"Customer:Job: XYZ is duplicated in the QuickBooks file," where XYZ indicates the Customer name that is causing the error.
This message appears because a Customer name exists under the same name either as a Customer, Vendor, Other Name, Employee, or Item in the QuickBooks Desktop (QBDT) company file. This may occur because IIF tools have been used, and these tools bypass the data validation in QBDT. It may also occur as the result of an index corruption.
Step 1. Check for the Customer name in other QB lists (Vendor, Other Name, Employee, or Item). Be sure to include inactive names when searching.
Step 2. Try renaming the Customer that is failing to import in QBDT and then rename it back to the correct name.
Step 3. Do a rebuild of the QBDT file (File > Utilities > Rebuild Data)