I don't think you can change it. If you need to reconcile it then you can do so manually, set up a new account with the ability to reconcile and transfer the balance, you can then reconcile the account from then on.
-- Edited by Rhianrach on Tuesday 22nd of January 2013 04:07:01 PM
Please can someone tell me if it is possible to change the bank reconciliation setting on a bank account in Sage after the transactions have been posted? i currently have a small bank account that originally was marked as don't reconcile and now the box is greyed out so I can't change it so that I can reconcile it.