Fixing Import Errors: MALFORMED_ID

To fix this error, change the ID in your CSV file

Obtain ID From Report

1. Click the Reports tab in the navigation bar
2. Click New Report
3. In the Search Report Types search bar, type the name of the object you are importing into
4. Click the search result for the object you are importing into
5. Click Continue
6. Click the Filters column and ensure All records are shown for All Time
7. Click the Outline column
8. Remove all fields from the Columns section except the record / object Name 
9. Add the record / object ID under the Columns section
10. Open the error csv file you received as an attachment in the summary email after the initial import
11. In the error csv file, change the ID in the cell identified in the error message to an existing ID shown in your Salesforce report
12. Save the error csv file
13. Perform the import again using the error csv file

Obtain ID From Record

1. Type the record name in the Global Search bar on the top of the screen
2. Click the search result for the record
3. In the URL bar you will see the ID for the record
   • The URL will look similar to this and the ID is shown in bold 
     • https://<YourInstanceOrMyDomainHere>.lightning.force.com/lightning/r/Case/5003000000D8cuIQAA/view?0.source=alohaHeader
4. Open the error csv file you received as an attachment in the summary email after the initial import
5. In the error csv file, change the ID in the cell identified in the error message to the existing ID shown in your Salesforce record URL
6. Save the error csv file
7. Perform the import again using the error csv file

For more information on errors that can be encountered within Salesforce, what they mean and how to fix them, please review the following resources:

1. Core Data Types Used in API Calls
2. Fix Data Import Errors in Salesforce Essentials
3. Reports and Dashboards
4. Find the Salesforce ID for a Record
5. Data Import Wizard