FinCEN writes and administers the anti-money-laundering rules that brokers, banks, money services businesses, and many crypto firms must follow. It receives the suspicious-activity-report and currency-transaction-report filings the industry generates, and shares that intelligence with law enforcement.
Its rules are the reason your broker asks intrusive questions at onboarding: the customer-identification-program and customer-due-diligence requirements flow from the bank-secrecy-act through FinCEN regulations.
Filing is confidential and one-directional. A firm may not tell you that it filed a report about your activity, which is why an account can be restricted or closed with no meaningful explanation.
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