Some states have no taxes. Contrast Washington (state) and Oregon. Oregon has no sales tax, but an income tax. Washington has sales tax, but no income tax.

In Portland (which is right on the Washington-Oregon border), I recall a car with the license plate "TAXFREE," which was ambiguous enough that I couldn't figure out if it was referring to the owner being "tax free" (paying no income tax living in Washington) or that the car was "tax free" (the owner paid no sales tax when purchasing it in Oregon).