Pak'n Save has apologised for mispricing its products, which lead to customers being overcharged.
Doug Cochrane, a spokesman for Pak'n Save owners Foodstuffs, said staff at Pak'n Save Kaitaia had been changing prices while the supermarket was still open on Sunday ahead of specials only taking effect the next day, according to Fairfax.
This lead to customers being overcharged.
Foodstuffs admitted the actions were not good enough, according to Fairfax.
"Changing tickets prior to the start of a promotional cycle is not acceptable and is not consistent with pricing integrity policies. I would like to apologise unreservedly to our customers in Kaitaia who while they were charged the correct price may have been misled by incorrect shelf pricing," Cochrane said.
Customers are able to bring receipts into the store for a refund.
Pak'n Save said it was investigating if the same mistakes had been made elsewhere.