When you need to inform Law Enforcement of an activity going on, before you file the SAR, how much and what information are you allowed to tell them?

File the SAR ... then tell them.

Being stupid here. You mean file the SAR, then call them, because techinically then you can tell them everything in the SAR? Sounds good.

If you need to notify them before you have time to file a SAR, here is an excerpt from the RFPA.

§ 3403. Confidentiality of financial records

(c) Notification to Government authority of existence of relevant information in records.

Nothing in this chapter shall preclude any financial institution, or any officer, employee, or agent of a financial institution, from notifying a Government authority that such institution, or officer, employee, or agent has information which may be relevant to a possible violation of any statute or regulation. Such information may include only the name or other identifying information concerning any individual, corporation, or account involved in and the nature of any suspected illegal activity. Such information may be disclosed notwithstanding any constitution, law, or regulation of any State or political subdivision thereof to the contrary. Any financial institution, or officer, employee, or agent thereof, making a disclosure of information pursuant to this subsection, shall not be liable to the customer under any law or regulation of the United States or any constitution, law, or regulation of any State or political subdivision thereof, for such disclosure or for any failure to notify the customer of such disclosure.