The first thing you need to do is properly define what constitutes an "indirect MRB."
The consulting firm CRB Monitor developed the three-tiered approach several years ago, which has been so commonly adopted that industry colleagues I've spoken with have - at times - assumed that it had stemmed from regulatory guidance.
In my humble opinion, the "three tier" framework as originally presented is needlessly complex and also not as well defined in detail as expected. But the spirit of the framework is great. And by that, I mean the concept of three large levels of risk relative to MRBs is appropriate.
Getting back to defining them, I'd suggest focusing on those entities which provide either a service/product that is unique and essential to the marijuana cultivation process, provide a physical location (i.e. landlords), and provide some sort of direct non-bank financial service to them (e.g. transaction processing, investing, private loans, etc.). Why? Those are the entities which, if you're a "moderate" relative to your interpretation of the Controlled Substances Act, would require SARs.
But as the previous poster had indicated, organizational risk tolerance and the accompanying interpretation of the CSA play into your decisionmaking. If you're a "strict" constructionist of the CSA, then you'd treat nearly all indirect marijuana-related entities just like you'd treat an "indirect cocaine-related business" or a "Tier II Heroin Company." On the other end of the spectrum, I've observed financial institutions that don't file SARs based on "indirect MRB" status alone, have received "support" for that stance from FinCEN's resource center, do no real EDD beyond flagging them, and have had ZERO problems with regulators (yet). I'm not advocating that approach, but illustrating just how "plastic" the expectations are in this area.
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CFE, CAMS