Whether you are planning on paying taxes on your bitcoin-related trading gains or not, I figured it'd still be nice to know what they WERE! Or if they were gains at all.
Which is why I now added to Bitcoin Builder a "gain / loss analysis" section at:
https://www.bitcoinbuilder.com/taxes/You can upload your complete mtgox trading history (or use our own simple CSV file format for whatever trades you've made), and the site will automatically tell you what your realized and unrealized gains (or losses) are, as well as what portion of your realized gains are short-term vs. long term (broken down by calendar year). You can even choose a matching algorithm between FIFO, LIFO, Lowest Cost, Highest Cost, and "Tax Lot Optimizer" (match losses first, short term to long term, then do gains, long term to short term).
It will also automatically calculate your CAGR (compound annual growth rate) on your unrealized gains.
Enjoy! All the data is anonymous and you can wipe all records from our system at any time instantly with one click.