Even if you received the BTC for goods and services, and then held them for 5 years and they 20x in value... you still owe capital gains. It's like saying: 5 years ago I sold goods and services for $100, bought stocks with the $100 and now that stock is worth $2000. When you sell the stock, you pay capital gains on $1900; you also should've reported that $100 in revenue from 5 years ago.
As for anonymity... you lose it when you associate a bank account to get liquidity (as mentioned by GP: "nominate a bank account"). Of course, this assumes you can't get liquidity in some other way... but that's non-trivial with large qty of BTC.
> Yes, that's true, but that not enough to enforce the tax code.
Uh, yes it is. Money came into your bank account, and you'll need to explain its origin if the IRS audits you.
Do you honestly believe the IRS would just give up on enforcing the law because you used a tumbler before you converted the bitcoins to USD and put the money in your bank account? The fact that you have the money in your account at the end of that process is what really matters.
In Canada I believe (don't own any bitcoin) you can withdraw from a few dedicated bitcoin ATM's, as far as I know you don't need to also use a regular bank ATM card in the process.
A good chunk of tax law is unenforceable if the evader is really clever. That's like observing you can murder someone and get away with it if you leave no evidence. But it's a big risk. You wanna risk jail to keep 15-18% extra? I know I don't.
As for anonymity... you lose it when you associate a bank account to get liquidity (as mentioned by GP: "nominate a bank account"). Of course, this assumes you can't get liquidity in some other way... but that's non-trivial with large qty of BTC.