again, depends what country you're in. in the US for instance you're expected to pay capital gains tax on profits realised. so if you paid alot less than what you sell them for you're expected to declare that profit and pay the tax on it. they also seem to want you to pay tax when you spend it as well if you paid less for it but i've no idea how that would work and i wouldn't bother mentioning it. 

the fees are to the bitcoin network. no tax there.