The exchange should be the one who's responsible in each transactions that we do inside our crypto business, just like what you have said most of the users are anonymous and they can hide their identity as what's the main goal of crypto so in behalf those registered exchange should take the responsibilities in order for government to acquire decent taxes as well from this market.
There are some problems for the exchanges to charge tax from users:
- The Exchanges trading fee is depending on the crypto-currencies trading pair, not on fiat, so it's hard to calculate how much tax that the exchange have to pay.
- The price of crypto-currencies is not stability, u have 2 bitcoins right now doesn't mean u get profit from trading this year, since you started from buying 1 bitcoin for $19k before.