many country not yet make legalization of bitcoin and not make statement about bitcoin is it legal or not so i think your friend don't have to pay anything since bitcoin itself has free from tax. and i think better your friend move the bitcoin into another wallet like trezor or bitcoin wallet for pc to keep the bitcoin.
most of the countries has not yet legalize bitcoin, even they have no statement about bitcoin that either it is legal currency or illegal, and that is the reason that still people are using it freely having no restriction on it.