Hi.
i didn't traded so much of my crypto for FIAT so i didn't dealt with that question yet.
however i think it's an issue need to be dealt with.
1. do you use accounting services?
2.if so, do you keep documentation of all traded or bought coins?
3. what do you do in cases of profit from ICO's
WHAT SHOULD I DO??
First you should have mentioned from which country you come from. And only from there people can help you with particular suggestions.
I come from EU and still, every Eu country has their own regulation regarding taxes.
I was thinking that i could pay the minimal amount needed to be legit (a particular type of bussines), the minimal amount is 15%. But I do not make enough to think of it right now.