If you impose a wealth tax on this, which side are you imposing it on? Company or individual investor in the company? You cannot impose a tax on what is technically a liability on the company's books. So you would have to impose on the individual investor. Lets try with an example: assume the wealth tax is 10%. Lets also assume I hold 5 million common stock, pre-seed, in a startup I founded (45% equity). How would the stock be valued? It should be zero. So I pay zero wealth tax. Then I get an investor onboard, who invests say $1 million at 10%, valuing the company at $10 million. Lets assume, because of this capital infusion, my equity gets diluted to 40%. That means I am on paper worth $4 million. I immediately owe 10% of it or $400,000 to tax authorities. Without having made a single cent in revenue. My co-founder would also owe $400,000. We have no money of our own except to use the investment money to pay the taxes. That is $400,000 + $400,000 = $800,000. We are left with only $200,000 in the bank. Before we even started the company.

You might say 10% is too much. Lets reduce the wealth tax to say 1%. Or even 0.1%. Then the entire idea becomes meaningless. Might as well just charge extra corporate tax.