Tax on any obtained profit resulted from   crypto related activity ^{sell, exchange, pay for goods} has to be paid in accordance with the regulation of the given country. Some countries exempts  matured  crypto ^{i.e. crypto which is in users wallets for the long period of time} while others don't allow any exemption. The attempt to hide your crypto-profit from taxation may result in the penalty, jailing including, similar to early BTC investor who was " jailed for unreported crypto gains in $4M BTC sale".