Presently, it is a US-focused federal capital gains/losses tax calculator for your bitcoin transactions.  The website provides you with your optimized trading activity for the purposes of reporting to the IRS, but this information is equally applicable to any state/city filing requirements.  That being said, there is an option to display 'RAW' transactions and their associated fair-market values that could conceivably be used for any country/jurisdiction filing requirements.  If enough interest is generated, we may expand to cover other countries.