A supermarket mega-giant could be forced to compensate customers ripped-off by a technical glitch.
About 70 North Island Foodstuff stores accidentally overcharged people for some groceries meant to be on special yesterday.
A Commerce Commission spokesperson says shoppers should be able to trust the price on the shelf, is what they will be charged at checkout.
They say if a mistake is made, businesses should ensure consumers are compensated and take immediate steps to prevent it from happening again.
Consumer Law expert Nikki Pender told Heather du Plessis-Allan the mistake could breach the Fair Trading Act.
"Advertising a product at one price, and then charging more at the till usually tends to be a bog-standard breach of the Fair Trading Act."