You know the drill. After paying for your three-month supply of granola bars and a decade’s worth of sandwich bags, a Costco employee will ask for your receipt. She’ll glance in your cart and — I always assumed — confirm those 90 cans of Sprite were bought and paid for. But there’s more going on here than simple theft prevention.

In fact, it might just be in your head that the trusty receipt checker thinks you’re trying to embezzle your bulk items. According to Coscto’s customer service site, there are two reasons that they’re actually checking your receipt each time you exit the store (and these reasons have everything to do with keeping tabs on cashier performance and surprisingly nothing to do with the notion that you’re a shoplifter).

The first reason Costco checks your receipt is as a means of inventory control. Basically, by checking your receipt, Costco is ensuring that their cashiers correctly scanned each item in your cart. The second reason that the receipt-checkers exist is to make sure that you’ve been charged properly for the items you’ve purchased.

Cart history

“To my mind [the receipt checking is] really not just to stop people from stealing,” David, a former Costco employee, told Consumerist. “I hardly ever saw people that had items that had not been paid for. Literally maybe once or twice in a month of working the door. We would catch hundreds of dollars a week in overcharges, though.”

According to David, there were multiple instances during his time working at Costco that customers would accidentally get charged twice for items in their cart. In that case, a supervisor would either refund the customer’s money, or send someone out onto the floor to retrieve the correct amount of the overcharged item to add to your cart.

“With the kind of volume Costco does errors are frequent and sometimes just can’t be helped. The scanners are so sensitive that it’s really easy to accidentally scan something twice and not notice,” he went on to explain. “During the time I spent receipt checking I probably caught well over $1000 in overcharges.”

Still, even with the knowledge that Costco’s receipt-checking motives have next-to-nothing to do with customer mistrust, some people still get pretty heated by the policy. According to CheatSheet, an Oregon man took things to the next level when he got into a fight with a Costco employee after trying to sneak out of the store without showing his receipt. Wells ended up breaking his leg and suing Costco for $610,000—a jury awarded him nothing.

I think the moral of the story here is that if you’re a diehard Costco enthusiast (and, honestly, who isn’t?), try not to take their receipt-checking policy too personally. No, they don’t think you’re a thief—it turns out they truly do have your best interests at heart.

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