What are the specific card payment regulations that a merchant operating in the UK must follow?

RC: The PCI DSS Compliance Standards are the key ones in respect of card payments and are enforced by the card brands (Visa, Mastercard, etc.). Separately, there are other regulations that apply to merchant payments. Namely, the Payment Services Regulations include the Second Payment Services Directive (which is just about to be published and will be in force in two years’ time), the Merchant Interchange Fee Regulations, data protection regulations, the Fourth Anti-Money Laundering (AML) Regulations and Distance Selling Regulations (if they are an e-merchant or selling by phone).