Yes bitcoin has a tax everytime you are going to make an transcation using pear to pear or person to person as you can see every time you are going to send bitcoin the tax are input in the transaction details or every time you are going to withdraw your money or exchange it into fiat currency. Hoping that goverment will not impose taxes soon.
Bitcoin is non taxable digital currency, maybe what you mean was the transaction fee. Transaction fee is needed for the transfer of funds so that the provider of wallet can also have profit, but thats not a tax, bitcoins are not controlled by government so they cant put some tax on every transactions, but once bitcoins have been legalized, tax will surely impose.