I was in our local Tesco Express a short time ago, buying some Penguin bars. They were on offer: Buy One, Get Two Free. (Yes, really.) Now, I'm partial to a Penguin and a Rocky Bar with a cup of tea in the afternoon at work - yes, one of each, thanks very much. I was fresh out of Penguins, so this evening's offer was too good to resist.
I p-p-picked up six packs, nine bars in each pack. The shelf price for a pack: £1.82. This makes each Penguin a fraction over 20p, about twice what I'm prepared to pay - hey, I'll be a (middle-age) pensioner next year! - but 27 Penguins for that amount makes each one less than 7p. Bargain.
At the self-service checkout I scanned the six packs. £1.82 came up with each beep. Clubcard scanned. Beep. Subtotal £10.92. So far, so expected. Six times £1.82 is £10.92, and I know that the discounts are applied when I press "Finish and pay".
I press. Total to pay: £3.50. Three pounds fifty? I mentally calculate how much it should be. Twice £1.82 is £3.64, so Tesco is undercharging me 14p! I can't see any catch, so I insert my tenner, collect the £6.50 change, and study the receipt.
There are six entries of £1.82, with a subtotal of £10.92. Fine so far. Then the Multibuy Savings section.
MCVITIES B1G2F .... -£7.42
Hang on, four times £1.82 is £7.28. This is where things seem to have gone wrong in the Tesco computer. How can a machine which makes thousands of calculations a day get a simple repeated addition wrong?
This time the error is in my favour, but how often does it work against the customer?
I think I'll visit tescocomments.com as invited to on the receipt and tell them. I don't suppose they'll ask me for the 14p back.