The fundamental problem is that wealthy people have their wealth in assets and their cash comes in loans. The best I can come up with is a tax on loans larger

The fundamental problem is that wealthy people have their wealth in assets and their cash comes in loans. The best I can come up with is a tax on loans larger than X with assets that meet the points ABC used as collateral. On the other hand though, I can make a case that they shouldn't be taxed anymore as it is. The assets they hold generate the majority of the taxes collected anyway. Bezos might not pay a lot in taxes, but amazon does and the amount it generates in sales taxes and income taxes is enormous. It's a difficult problem and it's why progress has been stagnant in this area for decades.