I'm finding supermarkets locking their regular prices behind an app or loyalty card is getting out of control. Out of all the major supermarkets, ONLY Aldi has nothing of the sort currently.
Tesco and Sainsbury's will often have a £3 item that costs £6 without their loyalty card. Of course it's £3 in every other shop: it's not a special offer for members, it's a punishment price for those who don't give away their data.
Plenty of cash only businesses in the UK that engage in this, although of course just because a business is cash only, doesn't mean they're a tax dodge.
IMO the two things are separate: it should be the tax office that does audits to catch this. It's not very hard to see a vape shop that makes £500 a month with two top model BMWs outside might be dodgy.