QuickBooks Online sync error: You must specify a different number. This number has already been used
Why the sync error occurs
This error occurs when the reference number (Ref#) on a Key CashFlow offline payment is already in use within QuickBooks Online or has been entered on a payment that is for more than one invoice.
How to fix the sync error
Void the offline payment and record a new offline payment with the correct reference number.
- Select the Payment confirmation number from the sync status page
- Select Void payment
- Select Yes to confirm
Record a new offline payment for the bill(s).
Alternatively, record the payment manually in QuickBooks Online and contact Customer Support to request the sync error be cleared.