diff --git a/specification/components/schemas/pdsEventData.yaml b/specification/components/schemas/pdsEventData.yaml
index 2bdcf0b..cd16b93 100644
--- a/specification/components/schemas/pdsEventData.yaml
+++ b/specification/components/schemas/pdsEventData.yaml
@@ -3,13 +3,12 @@ description: ""
 required:
 - fullUrl
 - provenance
-- registrationEncounterCode
 - versionId
 properties: 
   versionId: 
     type: "string"
     example: 'W/"2"'
-    description: "The versionId/ETAG identifies the version of the resource."
+    description: "The versionId/ETAG identifies the version of the resource. The format should be a version identifier enclosed in quotes and preceded by 'W/'."
   fullUrl: 
     type: "string"
     example: "https://int.api.service.nhs.uk/personal-demographics/FHIR/R4/Patient/9912003888"