Mass update Account ownership with Data Loader

To change the child records such as Contacts for an Account, perform the following procedure:

1. Create a report on Accounts that includes the fields Account Owner, Account ID and Account Name. Optionally, add additional fields that may help you to identify the Accounts to be transferred.
2. Export the report as a .csv (comma-separated values) file.
3. Sort the resulting report export's .csv file in Excel by Account Owner.
4. Next you will need to replace the existing Account Owner's name with the new Account Owner's Salesforce User Id. Locate the new owner's User Id in Salesforce by navigating to Users from Setup.
5. In the list of Users click on the User's name that you'd like to transfer Account ownership to.
6. Copy the Salesforce Id for that User from your browser's URL (15 or 18-digit ID beginning with '005').
   
   • In Lightning after enabling My Domain, the URL might read: https://<mydomain>.lightning.force.com/lightning/setup/ManageUsers/page?address=%2F005bm000004MyfH%3Fnoredirect%3D1%26isUserEntityOverride%3D1 where "005bm000004MyfH" is the User Id in the string and there will be random number and letter combinations following the "005" for each user in your organization.
   • In Classic after enabling My Domain, the URL might read: https://<mydomain>.my.salesforce.com/005bm000004MyfH?noredirect=1 where "005bm000004MyfH" is the User Id in the string and there will be random number and letter combinations following "005" for each user in your organization.
7. Paste the new owner's User Id over the existing Account Owner name values in the Excel file. Note: If you are transferring ownership to more than one user, you can create a report on active Users to get the User Id for all the Users in one sheet for multiple transfers.
8. Once the existing Account Owner's names have been replaced by your new owner's User Ids, save your file and it is now ready for import.
9. Open Data Loader and click Update.
10. Login to the production or sandbox where you want the change to take place.
11. Select Account for the object and browse for the .csv file for import.
12. Map the columns to fields:

• • Map your field: Account ID to ID
  • Map your field: Account Owner to Owner ID

13. Click OK and then Next.
14. Start the import.

To automatically update the associated child records to the new owner, use the Mass Transfer Records tool.