If a posting has been reversed, the item on the Bank Reconciliation shows on the same side but has a minus in front of it. For example, if it is a Nominal Receipt, the reversal shows as a minus credit.
The Bank Reconciliation can sometimes have reversals that don't have the original entry to reconcile against,
If this is the case please check the below details:
Take a look at the original transaction and drill down into the posting on the Accounts Ledger to see what bank rec this was reconciled on.
Once you find the bank reconciliation statement number, look at what went through the bank statement to see if some money was transferred to reconcile.
If no money was transferred, then check what transactions were on the Cash book that the transaction could be reconciled with.
If money was transferred then this will need transferring back for the reversal. If there was an incorrect posting that the transaction was reconciled with then a correction will need to be done to rectify why the two items were reconciled together.