+The following principles apply to the definition and use of identifier systems within UK Core–conformant implementations:
+
+
+- Uniqueness is the primary requirement for an identifier system, although excessive specialisation reduces long‑term usefulness and semantic value.
+
+
+- Identifier systems SHOULD NOT carry meaning. Consumers SHOULD NOT derive semantics from the structure or contents of the system or value. Identifier systems exist solely to establish uniqueness and scope.
+
+- Ownership of identifiers SHOULD be clear.
+Ideally, the system generating the identifier is represented by a unique identifier system URI. Where this is not possible, the organisation that owns and manages the identifiers should be considered the authority for that system.
+
+
+- Identifier system URIs MAY change over time.
+Implementations SHOULD NOT assume system URIs are permanently resolvable or immutable. Most healthcare data has a limited operational lifespan, and identifier systems may evolve accordingly.
+
+
+- Use of the NamingSystem resource is OPTIONAL.
+NamingSystem resources are intended for historical reference and documentation only. Implementations SHOULD NOT rely on the presence of a NamingSystem for runtime processing or validation.
+
+
+- Do not rely on assigner or type for processing or search.
+Best practice is to avoid dependence on Identifier.assigner or Identifier.type, as neither element is reliably searchable across implementations.
+
+See DataTypes - Identifier and
+
+
+
+
+
+
+
+ {{page:Profiles-Table}}
+
+
+
+ {{page:Derived-Profiles-Table}}
+
+
+
+ {{page:Profiles-Table-With-Purpose}}
+
+
+
+ {{page:Derived-Profiles-Table-With-Purpose}}
+
+
+## Derived Profiles
+
diff --git a/guides/UK-Core-Implementation-Guide-STU3-Sequence/Home/Terminology/Terminology-Index.page.md b/guides/UK-Core-Implementation-Guide-STU3-Sequence/Home/Terminology/Terminology-Index.page.md
index ab52cfa2b..97b946aae 100644
--- a/guides/UK-Core-Implementation-Guide-STU3-Sequence/Home/Terminology/Terminology-Index.page.md
+++ b/guides/UK-Core-Implementation-Guide-STU3-Sequence/Home/Terminology/Terminology-Index.page.md
@@ -18,6 +18,28 @@ Other ValueSets are usable if the binding strength is defined as extensible. For
Within this release of the UK Core, ValueSet expansions have been incorporated into the ValueSets. For some ValueSets containing SNOMED CT or dm+d data in particular, the number of concepts were deemed too large to expand. It should also be remembered that the expansions of SNOMED CT data in particular represent the content available at the time the expansion was generated, but that this content can subsequently change. For an up to date and complete list of values, suppliers SHOULD consult the latest SNOMED CT terminology release.
+
+
SNOMED CT UK Edition
+
+The FHIR UK Core terminology bindings utilise the UK Edition of SNOMED CT. This edition includes the International release of SNOMED CT, supplemented by UK-specific clinical concepts, reference sets, and descriptions that reflect the needs of health and care services across the United Kingdom.
+
+
+UK Core mandates the use of SNOMED CT, specifically the SNOMED CT UK Edition, for all clinical concepts where SNOMED CT is indicated.
+All UK Core profiles, value sets, and examples that reference SNOMED CT SHALL be interpreted using the SNOMED CT UK Edition.
+
+SNOMED CT International URI:
+ `http://snomed.info/sct`
+
+SNOMED CT UK Edition URI:
+ `http://snomed.info/sct/83821000000107`
+
+
+Implementations claiming conformance to UK Core SHALL support the latest version of the SNOMED CT UK Edition and any UK‑specific reference sets used by UK Core artefacts.
+
+The latest release can be accessed via:
+- the [The NHS England terminology server](https://digital.nhs.uk/services/terminology-server), or
+- the [NHS England TRUD](https://isd.digital.nhs.uk/trud/users/guest/filters/0/home) (Technology Reference data Update Distribution) service
+