I don't think so. Not being taxable is the one of the thing I like about bitcoin. The government can't get to us, the bank can't to us. Everything here is done by user to user.
Bitcoin may not be taxable directly, but the profits earned with it definitely are. In most countries you will have to pay an income tax on such earnings. Whether they will be able to catch you for tax evasion if you don't pay this tax is another matter, but in the US you'd better not look that way. The IRS is no fun to play with.
But how to determine if there is a profit, or vice versa, what is the loss? Does a tax credit arise? In what size?
Well, the process is pretty easy and straightforward really, and it is the same as with stocks, for example. Let's assume that you buy 1 share of some company at $1,000 and then the price rises, so you sell it for $1,500. Your profit is thus $500, and this is the amount which you should calculate your income tax on after applying tax deductions if there is any.