TokenTax connects to BTC Markets for easy crypto-currency trade tracking and tax filing.
In your BTC Markets account, go to Buy / Sell and click on Trade History (https://www.btcmarkets.net/trading/tradehistory).
Click on the Export to CSV button.
Upload your CSV file to TokenTax (https://tokentax.co/import/csv).
TokenTax does the hard work so you don’t have to.