Thanks
I don't know a single one. Im not convinced yet about cashing out a single satoshi. What if the accountants make a mess and you end up in trouble? because as far as I know, if the accountants make a mistake, you will be the responsible, not to them, I just don't trust accountants, don't even trust the taxmen to be frank, this is too new, there is nothing clear, I don't want to get my bitcoins counterfeited or stolen away from me in the process, it's not fair.
Where did you get the bitcoins from?
If you bought them in exchanges, you will need the receipts of each buy, all the trading history etc.
If you got paid in BTC for products or services, you will need to prove these are legal.
At least in some countries that's how it works.