Paying taxes depends on which country you are purchasing Bitcoin in. In the United States, Bitcoin is considered a property, so you're legally obligated to report your bitcoin as a property investment, and pay capital gains taxes on it if the value appreciates.

If you're talking about an exchange tax, most exchanges take a small (usually very small) percentage of the overall value of the transaction when making an exchange.

If you're asking about general taxes, it might help to know which country you're from before you'll find the answer you're looking for.