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??
I recommend you not to trade directly from FIAT to Crypto instead buy some BTC/ETH and trade it to crypto. In that you are far from the eyes of the regulators. Don't be a victim like coinbase trading that imposed a tax to every costumer and there you go, paying the unexpected tax.
You can act ahead of time to prevent this taxation to happen. The market right now is unregulated so everyone should enjoy the privilege of no tax policy.