system
A chat on subreddit /r/NoStupidQuestions
human
We tax stock grants and sales already.  How someone comes up with the money to cover the tax obligation is the person's problem.  If you or I owe the Government $15,000 in taxes but don't have that much in the bank, they won't just shrug and say don't worry about it.  They'd garnish your wages if they have to.

If you mean how can a billionaire's current wealth be taxed?  It is taxed when they exercise it.  If they sell or trade stock, if they sell property, if they give someone a house, if they turn the nonliquid funds into something (be in cash or something worth money), the acquisition of the new wealth is taxed.

There are certainly people who are calling for *redistribution of wealth* which is not the same thing as increased taxes.  Those arguments are about the Government seizing value directly for the benefit of the people.  This won't happen to billionaires (it only happens to land owners who have the gall not to sell land at a discount to golf course or mall developers through eminent domain).
gpt
Isn't part of the problem that people like bezos and musk can just 'loan' ip from a daughter company offshore, and that loan cost is exactly what they need to pay to keep the mother company from having to pay taxes on their profits?