How to catch a double charge at Costco, Walmart or Sam's Club before you leave

Why it's easy to miss at warehouse stores

A big cart means a long receipt, and a long receipt is hard to read at the register while the next person is unloading. Bulk packs are heavy and awkward, so an item that doesn't scan cleanly the first time sometimes gets scanned again, and both scans count. At self-checkout you can do it yourself without noticing. How double scans happen.

Start with the item count

Costco and Walmart both print an item count near the bottom of the receipt. Costco's door checker uses that number to compare against your cart, and you can do the same before you get there. If the receipt says more items than you're taking home, something was rung up twice.

The count isn't perfect. Items sold by quantity or weight, and some fee lines, can be counted differently from the lines you see, so treat a mismatch as a reason to look closer, not proof of a mistake.

Costco

• Look for repeated item numbers. Each line starts with an item number. The same number on two lines with the same price is the thing to check.
• Don't mistake a discount for a duplicate. An instant savings line repeats the item number with a slash and shows a minus amount. That's money off, not a second charge.
• Don't rely on the door check. It's mainly there to confirm everything in your cart was rung up. Checking for an item you paid for twice is up to you.
• Lost the paper receipt? In-warehouse receipts show up in the Costco app and on costco.com under Orders & Purchases. New purchases can take up to 24 hours to appear.

Walmart

• Check "# ITEMS SOLD" near the bottom of the receipt against your bags.
• At self-checkout, read the screen before you pay. If something scanned twice, an attendant can remove the extra line. That's quicker than fixing it after you've paid.
• Already paid? Take the receipt to customer service before you leave and point out the repeated line.

Sam's Club

• Using Scan & Go? Your cart in the app is the receipt. Open it and check quantities before you tap pay. An item scanned twice shows up as a quantity of 2.
• At a register, read the quantity on each line. Sam's Club prints a repeated item as one line with a quantity of 2 or more, not as two separate lines, so a double scan won't jump out as a repeated line. Any quantity you didn't mean to buy is the thing to check.
• If you've already paid, the staff at the exit or the member services desk can help correct it.

If you find a double charge

1. Fix it before you leave. Show the receipt at the registers or the service desk. A double scan is a routine fix, and the refund goes back to your card.
2. Already home? Take a photo of the receipt, because thermal paper fades, then call or go back to the store.
3. If the store won't fix it, dispute the extra charge in your banking app or by calling the number on the back of your card. How to dispute a double charge.

For a quick routine that works at any store, see the 30-second receipt checklist.

Dupe Detective reads Costco and Walmart receipts line by line. Scan the receipt before you leave and it highlights any item that appears more than once, so a double charge gets fixed at the counter instead of on a call to your bank.