Decision Use the capital case bolded SHOULD whenever providing conformance rules and guidance is as defined in FHIR R4  __  A best practice or recommendation to be considered by implementers within the context of their particular implementation; there may be valid reasons to ignore an item, but the full implications must be understood and carefully weighed before choosing a different course.   Background   The intent was to differentiate the conformance verbs "SHOULD" as defined in FHIR R4 for conformance rules from a  lower case "should" for implementer guidance that is a non testable best practices. e.g., SHOULD: "The following search parameter combinations SHOULD be supported. SHOULD support searching using the combination of the patient and clinical-status search parameters: should: "For any other references to base FHIR resources1 or not formally defined in a US Core Profiles, the referenced resource should be a US Core Profile if a US Core Profile exists for the resource type" Rationale However the FHIR definition of  "SHOULD" is as a best practice or recommendation that implementers should consider, but it is not a requirement that is strictly enforced. This means that while it is recommended to follow the "SHOULD" statement, it is not required, and there may be valid reasons for an implementation to choose a different course.  As a result, "SHOULD" statements can be considered the same as "should" in the context of implementer guidance. Both are considered non-testable best practices because they are not directly testable and must be evaluated within the context of the implementation.    Please note that we have used OpenAI's chatCPG to assist in answering this question. We review these responses, and the information provided is based on our experience, implementer feedback, and our design choices for US Core.