Which payment system is widely used in the United Kingdom for point-of-sale transactions?

The payment system widely used in the United Kingdom for point-of-sale transactions is Electronic Funds Transfer at Point of Sale (EFTPOS). This system allows customers to make payments using their debit or credit cards directly at the merchant's location, facilitating immediate and convenient transactions. EFTPOS integrates with the payment networks to authorize and process payments in real time, which is critical for the fast-paced environment of retail settings.

In the context of your choices, other systems mentioned serve different purposes. For instance, the Electronic Funds Transfer Association is involved with standards and practices for electronic payments but is not a specific payment method used at points of sale. The Automated Clearing House (ACH) focuses on batch processing for transactions, such as direct deposits and bill payments, rather than immediate point-of-sale transactions. Electronic Financial Services encompasses a broad range of online financial service options but does not specifically refer to point-of-sale payment methods. Thus, EFTPOS is the most relevant and widely adopted system for in-person payments in the UK.