A minor nit - it's not a sales tax that is due on out of state purchases, but rather a use tax (though it's commonly the same rate as the local sales tax). The

A minor nit - it's not a sales tax that is due on out of state purchases, but rather a use tax (though it's commonly the same rate as the local sales tax). The issue isn't so much that it's rarely collected, but that purchasers who have a legal responsibility to declare and pay it rarely do because there is (as you stated) no practical way for the state to track such purchases, excepting some obvious exceptions like out-of-state purchased vehicles - many states collect the use tax before they allow the vehicle to be registered. http://en.wikipedia.org/wiki/Use_tax http://en.wikipedia.org/wiki/Use_tax