A report that financial firms must file with regulators when they detect a suspicious transaction that may indicate money laundering or fraud. For forex brokers, any large, unusual or structuring transaction that does not fit a client’s profile should trigger a SAR. Once a trade is flagged, the broker “is obligated to file a Suspicious Activity Report (SAR) with the relevant regulatory authorities,” providing details of the suspect transaction and parties. Financial authorities (e.g. FinCEN in the US, FCA in the UK) use SARs to investigate financial crimes.