system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do places like Costco and Walmart mark your receipt at the door before to leave?

Always confused me, and I don't see a logical purpose behind it.
gpt
Guessing, but it's to make sure you can't come back in, collect the same goods as are on your receipt and leave with them a second time. If you try to leave with goods and a marked receipt, they know you're trying to steal them.