if your country have impose tax on bitcoin then you have to pay tax otherwise there is no tax on bitcoin only those countries may be collecting tax on bitcoin who are already accepted bitcoin as legal currency.
Keep in mind that the government has taken a firm stance in the Bitcoin arena and they may try to do any number of things to make it hard on people until it all settles down. You start dealing with taxes on the trade of BTC and you might find other authorities knocking on your door with claims of money laundering.