Registering a new car in Montana has a loophole that allows owners to avoid paying sales tax. The state has the highest number of registered cars per person in the United States.

Many luxury car owners register their vehicles in Montana because the state doesn't charge personal sales tax or require emissions tests on vehicles.

Basically, the Utah law says if you or your Montana LLC buys a car that is mostly used and resides in Utah, the sales tax should be paid in Utah and it should be registered here, too.

So, yes, you probably need a car to cross those vast open spaces—but Montana weirdly has the highest car ownership by population in the United States, more than double that of car-crazed California.

Montana isn't a state you'd associate with ultra-expensive cars, but more and more luxury vehicles are sporting Montana license plates these days. Here's why.