My wife paid by credit card in a small local shop.
She looked at the receipt when she got home and noticed that it said Merchant Copy and had the full credit card number, plus start and end date. I don't believe it had the security number from the back or, of course, her Pin number. She became alarmed (nothing new) and expected me to know whether the business could be trusted not to spend all her money using phone payments. She says the owner is a nice man.
It looks as though this may be fairly normal to allow businesses to make refunds, provided the receipts are held securely under lock and key and destroyed securely after a certain, unspecified, time.
Does anyone know whether the law in the UK is specific about holding the unencrypted, printed data locally, and whether there is any financial danger.