Taxing currency is an absurd thing because I've only heard about taxing goods before.
If the tax on $1, what would be the value of $1? This is illogical so it shouldn't happen. We have a burn-in every transaction for every altcoin. Bitcoin doesn't have that mechanism, just the transaction cost and usually, it's very small. So I think that taxing cryptocurrencies can happen when they profit from trading. Taxing Bitcoin is the act of treating Bitcoin as a commodity, not a currency.