Suspicious activity, in anti-money laundering usage, is any conduct by a customer, or any transaction or pattern of transactions, that gives a bank or other regulated business grounds to suspect involvement in money laundering, terrorist financing, fraud, sanctions evasion or other crime. It need not be proof of wrongdoing; the legal test is usually suspicion, or reasonable grounds to suspect, based on what the firm knows about the customer.
Common signs, often listed as a suspicious activity indicator, include transactions with no clear business purpose, activity inconsistent with the customer's profile, cash deposits just below reporting thresholds, rapid movement of funds through an account, and reluctance to provide information. Firms detect it through staff observations and transaction monitoring, investigate alerts, and, where suspicion remains, file a suspicious activity report or suspicious transaction report with the national financial intelligence unit, without alerting the customer.