If (and only if) blockchain become mainstream then maybe the tax system would be like ICO DAO system, there will be proposals, people vote on smart-contract, then fund release if cap reached. Otherwise, the government would simply use old the old tax system. They will simply impose taxes on exchanges.
My bad, bounties ruin my brain.
Just no!
ICO's have screwed enough people already, we don't need an ICO to ruin an entire country.
You don't need tokens or crypto or a blockchain to run a modern tax system. The blockchain is a simple distributed database, we already have those in almost every developed country, no need for fancy words schemes.
C'mon man, no need to explain what is blockchain to me.
When cryptocurrencies used in the everyday transaction (perhaps replacing fiat), the government will lose control of money, they couldn't force people to pay taxes. Therefore, governance would be similar to decred, smart cash, etc., with proposals (vote using smart contract).