...to resent having to doublecheck EVERYTHING?

I always check every receipt - just last week a £2.99 baby bath oil came up as £3.99 in Savers and nappy bags priced at 95p on the shelf ticket scanned as 99p each in Aldi. I always ask for the money back even if it's a few pence because it's the principle that annoys me, putting a cheaper price on the shelf ticket is a fraudulent practice at the end of the day.

Lily - yes, I'm the other person ostentatiously waving my £20 (or £10) saying loudly 'Sorry, I'm having to give you £20 (or £10)!' Especially in markets!
Yesterday in the Co-Op I bought a few things including a pack of yoghurts reduced from £3.99 to £2.99. At home as I was about to put the receipt into paper recycling I checked it, for once. I'd been charged the full price. The reason was obvious when I looked at the outer of the packing, the reduced sticker with barcode did not cover the original barcode. One more thing to check in the shop!

Another one who always checks receipts - was charged £20 for an orange in Sainsburys once - scanned as a bonsai tree!

When I give an assistant a £20 note I say loudly, 'Oh, sorry, I'm going to have to give you a twenty as I have nothing smaller.' Then you can't be fobbed off with change for a tenner. Many of my acquaintances have fallen for this as was I. Once.

I always check my receipts.... In fact I always write down the prices and roughly add them up as I shop so at the till I know more or less what the amount should be!!! Keeps my brain active as well!

Yes it is very strange that errors are always in the favour of the retailer and never the customer.

I was advised to make sure that the bar codes were facing the cashier rather than the scanner but things can still go wrong. I always sit and check my receipt before I leave - two weeks running they'd made a mistake in their favour.
It's damned annoying but worth checking and complaining politely.

Perhaps not in supermarkets but certainly elsewhere I know of undercharging.

Last year DD checked her till slip on the way home from a very nice meal out and found they had forgotten to charge for the pre meal drinks. She rang them up to offer to pay and they refused to take payment saying it was their mistake.

Many moons ago I bought some office chairs and other goods in Staples. I queried the bill at the till as it seemed too low. I thought I had only been charged for one chair. The till assistant was really quite rude to me for questioning him. When I got back to the car, loaded it up and sat and checked my bill. I was right. I had been undercharged. I drove away. I had noticed the undercharge in the shop, drawn their attention to it and they had seen me off, so I refused to go back

I'm surprised no-one seems to be aware of the upside to overcharging. We love it!

In Tesco you get 'Double The Difference'. So if overcharged £5, you get £10 back. Sometimes the refund is more than the whole bill - they pay us for our shop.

In Asda, they offer a £2 gift voucher. All a lot cheaper for them than a £10000 fine and £10m worth of bad publicity for the criminal offence of misleading price indication.

Always check. Like others on here we found out the hard way that bills arent always correct. Worst one was Barclays, who rang me up to tell me I was over £2,000 overdrawn. Turned out the cashier had put my little cheque through, then not closed the account and opened the next customer's account before putting the next cheque in. They 'forgot' to remove the bank charges they had charged me for being overdrawn but were puzzled why we moved banks the same day.

I got charged twice for a pizza delivery from Dominos. Web site said I had to talk to shop manager who told me it would be refunded within two weeks. Two weeks later spoke to shop manager again who now told me I had to ring Dominos HQ. Another two weeks and I finally got my refund.

Even online you can get diddled. I was shopping for perfume and a site I use often had a 20% discount so went ahead and entered discount code, completed the purchase and lo and behold the confirmation email showed the full price. I went back and cancelled the purchase.

Of course I've just realised, too late, that I could have bought the blessed icecream then donated it to someone at the check-out.

The £10 Dine-In's also one to watch because if you miss an item (eg, forget to choose a side when the offer is main, side, pudding and wine) the system charges the full amount instead of the £10. I had to forego my Dine-In deal the other week as they only had ice-cream left for the pudding option - I was on the bus so it'd have been dripping everywhere by the time I got home!

Recently I bought the £10 Dine-in at M&S plus a few other items, was about to pay and thought it seemed expensive so I questioned it. The apple pie I had chosen was the problem - it had a different bar code from the other apple pies in the cabinet so was not coming up as part of the £10 offer. Had I been paying for a larger 'shop' I probably wouldn't have noticed that I was paying full price for the pie.

Always check before I leave the shop after getting charged £9 for 4 mushrooms in Sainsburys!

Most of the reports above about errors should have been taken up immediately with the manager. Nothing less. Do not be fobbed off. Such errors demand an apology and in most cases manaagement would have offered some compensation.

I always do.

My treat every week is to go to our local coffee shop for a bacon sandwich and coffe and read the Guardian (no Mail in this shop). I know exactly how much it will be as I have only 2 pieces of bacon in the sandwich instead of 3 , so when I get told it's more I question it and explain why. Also when I was short changed by a £5 note and didn't realise straight away, when I went back and explained I thought they had short changed me as I couldn't remember spending any money anywhere else, they gave me the £5 and said they would check the till at night and if it was short they would let me know when I next came in.

A month ago, thinking my grocery bill was high, I checked my receipt to find I had been charged £11.34 for cheese priced at 1.34.
I then called and was told to ask for the duty manager by name and to go back to sort it out, but they were very helpful and apologetic, refunded the £11.34, and gave me a £5 voucher, also keeping the cheese!!
Then the next week I noticed that cereal I bought on offer at £2:50 had been charged at £3:45 the normal price. The girl couldn't deal with the maths of the price difference, so refunded the £2:50!

So I now check my receipts, everywhere I go.
I suppose it's the problem with technology, not infallible.

I always check my receipts now after finding many mistakes in the past. I check them before I leave the shop if I can and if not, I sit in the car park and check. I hate getting home and then having to go back again, so it's simpler for my with my method.

I never usually check, but as I'd read this is just queried the 'buy 2 for 3 pounds' deal I'd just got. My items had gone through at their normal price. About 70 odd pence difference.

I try to add my purchases up as I shop rounding them up to the nearest 50p or£1 so when I get to the till I have a good idea of the cost it's paid off a couple of times

We bought some plants in a garden centre last Friday and on the way back to the car my husband was checking the receipt because the total was about five pounds more than he had estimated. He found we had been charged for a mouse trap and was refunded the amount. We usually do a mental calculation for small purchases; it is not so easy for a big shop but one of us usually has a quick look at the receipt.

I always try to check my receipts if not at the till but always before I leave the store. I must be luckier than most as I rarely find I've been overcharged.

Funnily enough I'd been in the shop at our local garage the other day & found when I got 1 item hadn't been charged for !!! No I haven't been in to tell & I shop there regularly, don't think they will have noticed.

I have been lucky in M&S when buying clothes, couple of real bargains, till price far less than ticket price