They cannot tax it because they do not know to whom will they give the tax. It will only be taxed if the cryptocurrency market is decentralized.

I think that Bitcoin is not taxable that is not because of anything else because of bitcoin is running on decentralized network .So, any government cannot controlled the bitcoin’s taxes. If bitcoin can be controlled by centralized authority in future then bitcoin will be taxable.

It is possible.. under certain conditions.

For example, in most European countries, the government determines the amount of taxaton due by the individuals according to their banking records. Well, in reality, they ask the employer to state the wage of all employees, then they ask each employee to state their wage (and other resources as well) and with these, they determine the amount to take.

Yet, in some cases, divergences appear between all the statements. Therefore, in such cases, the State can ask the bank to see the record of all transactions. In such a situation, if someone has changed bitcoin for euros and put it on their bank account, it will appear as a resource. And thus, will be submitted to taxation.

But indeed, this case is very specific. And I guess most of the time, gain from bitcoin are just hidden by inidividuals and ignored by governments. Just because for the moment it will be more costly to try to find those owning bitcoin than the gain the State would make with the taxation of such operations.

As you guys, I am not an expert. Maybe there is already a dedicated branch for that but... I bet there isn't!

Specifically bitcoin, no. However, capital gains tax for sure. I don't know how it works outside the UK, but you have to declare when you make profits on interest/investment over I think it's 11k. If you don't you'll be in trouble if they find out...which they probably will if you're withdrawing a lump sum greater than that.

That tax here would be 28%. There are ways to get this lower though, but you'll probably need an accountant for that. Feel free to drop me a PM if anyone in the UK needs one - I can get good rates with a friend of mine.

With bitcoin it is impossible.
But how are you going out?
It is still cash or fiat.
When you go out that could be the way to put a fee on you plus questions where you got the money.
If they cannot track you within then they will be waiting at the other end.
That is possible.

I don't really understand programming as well, and i don't know if there's a way to detect all of our transaction using bitcoin.
But if yes, it'll be possible that we will be taxed for our bitcoin income, since it's an income anyway, so we need to pay tax as a citizen.
But unfortunately, i think it'll be hard to detect and track our transact history, when and how much we sell our bitcoin, how many income we get fom this and such.
So it'll be hard to do so, but maybe in the future it will happen with technology development, who knows?

oh definitely it is happening. IRS has requested exchanges to hand out the customer lists together with their transactions. So USA has it covered. And then there is this joint France and Germany proposal to regulate bitcoin (read: regulate bitcoin taxation) that is going to be raised in next G20 summit.

So I think that it is happening all over the world and it is not the question of cooperation of exchanges with governments, as some other member suggested. Rather, it will be passed as a regulation, meaning that exchanges will be obliged to pass certain information to IRS and other tax institutions.

It will be impossible to force every one to pay taxes. Millions of transactions are generated every day and knowing their sources is not an easy task since it can be created from an exchange that does not require ID verification, besides the use of VPSs and proxies makes it harder.
The easiest way is to control exchanges and make them pay taxes, in return they will ask their users to pay more fees.

In my country, i know in due time our government will find a way  how to tax income from bitcoin. Our government is so desperate in taxing businesses and individuals. My government is so good at finding ways to tax its people in fact recently it passed a tax law which the government claimed to be pro poor but in reality its otherwise that people from all walks of life middle earners and low earners are both feeling the bad effects of that tax law. So it is possible that bitcoins will be taxed here in my country.