A suspicious transaction report (STR) is a mandatory document that reporting industries, such as financial institutions, must file with the relevant financial intelligence unit (FIU) when they detect suspicious activity — potential cases of money laundering and other types of fraud. In other words, they must file STRs when a transaction is detected which can be connected to illegal activities. This term is also often used interchangeably with a suspicious activity report (SAR), depending on the jurisdiction.
STRs serve as red flags, helping regulators and law enforcement take appropriate action. This is important, as unusual activity could indicate illegal actions threatening public safety or the overall transparency of the general financial system. So, using this reporting system helps alert authorities while providing valuable insights for identifying and preventing financial crime.