We don't deal with brokering, but the way I understand the purpose of the NMLS # is so that the consumer can make an educated choice about what MLO they want to use. The consumer can check up on the person they are dealing with to make sure they are comfortable with their experience, affiliations, etc. So with that understanding, I would include the NMLS # of the MLO who is communicating with the customer. Who is the customer going to call to ask questions, etc? If you are mailing correspondence directly, whose name are you putting on the correspondence? If someone from your insitution, then use their NMLS #.
Hope that helps.
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I can't herd the cats anymore, so I just set up the electric fences and let them fry when they stray out of bounds.