I received this email from my Mother - she received the original from a friend, but having had it happen to my Mom, I thought it more than valid enough to post to as many people as I could reach. Mom attached the scanned copy of her grocery receipt showing the additional $10 cash back charge that she had not punched in and had not asked for. I'll see if I can figure out a way to attach it here;
BEWARE.
To all my friends:
You might want to read the email I received from a friend (below) first. Because I am very leery about passing this sort of thing on (in case it is done by someone mad at Walmart) I checked it on Snopes. See this link: Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

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What I found there made me feel that there was a strong possibility that a mistake was made either by the cashier or by the debit card holder and so I did not pass it on at the time. The Snopes article goes on to say that the cashier does not have the capability to put in a cash back amount which further made me believe that it was likely some sort of accidental transaction.
Today, I changed my mind due to firsthand experience. (By the way, thanks Bev, for the heads up, I probably wouldn’t have noticed had it not been for that recent article)
I stopped at Sobeys to pick up a few groceries on my way home and the total (stated by the cashier and visually checked by me) came to $116.43. When I went to complete the transaction on the machine, the total came to $126.43. I asked why it was different and the cashier said she didn’t know and became a bit flustered. I also looked at the cash register screen again and noted that $10 in change was due. (I can’t ever recall checking the register screen after completing the transaction and seeing the approved screen. – I certainly will from now on. ) At that point the transaction was completed and approved but I hadn’t yet got the tape and so I asked for it. There on the tape was the $10 cashback. I NEVER SAW a cash back screen on the unit, nor did I request cash back verbally and said so to the cashier. The woman called the supervisor over and they were going to reverse the tape. I said never mind, just give me the $10 change but I made it quite clear to the supervisor that I had not seen a cash back screen and had not requested it. The supervisor said the cashier must have caught the key in error and that it happens quite often. I found that odd, because if you do request cash back it is a two stage process, you have to answer the question first with a Yes followed by punching in the amount requested. It also makes a question of the comment in the Snopes article that the cashier does not have that capability.
I would like to believe it was a genuine accident, I have a strong loyalty to Sobeys and I like and trust the store. Unfortunately, given the requirements of cash back, I’m finding it a bit hard to swallow. However, I lost no money, so have no cause for complaint.
I just wanted to pass this on so everyone makes a habit of checking both the cash register screen, the amount, the small debit completion screen and then be sure to check the tape before leaving the area. I have included a scanned copy of the tape (it’s folded in the middle to fit on the screen – besides, I don’t suppose anyone wants to read my grocery list). The tape clearly shows the cash back and change due. Although I have very rarely taken cash back you can be sure I would never ask for just $10.
Jackie
Subject: Fw: Check your Wal-Mart Receipt
Another beware if using credit or debit cards!! Guess we’d all better stick to using cash.
THIS IS TRUE! It happened to me at Wal-Mart (Supercenter Store #1279, 10411 N Freeway 45, Houston, TX 77037) a month ago. I bought a bunch of stuff, over $150, & I glanced at my receipt as the cashier was handing me the bags. I saw a cash-back of $40. I told her I didn't request a cash back & to delete it. She said I'd have to take the $40 because she couldn't delete it. I told her to call a supervisor. Supervisor came & said I'd have to take it. I said NO! Taking the $40 would be a cash advance against my Discover & I wasn't paying interest on a cash advance!!!!! If they couldn't delete it then they would have to delete the whole order. So the supervisor had the cashier delete the whole order & re-scan everything! The second time I looked at the electronic pad before I signed & a cash-back of $20 popped up. At that point I told the cashier & she deleted it. The total came out right. The cashier agreed that the electronic pad must be defective. Obviously the cashier knew the electronic pad was defective because she NEVER offered me the $40 at the beginning. Can you imagine how many people went through before me & at the end of her shift how much money she pocketed?
This could probably happen at any store where they will give you cash back so be cautious.
Just to alert everyone. My co worker went to Milford DE Walmart last week. She had her items rung up by the cashier. The cashier hurried her along and didn't give her a receipt. She asked the cashier for a receipt and the cashier was annoyed and gave it to her. My co worker didn't look at her receipt until later that night. The receipt showed that she asked for $20 cash back. SHE DID NOT ASK FOR CASH BACK. My co worker called Walmart who investigated but could not see the cashier pocket the money. She then called her niece who works for the bank and her niece told her this. There is a scam going on. The cashier will ask for cash back and hand it to her friend who is the next person in line. Please, Please, please check your receipts right away when using debit cards. The store has the cashier under investigation now. We can only pray that she is caught very soon.
I am adding to this. My husband and I were in WalMart North Salisbury and paying with credit card when my husband went to sign the credit card signer he just happen to notice there was a $20 cash back added. He told the cashier that he did not ask nor want cash back and she said this machine has been messing up and she canceled it. We really didn't think anything of it until we read this email. Please be aware