Together with some major bills for insurance and healthcare, that's all they get.
So I can hide cash under the bed, or have an overseas account, or have some Gold bars, etc. The goverment has to thrust me quite a bit.
They can check some transfers, but if you like to hide it, you can do it.
So the actual way of getting the real numbers is quite bad.
In Bitcoin
If the Tax department makes it a rule by law, that you have to report every BTC address you own, or every wallet you own ...
All problems solved, because then the Department has also the addresses of the petrol station and the deli you spend money.
In no time the system knows which tax counts here and can claim the respective amount from both sides.
Sure it is still possible to hide Bitcoins, but then it is illegal.
...or did I miss something?
So in my opinion there should be another wallet by the government for the Bitcoin and each wallet is verified with the eKYC verification .
So that every detail will remain in the single wallet and then no one need to track , they only need to see that how much he made received and sent and how much he made profit . In this way they can easily apply the tax for the earnings .