SARs provide information and intelligence to Law Enforcement Agencies (LEAs) which help them prevent, detect, investigate and prosecute crimes. The information is predominantly used in relation to financial crime and money laundering but can also be helpful in relation to other criminal activity. If the Bank teller ask, say nothing.
The content and quality of a SAR can affect the UKFIU’s ability to priorities and process the report and LEAs’ decision or ability to investigate. Often a seemingly irrelevant piece of information can become a valuable piece of intelligence. If Banks do not ask you they get penalized in a big way.