> You are asking me about implementation difficulty, difficult implementation doesn't mean idea is not worth it.

I can agree with that idea, to an extent. If something is near impossible (not saying this is), then it does become not worth it.

The other questions the parent posed are more interesting to me:

> How would you determine the worth of rare, illiquid or intangibles? What about wealth held in trusts or companies? How does the accounting work if I borrow against my wealth? What happens when things change value dramatically in a short period of time?

Another I wonder is that (ignore all specifics of the values, just the concepts matter here), let's say you own a private business that then becomes valued at 1.5 billion dollars and this individual has 20 million dollars liquid. How do you tax that? The government can't take one third of the business, at least not without a lot of issues (in business dealings and individual rights), and the 20 million liquid wouldn't come close to what this plan would value. What do we do then? Plenty of billionaires don't really have liquid cash and forcing liquidation of assents in such a way seems like it would be very difficult.

I'm all for more taxes on higher net worth individuals, but I think there's a lot of talk to be had on how one can implement this. It's going to be really difficult to find a way that makes sense.

> I can agree with that idea, to an extent. If something is near impossible (not saying this is), then it does become not worth it.

FATCA law makes this very possible in the US.

> How do you tax that? The government can't take one third of the business, at least not without a lot of issues (in business dealings and individual rights)

I would say that the government can and should and simply be a passive share holder with no voting rights.

Obviously, I do not know nitty gritty details of economy and finance, but if I would implement this tomorrow I would start taking the equivalent of surplus and start from there to understand more.

For example, say individual has 20M liquid cash, 2 houses each valued at 5M and 1.5B in company shares (based on averaged company value for the last 6 or 12 months):

* whatever you can immediately spend is prioritised first, so you keep your 20M + 2 houses, then surplus is $530M of your company shares

* this equivalent number of shares will be moved to government trust, individual doesn't have any control over it, if person dies next day, government keeps the money (lets simplify for now and keep voting rights as separate question)

* let's say after shares moved to gov. trust, during next 6 months company value halved, gov. returns all your shares, if stock dropped only 10%, you get equivalent back to make your net worth 1B

* regarding taxation, I would keep it as it is today and tax on "realization event"

There are around 3.000 billionaires in the world, even hiring 10 dedicated people for each billionaire to calculate all this stuff on a quarterly basis is not expensive