Assets are taxed all the time (real estate tax, car tax… ). So taxing the value of a share portfolio at the 31st of December each year is perfectly doable. And if it has depreciated since last year, you get a tax deduction… which is capped by the income tax to maximally reach 0… No carrying over till next year… or maybe 1 year… whatever, that’s implementation details.

How much do you tax these assets is the point that needs consideration… it’s not fully income… But a percentage is only fair. And if this means people need to realize gains to pay for it… that’s fine… Why would it not be?

And borrowing against an asset portfolio should mean that it counts as realizing gains of the asset portfolio and the amount is seen as income and thus taxed. (You loan 10 million against your shares, that’s income) And to avoid fallout for the normal people you can build in a threshold and exclusions for example for the first million in your lifetime… or for the mortgage on your primary residence with a cap at the median house price or … something. So for these people borrowing against assets means they can keep the assets… but pay interest on the loan. Alternatively they can actually realize the gains and pay cash.

It’s not hard at all, it’s a matter of political will, and writing proper laws that state your objective and exceptions.