Why the Sync Error occurs
This error occurs when QuickBooks preferences are set to prevent the invoice number of the bill or reference number of an offline payment to be reused if it has already been used for the same vendor.
How to Fix the Sync Error
If the error is for a bill:
- Locate the bill
- Click More actions
- Click Edit bill
- Update the invoice number to something not yet used by the vendor
If the error is for an offline payment:
- Locate the payment
- Click Void payment
- Record a new offline payment with a different reference number
Alternatively, adjust the QuickBooks preferences to allow for the use of duplicate invoice or payment fields.