Q: Does FinCEN permit voluntary SAR filings?
A: Yes. In addition to required SAR filings, financial institutions may also file with FinCEN a report of any suspicious transaction that it believes is relevant to the possible violation of any law or regulation but whose reporting is not required by 31 CFR Chapter X. A voluntary filing does not relieve a financial institution from the responsibility of complying with any other reporting requirements imposed by the SEC, the CFTC, a self-regulatory organization (SRO) (as defined in section 3(a)(26) of the Securities Exchange Act of 1934, 15 U.S.C. 78c (a)(26)), or any Registered Futures Association (RFA) or Registered Entity (RE) (as these terms are defined in the Commodity Exchange Act, 7 U.S.C. 21 and 7 U.S.C. 1a(29)).
This is addressed in the "FinCEN Suspicious Activity Report Electronic Filing Requirements" guide, Attachment C.