Well it depends on the country, in most places bitcoin isn't regarded as currency so it's never paid to tax it
How's that? If Bitcoin is not a currency, you may still have to pay taxes on it. It can be considered as property or commodity, and then you will have to pay the property tax when you sell your bitcoins.
For now bitcoin is not taxed. However bitcoin and other crypto has a tx fee only.
If in the future bitcoin is considered as a legal asset, maybe it can be taxed.
In many areas you still have to pay income tax.