Russian Federation

With each sale bitcoin will need to pay personal income tax at a rate of 13%.

That is, if you bought 30 thousand bitcoins and sold for 60 thousand, then the tax must be paid from 60 thousand and so on with each sale.
Moreover, if we assume the cost of bitcoin has fallen, and you bought for 60 thousand, you sell for 30 thousand, then with 30 thousand you will also have to pay personal income tax.

The need to pay taxes in such amounts is due to the uncertain nature of bitcoin (whether it is money, or the right of claim, such as shares).

The lawyer also noted that frequent deals with bitcoin will signal to the state that you are doing business. By law, this must be done only after registration as an individual entrepreneur, otherwise article 171 of the criminal code "Illegal business"