[tzs]

That tax is a "use" tax. It is basically for having/using things in the state that you didn't pay state sales tax on.

You don't have to tell the state why no sales tax was paid--maybe you bought it in another state but maybe you bought it at a garage sale or from someone on Craigslist or something like that that doesn't collect sales tax.

The use tax is only legal if it is complementary to the sales tax (which means that the total you pay cannot be more than the sales tax rate) so that if you did buy it out of state and paid sales tax in that state your state can only charge you the difference between what the sales tax would have been in state and what you paid to the other state.

That does mean that you will have to tell the state where you got it if you want to get the reduced use tax rate, but as a practical matter most people only pay use tax on items that they have to tell the state about anyway, such as cars, where they will be telling the state that information even if no use tax is owed.