Supermarket self service - possible to scan twice?

[trillionnaireshortbread]

I bought 3 of the same food product from M&S, scanning each in turn. I checked my receipt when I got home, and the item was listed 5 times, meaning I was overcharged. I'm pretty sure I didn't scan any of them more than once. Even if I had, surely the system should recognise it as an error? It does in Tesco - you can't scan the same thing twice, not least because it won't let you scan another item until the first is put in the packing area. (M&S doesn't seem to weigh scanned items, so perhaps its not so fail-safe?)

Tesco allows you to scan items twice.

I buy 2 packs of pork pies, always accepted.

I think you’ve answered your own question. Worth pointing it out to M&S and see what they say.

@VeniVidiWeeWee You’ve missed the point!
Tesco won’t let you scan your 2 packs as 3 or 4 packs because it tells you to “ place items in the bagging area” before doing the next. Op has been charged for items she didn’t put in bagging area.

It is possible to do it in Tesco by accident (I have done so previously), especially if you have a lot on there. It probably bibbed through the extra times without you noticing, I would just contact them and explain and ask for a refund.

Of course you can - and you're quite right it's only a problem in M&S because there's no weighing. Can also be a problem with scan-as-you-shop systems. It's handy when I am buying 4 of something to be able to just wiggle one in front of the scanner until there are 4 on-screen. Chalk it up to experience and in future look at the screen before you pay, you can scroll through the list to check for any errors.

Yes - as pps have said, many of the self service tills in M&S don't weigh things so it's possible to double scan. Worth asking about a refund next time you're in.

I have done this accidentally in M&S but always noticed at the till and they just take it off.

I would give them a call.

I like the fact they do not weigh, it generally makes it a lot quicker, as no "scale errors" like other shops.

I'd take the receipt back and see if they trust you. It does come up on screen as you scan so this is your mistake, not theirs. Once it's scanned, you need to move it to the bagging area

The Co Op is the same .. no weighing

Easily done OP

That's happened to me. Also in M&S. Very annoying if you realise once you get home.