I wrote an app to calculate PokerStars and Full Tilt Poker taxes:
POKIRSCAN poker tax app | Download POKIRSCAN poker tax app software for free at SourceForge.net

It works from the Stars audit file or the FTP hand history dir or the new hand history request files available from the web (that's in private beta last check).

It computes gross winnings/losses which you need to report on tax returns (at least amateurs do). It nets out games if they're in the same session to lower the gross winnings which reduces tax burden. Games are in the same session if they're of the same stake/buyin/format and occur within the user specified amount of idle time.

Let me know what you think.