If you’re moving to Idaho, put this on your to-do list: If you’re planning to buy a car pre-move, do it more than 90 days before you hit the state line. Explanation in a moment.

House Bill 359 is, in itself, not especially noteworthy. It comes from the state Tax Commission – ordinarily the source of a number of bills during the legislative session. This one, its statement of purpose says, would “allow non-resident students, temporarily residing in Idaho, an exemption from use tax for vehicles registered in their home state.”

Noted here not because there’s anything wrong with that, but because few such out of state students probably would have thought of owing the use tax on their car to begin with. The use tax, which most sales tax states have on their books, is an obscure cousin tax meant to levy taxes on things the sales tax doesn’t get. Live in Nampa and troop over the state line to Ontario to buy a household appliance or even a magazine in hopes of avoiding the sales tax in Idaho? Sorry, you’re now on the hook (legally at least) for the use tax. Not that the number of honest use tax payees in Idaho (or elsewhere) is necessarily all that large. (As former Idahoans, we’ll take the 5th.)

If you bring a car into the state, though, there’s another consideration. Presuming you’re going to stay in the state long enough to establish residency, you have to register your car. Suppose you bought it in another state? That fact will be placed in front of registration officials as soon as you produce the title. Do you owe the state a 6% ding?

The answer is, maybe. The Tax Commission points to state law (it’s in Idaho Code 63-3621) in drawing the bright line. If you bought the car more than 90 days before moving to Idaho, it’s presumed to be personal property, not purchased basically for use in Idaho, and exempt from the use tax. If you bought it within 90 days before coming to Idaho, you probably owe the tax.

A point maybe specially relevant to incoming college students.