I'm imagining that the wealth tax would only apply to people with more than $1bn in net assets, so the overhead for almost every tax payer is to simply tick a b

I'm imagining that the wealth tax would only apply to people with more than $1bn in net assets, so the overhead for almost every tax payer is to simply tick a box each year saying "I am not a billionaire". More precisely, the law would require anyone with gross assets above some threshold, say $500m, to report the value of those assets to the IRS every year, based on some simple valuation rules, like "How much did you pay for the asset?" and "What is the market value of those shares / cryptocurrencies?". Only assets worth more than $1m would need to be declared. Then, as I say, the IRS can go down the list of people with the most assets and do a more thorough audit, to make sure their valuations are correct, while also making sure that there aren't any billionaires who have forgotten to file, since it should be hard to hide that much wealth.