Your post is self-contradictory. Currencies can't be taxed. If Bitcoin is classified as a currency, then it can be taxed only at the source (i.e income tax). Only assets comes under capital gains tax. In a way, you earn no real profits from a currency, irrespective of whether it is a fiat currency that is not protected against inflation, or a cryptocurrency such as Bitcoin that is protected from inflation. Do you pay tax on your savings bank accounts? Suppose you are having $10,000 in your bank account, do you need to pay a monthly or yearly tax on this amount?