it won't work because that means taxing bitcoin twice! that is why tax laws in countries such as Japan are like this. there is a tax when you "invest in bitcoin" which i believe is like capital gains (but not sure) so you are paying a tax for bitcoin once here. then if the country recognizes bitcoin as a legal way of payment or a currency they can not tax it again when you make a payment with bitcoin because you have already paid your taxes on your bitcoins so the taxes here will be 0.