Certainly if you were lodging or withdrawing large volumes of cash, then a bank would be obliged to report it under money laundering legislation.
Why? Say I take 20g from TSB and want to put it in Ulster Bank. Its my money, its legit, so why do they need to tell revenue? Revenue know from the DIRT anyway?
Banks, building societys, credit unions etc are required to notify revenue of transactions in particular situations. May transactions can be traced back and there is no investigation performed. This requirement came from anti money laundering requirements and any ordinary person has nothing to fear.
Regards
Mike