Change the External ID of Existing Employee Record

External IDs are created at the time of record creation or during a record update operation. They are explicitly created using web services and are not generated by the system. The external id is specified in the SOAP request when the record is being created or updated. 

External IDs can only be updated or changed via a CSV Import.  Follow the steps below to do this:

1.  Create an Employee Search to include Name, Internal and External ID. 

2.  Export the Employee search as a CSV file. Click on the link to see the steps on how to Export Search to CSV

3.  Edit and update the External ID column > Save file in your computer.

4.  Import the CSV file by navigating to Setup > Import/Export > Import CSV Records. Click on the link to see the steps on how to  Import CSV File with CSV Assistant
     a.  Import Type: Employees
     b.  Record Type: Employees
5.  Select the file from your computer > Next.
6.  Data Handling – Update (choose Add if this is the first time to enter the External ID)
7.  Map the following in the Field Mapping page:
     a.  Internal ID
     b.  External ID
8.  Click on Next.

9.  Save mapping and start import then click on Save & Run.