If you want to avoid paying taxes on crypto, then there are both legal and illegal methods to do that. If you want to go the legal way, then I'd ask you to hire a good tax consultant. If you want to take the illegal way, then you can do that through pre-paid debit cards or cash on mail.
Instead of avoiding the taxes better pay the amounts which you got the profit because in future you might face legal issues with the government. Many people are doing such things because they don't want to pay the taxes but you pay taxes on time through cryptos you won't face any problems.
Actually, it depends on each countries as it will be implemented or not. Basically our government will able to support the crypto currency or not as it will be legalized on the particular country that we have. Here in my place our government supports crypto currency as we are able to provide a government issue ID just be recognized by our government and will able to do such different transaction by using a bitcoin.
I agree with nethan1btc, and I think how the government knows that their citizen using crypto or not unless they monitor all of their citizen's bank account and ask privately for each people to know more from where their income source.
in my country, we don't have to send any document to explain that we are crypto user and we can withdraw our bitcoin to fiat and send it to the bank account. but so far, me and my friends, using the third party to send the money to our bank account.