Mo. Rev. Stat. § 238.280
238.280 Posting of increase in sales tax, when.
238.280. Posting of increase in sales tax, when. — In each transportation development district in which a sales tax has been imposed or increased under section 238.235 , every retailer shall prominently display the rate of the sales tax imposed or increased at the cash register area.
(L. 2007 S.B. 22 § 4)