If you're looking for a rough overview of how US business income taxation works -- and who isn't really -- this is an interesting article by Matt Levine. He has a knack for making this stuff a lot more interesting. The real purpose of the article, though, is as a lead up to talking about Biden's proposed "billionaire minimum tax". At the highest level, here's the idea:

His most recent budget would require taxpayers worth more than $100 million to pay a minimum of 25% on their capital gains each year, whether they sold assets for a profit or continue to hold them.

The way things work today is that unrealized capital gains are not taxed. Meaning you can own something like a stock for a really long time and not pay any capital gains on it, until of course you sell or realize the gains. So this is a philosophical kind of change. And in Matt's words, it is both "jarring" and "possibly unconstitutional".

But I guess it doesn't affect that many people. There are, according to CNBC, somewhere around 10,660 centi-millionaires in the US. I wonder why it's not called a centi-millionaire minimum tax, though. (I know why.)