The Financial Conduct Authority says NatWest allowed increasingly large cash deposits to be lodged in a customer’s account that should have alerted suspicions.
It is alleged that around £365 million was paid into the customer’s accounts, of which £264 million was in cash.
The FCA claims NatWest “failed to adequately monitor and scrutinise this activity”.
NatWest is scheduled to appear at Westminister Magistrates Court on 14 April.
It is the first time the FCA has ever launched a criminal prosecution under the 2007 Money Laundering Regulations and the first time the rules have been used to prosecute a bank.