Amazon admitted that it might have overcharged its shoppers who opted for the self-checkout machines at 1,600 of its stores across the United States because of a technical issue.

Documents seen by Bloomberg said that the issue began on March 19. Aside from customers getting overcharged, there are also others who were undercharged for items across categories such as food and apparel. 

In March, some customers who recently used Walmart's self-checkout kiosks noticed that they have been charged abnormally high prices, and have since complained about it. 

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Walmart's Self-Checkout Machines Overcharging Customers

According to Walmart, the source of the malfunction was due to what they called an "internal system failure" that prevented updating price data at the kiosks, with its tech staff still sorting the issue two days after it began. 

The company also confirmed with Bloomberg that affected customers were overcharged an average of 1.88% of the total amount of items they were checking out at the machines. Since the issue, about 80% of the customers have already been reimbursed. 

Walmart has also claimed in April that it was removing its self-checkout lanes from select locations in Ohio, Montana, and New Mexico, replacing them with "traditional lanes," which is speculated to be checkout lanes manned by Walmart staff.

The Wall Street Journal first reported about the glitches at the time, saying that the outage was not unusual at retailers but has become less frequent among those that adopted technological innovations in the industry. 

Bloomberg also reported that Target and Dollar General have paid settlements to resolve their respective legal actions filed by government officials who accused the retailers of overcharging customers. 

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