Troubleshoot list damage in your QuickBooks company file if, after verifying data, the Verify Data utility displays the following error:
The QBWin.log contains the same error in detail and shows you the duplicate names found.
Various types of "Duplicate names encountered" errors in QBWin.log:
QuickBooks detects these errors if two or more names in your lists are identical. Duplication in lists can occur when importing lists or transactions either from a different company file, from Excel, or other integrated applications.
IMPORTANT: Rebuilding your company file can help resolve damaged list elements. If errors remain after rebuild, find and edit the duplicates to resolve the problem. Before you proceed, back up your company file.
Step 1: Find the duplicate names
Step 2: Edit one of the duplicate names
After modifying the duplicates, determine if you need to keep the modified names separated. If they do not have any transactions associated with them, you can try to delete them. Otherwise, you need to merge the names.