Not sure about the UK, but in the US, don't retailers/FF places and all other establishments have to give a receipt if the person uses either a debit or credit card??? If so, lots of people use that form of payment in the US, so I would think that in itself would make it more difficult to figure out who the shopper is. Now....when the guideline calls for paying in cash, and the shopper has to ask for a receipt, well then I agree...maybe that gives the shopper away just a bit, and as wales posted above, it would be good for everyone to ask for a receipt all the time, so as to make it more difficult to figure out who the shopper is.