There is no Tax and there never be any Tax on Bitcoin. PERIOD.
One of Bitcoin famous rule is this:
No One can Tax Bitcoin
You will need to pay a tax, when you exchange your Bitcoin for U.S. currency or any other paper currencies in other countries.
In other words, the tax you pay is not from Bitcoin, but from using their paper currency. The Illuminati reserves the right to collect their tax on their paper currency.
This is how they're treating it in the UK and I like it this way as I'll just keep my coins as they are and spend them when I can.