From what I understand, Bitcoin miners are charged income tax on the price Bitcoin is at the time the coin is mined, and capital gain on the loss or increase of that coin. For example, I mine one Bitcoin at $200, sell it at $600 – I get taxed self-employment income tax on the $200 and capital gains for the $400 increase.

However, I stopped mining Bitcoins a while before the guidelines were officially created by the IRS, back when Bitcoin was <$50 each. That said, I have no recollection or records of the pools I used to mine Bitcoin and I’m pretty sure the majority of them are out of commission by this point. I've also had to recreate my Bitcoin wallet several times along the way do to re-installing the OS/wallet getting corrupt. On top of that, the majority of Bitcoin now in my possession came from investing a few Bitcoins into other coins such as NXT that grew in price such that I was able to convert it back into several times the amount of Bitcoin I had put in.

My problem is, I’ve converted and withdrawn ~$20,000 worth of Bitcoin into my bank account. From my comments above, and now that Bitcoin is over $400 apiece, you can see most of my gains are capital gains from investing rather than mining. However, I have no record of my mining history, nor my gains history (the new coins I mainly invested in were newly created coins, aka I invested in it before it was officially offered on an exchange). When I file my taxes this year, would it be safe for me to file the $20,000 as $20,000 worth of capital gains (i.e. file everything I convert/withdraw for the full amount as capital gains) as opposed to worrying about the income tax portion?

I tried explaining it to the person I do tax with, but she couldn't understand that Bitcoin wasn't a third party and kept thinking there was a capital gains/loss form that I was supposed to get from some Bitcoin corporation (which there isn't).

I appreciate the help.