I think their are some country who have started taxation on bitcoin as they have accepted the bitcoin. but their are some country who are still in confusion in bitcoin technology and not given any detail on bitcoin. even bitcoin being decentralized if you want you can show the taxation as live trading in Shares and calculating the profit and submitting the tax. But be carefull as some country have declared bitcoin as illegal in that country you should not show anything about bitcoin in your accounting if not you will be in problem.
so each and every country have their own rules on bitcoin.