I imagine it is like anything else: they don't know, but if they do an audit or another agency is investigating you for something else and they notice, then they start investigating it.
I do think it is fair to say that there are more than 802, apparently, people in the United States in 2016 that mined/bought/sold bitcoin so they definitely see there is a problem.
I do think it is fair to say that there are more than 802, apparently, people in the United States in 2016 that mined/bought/sold bitcoin so they definitely see there is a problem.