Each registered model version must be assigned a unique, non-reusable identifier. This requirement ensures that a model version, once registered, cannot be overwritten, replaced, or confused with another version. The identifier is the anchor for the entire traceability chain: it is referenced in inference logs, deployment records, the AISDP, and the Declaration of Conformity.

Immutable versioning means that once a model artefact is registered under a given identifier, neither the artefact nor its identifier can be changed. If the model needs to be updated, a new version is registered under a new identifier. The previous version remains in the registry under its original identifier, available for retrieval throughout the ten-year retention period. This approach prevents the scenario in which a model is silently replaced in the registry, invalidating all references to the original version.

The immutability guarantee should be enforced at the registry level, not merely by policy. MLflow, SageMaker, and Vertex AI model registries all support version immutability through their native access control mechanisms. Organisations should verify that the registry’s configuration prevents overwriting or deletion of registered versions, and that administrative overrides are logged and auditable. A model version identifier that can be reused or overwritten undermines the entire compliance record.

Key outputs

• Registry configuration enforcing version immutability
• Verification that identifiers cannot be reused or overwritten
• Administrative override logging
• Module 10 AISDP evidence