A systems fault left Asda stores across the UK unable to accept card payments, leading to enormous queues at many shops.
Without the ability to pay by card, customers were forced to wait to withdraw money from cash machines or give up on their shopping expeditions entirely.
Shoppers took to social media to complain about the delays, with one comparing their situation to that of "cattle".
By the early afternoon, Asda had tweeted that most of its shops were back up and running but complaints continued to pour in.
Becky White had an extra 45 minutes added to her shop in Norwich because of the broken system.
"The doors are shut and people are shouting outside," she told the BBC. "The car park is rammed."
A spokeswoman for Asda said: "We are in the process of resolving a technical issue with our card payment system in stores.
"We're continuing to process payments as quickly as we can but we apologise to our customers for the inconvenience this has caused."
Some of the disgruntled shoppers vented their fury on Twitter:
Some Asda stores resorted to non-digital technology, digging out credit card imprinters from the back office:
But some customers were mollified by the offer of free chocolate: