As far as I know, apparently you need to know what the price of Bitcoin was on every single trade you ever did... I think this is simply insane. Who knows what the hell one did during Mt Gox, Mintpal etc? all those exchanges are dead, so unless you didn't write down every single trade you lost this information. What to do then?
This is precisely the problem that BitcoinFastTax.com (BFT) solves. It has every bitcoin trade in the blockchain matched with the then mark-to-market (MTM) value. So for someone to get all this trade information for their IRS Form 8949, they simply enter their addresses in the BFT calculator page and the calculator does the rest, producing all trades and MTMs in a downloadable grid. The user can choose various optimizations too, such as FIFO, FILO, Average, etc. BFT can retroactively produce data back to the beginning of bitcoins (2009).