Major retailers across the UK, including Tesco, Asda, Sainsbury's, Marks & Spencer, and McDonald's, are experiencing widespread issues with card payments on July 11. Customers are reporting problems with Visa and Mastercard transactions, forcing many to use cash. The technical issue has been confirmed by Visa, which is currently investigating the matter. Downdetector has noted a surge in reports of payment issues. The disruption has led to significant inconvenience for shoppers, with some being turned away from supermarkets. Tesco has specifically warned shoppers planning to shop in Express stores this weekend.