I don't know where you got this idea. In the US When you trade something or barter it is your responsibility to document the value of the trade in US Dollars and pay taxes as if you sold it for that amount and you can be audited to make sure your methods are valid.
People should keep in mind there are potential tax consequences when using Bitcoin. However, there are at least four reasonable approaches, not just bartar, that one can take. And record keeping is an important duty also. But Bitcoin is sufficiently flexible for a creative tax planner to work wonders.
Of course, all of this is covered in
A Lawyer's Take On Bitcoin And Taxes.