Per your question I assume you are US based.However the exchanges you are trading on are probably based all over the world, in various jurisdictions. If you want to declare your earnings on an asset:Declare and have transactional proof of the price you bought the asset at.Declare and have proof of the sales price at which you liquidated your holding at the asset.As long as you follow the spirit of the law and have evidence (in case of audit) you should be fine.These are uncharted waters, and trying to be above board is half your battle. I’m sure this fiscal year will have many more higher value and more interesting cases for the IRS to investigate.FYI I am not an accountant or lawyer, I also believe you could with some work, fill out a 1099 yourself to provide this information on your own behalf .