Investigation of Family Dollar and Dollar General prompts lawmakers to double penalties for retailers that repeatedly charge more at checkout than prices listed on shelves

Utah lawmakers have voted to stiffen penalties on retailers who chronically overcharge customers.

The new state law, which takes effect on 6 May, was introduced in direct response to a Guardian investigation of pricing practices at two national chains, Dollar General and Family Dollar, according to an official who oversees the state’s price-accuracy inspections.