At one point of view bitcoin is an instrument for investment so ppl buy it willing to get income in their currency.
At the other point it is a currency and it might be used with a purpose of saving. In this case the tax would be stupid.
Here in some countries bitcoin is regualated so people are using bitcoin with the pay of the tax smoothly but in those countries where bitcoin have no official approval to use or not to use is having a big confusion that why we should pay tax if no rule or law made by the government of the country and also why they are not decalres bitcoin as legal way of use Because they want tax .
Well here if in your country no rule made for the bitcoin then surely you should pay monthly with the option of the other category tax ( one of my friend paying tax much to use other category of the tax section