Why the Sync Error occurs
This error occurs for various reasons and is related to updates made to vendors or accounts.
How to Fix the Sync Error
Payment was recorded manually Delete the manually recorded payment from QuickBooks, which will allow the payment record from Bill.com to sync to QuickBooks in a subsequent sync. If the bill cannot be deleted from QuickBooks manually, contact Customer Support to request that the payment be marked not to sync.
Bill no longer exists in QuickBooks Contact Customer Support to request that the record updated in Bill.com be marked not to sync. After the record is marked not to sync, record a manual update in QuickBooks.