Suspicious Activity Report (SAR)

A suspicious activity report, also called a suspicious transaction report, is the confidential filing a regulated crypto firm submits to its national financial intelligence unit when it knows or suspects that funds relate to criminal conduct. The trigger is suspicion, not proof: patterns such as structuring deposits just below reporting limits, rapid pass-through of funds, inconsistent explanations of source of funds, or links to addresses associated with fraud can all lead to a filing. Reports are normally confidential, and staff are usually prohibited from telling the customer that one was made — a restriction known as tipping-off. Filing does not by itself freeze an account, though a firm may separately suspend activity while it reviews. Rules vary by jurisdiction.