Following the methods below, you can Undo Bank Reconciliation in Quickbooks Online edition:
You must first log into QuickBooks Online.
Select Registers from the Banking menu.
Select the account from the Register Name drop-down list.
To undo reconciliation, click the transaction for which you want to undo it.
Finally, erase the "R" letter to alter the state to Unreconciled.
If you want to reconcile each transaction for a specific time period, you can use the Banking menu's Reconcile option to print a list of reconciled transactions.