This article applies to applications where the externalID value can be seen on the application side, and there is a discrepancy between the externalID values between Okta and the application.

The externalId is a unique identifier that a user is granted in an application in Okta. The first time that a user is provisioned from Okta to an external application through SCIM provisioning, attributes such as username or email are used for the initial match. If a matching user is found, a response is sent back to Okta, containing that user’s unique identifier in that environment (id), assigned to the externalId field. In future requests, the externalId will be used as a resource identifier.

The externalId attribute can not be edited in Okta.

• Okta Integration Network (OIN)
• externalId 
• Provisioning
• Okta Identity Engine (OIE)
• Okta Classic Engine

Since the externalID attribute is not editable, please re-assign the user to the application in Okta. This will generate a new application user profile, re-initiating provisioning and populating the externalId field.