to CarinBBOrganization.