I personally haven't paid any tax over my Bitcoin gains, but that's mainly due to the fact that I barely actually cash out fiat to my bank account. That directly makes me wonder what the exact point is that I am supposed to pay tax. Is it (1) once I have sold whatever number of coins, but the fiat is still in my exchange account, or is it (2) once the fiat hits my bank account? I am hinting towards the latter option, but the first option makes sense too.
It is obviously (1), because that is when you have realized your gains. The exchange account is no different from your bank account.
If you extend the logic a bit further, are taxes due at (3) when you withdraw the fiat from your bank account?
Are you talking from experience, or is it just what you
think? In essence, there is no real evidence of me having gained any profits if I don't actually withdraw the funds back to my bank account. If I just continue to keep the fiat in my exchange account, how would whatever government agency ever know that I at that point realized a gain at all? The only way would be to force the exchange in question to hand over my entire account/trade history. Banks on the other hand, are basically an extension of the government since incoming deposits above a certain range or monthly transfer volumes are reported to the authorities.
Being able to hide your gains because there is "no evidence" (for now) does not mean you do not owe the tax (according to the IRS rules). If they ever catch up with you, by for example getting the information from the exchange exactly as you stated, you will then owe the taxes, penalties and interest on all of your unreported gains.
At one point I had three law firms on retainer burning through about $250,000 of my money: a Bitcoin savvy federal felony criminal defense firm [in CA], a special federal civil asset forfeiture defense firm [in CO],
and a federal tax law firm specializing in Bitcoin tax law [in NY]. So from direct experience: you
owe the tax the second you convert your crypto to fiat and realize a gain over what the price was in fiat when you bought it. Normally you can wait until the end of the year to fill out your Schedule D and report all your gains (minus all your losses) and then pay all the tax at once.
But if you have a large underpayment of taxes for the year there will be penalties and interest charged because you did not pay the taxes on time throughout the year
when you realized the actual gain at the time you sold the crypto.