somebody is more then willing to pay tax. But should you not show HOW you made that amount of btc (the same with 10 million in cash, if they stop you on the road with ten million in cash they will put you in prison if you can not say where it came from)? authorities could think that somebody is a ransomware attacker or a darkweb criminal. The lawyer somebody spoke to said that you have to be able to show the source of your funds. He said something that criminal law says that you have to have proof for an offense. And that in tax law they can fine you on assumption. Somebody is confused and afraid.

 selling it part by part, that is not a good option because it will take a life time. and somebody does not believe that btc will be the one and only for the rest of our lives. As well, if you exchange bit by bit, and it is a million in a few year, and somebody has a 1500 euro salary, that might be a red flag for the bank. somebody has already loads of cash and prepaid credit cards. exchanging bit by bit does not allow you to invest either, you are not able to buy a house with it, not able to invest a million in a companies etc..

the question is: will authorities allow it, if somebody has millions suddenly out of nothing and  can not show where it came from. somebodys lawyer says he does not know what will happen and that he has to write the authorities which he is doing now.

Unfortunately that somebody does not have his old wallets/keys anymore. that somebody changed wallets many times and changed his btc into dash, and even mixed the coins. because that somebody believed in privacy :-(   after dash skyrocketed changed back his dash into btc and there is no way of proving where it all started. that somebody feels stupid, but at that time nobody expected crypto to go through the roof. it was a hobby.

If you can find an exchange that will accept to exchange into fiat, then the next problem will be your bank. The bank will close your bank account for sure(already happened to that somebody with to european bank accounts and one hong kong account). if you can not show source of funds to your bank, then you are fucked.
but suppose you would pass the first problem, that the bank will not close you, then you have the next problem: the tax investigator, and the public prosecutor, they will want to know where the money comes from. I do not know what they will say if you can not show where it comes from. It is the same if you suddenly have millions of cash in a suitcase. Where did it come from? you can say you found it, but it is not credible. and the same for 2000 BTC. if you can not show the origin, where you bought the BTC(which that somebody after all these years of trading can not show) then you have a potential problem.

anybody that has advice?

anyone tips:

there is somebody from europe.

supposedly somebody has 2000 BTC, bought in 2009. And after 2009 that somebody traded into alts back and forth into BTC many times. That somebody can not proof how and when he obtained the BTC.

How can you sell a part of the BTC and enjoy the money? If you exchange such an amount into FIAT all alarm bells ring and your money is blocked immediately. that somebody tried to sell a few 100 BTC, and opened an anonymous bank account in hong kong. The account was closed immediately. That somebody tried to sell some BTC through bitstamp. Bitstamp immediately blocked his account because he could not show where the BTC came from.
That somebody is also afraid that the police will target him as a criminal because he suddenly has millions, that somebody has a normal job and makes less then average salary.
that somebody also asked a lawyer and he said that it is risky because you can be accused of money laundering if you can not show how  you bought it and he never has seen a case like this so he could not really advice.

How can that somebody sell lets say 500 BTC? that somebody believes that BTC needs to deflate and wants to invest his money in technologies and not in crypto itself. anyone tips?

Please no discussion if this story is bullshit or not. Tips and advice only.