substitutionIt could be unwise to assume all UK implementations will prevent substitution if not explicitly stated, especially if the same clinical system has been previously implemented outside the UK.
Within UK Core this element is mandatory and SHALL have a boolean value of false to denote that substitution is not allowed, unless substitution can occur in a specific case.
Where substitution to be be allowed, set to true. The inclusion of the coded reason is optional as the valueset defined in FHIR is of limited benefit to UK healthcare.