In our institution, during initial and annual training, all bank staff are instructed to report suspicions to our Internal Auditor (our designated SAR reporter). That can take the form of an email, a phone call, a memo or a visit to his office. From that point, he interviews the reporting person for the appropriate details and then carries forward from there.
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"No problem can withstand the assault of sustained thinking." ~ Voltaire
"Sustained thinking gives me a headache." ~Me