Why the sync error occurs
This error occurs when a deleted account in Bill.com is trying to sync to QuickBooks Online, but the account is one of the special accounts QuickBooks Online needs to operate, such as Uncategorized Income and Uncategorized Expense.
How to fix the sync error
These accounts can't be deleted or edited in QuickBooks Online. The only options are to reactivate the deleted account in Bill.com or to contact Customer Support to clear the error.