Presumably physical collectible assets (maybe also virtual ones too for the NFT crowd) will be assessed differently from more liquid assets for the basis of evaluating a wealth tax, especially in the event of surging valuations from the collectibles market. If real life taxes, like say property tax in California, can be reined in by measures like Proposition 13, then there's no reason why a real-life wealth tax won't be subject to all sorts of internal controls and effects from lobbying. Thus protecting the "run of the mill average Joe" from having to suddenly sell his mythical rock.
What about surging valuations in the equities market? If I'm worth $1B for a few moments because of a surging valuation, and then the government takes $900M of that, and then the stock crashes back to 1/100th of its peak, do I get my shares back?
Just as current income taxes have a hard deadline in which financial assets are assessed, your extreme edge case is only applicable one day a year, rendering it ever the more trivial.
Not to mention, the calculation for wealth would probably be based on something less temporary than a fleeting moment in the markets.
Finally, the government would not directly take shares, so they would always be owned by you. Presumably with the stock price so much reduced you can simply purchase more at a pittance.
I'm not sure if I would particularly care that it was just an edge case that caused me to miss out on $99M.
They wouldn't take shares, but I would be forced to sell shares in order to pay the tax bill, because I don't actually have that money just laying around. So I had 10M shares @ $1/share, share prices go up to $100/share. I get hit with a $900M tax bill and sell 9M shares in order to pay it. Price goes back down to $1/share, leaving me with 1M shares. How exactly should I purchase more at a pittance? I spent all the money I didn't even have paying the tax bill, there's nothing left in my bank account to buy any shares.
