Out of Curiosity Bill, If someone files a Schedule C, weren't they required to receive a 1099 from at least some of the entities he received income from? wouldn't those 1099's disclose who the income was from? I know when I was in business for myself, I didn't get 1099's from all of my clients, but I did have to send out 1099's to the Consulting Engineers and people I contracted with to help do drafting work for me.
In Hunter Biden's case, I'll go out on a limb and say that it's highly doubtful he paid taxes on much of that filtered and laundered income he received.