https://customerservice.costco.com/app/answers/answer_view/a_id/714/~/why-do-i-have-to-show-my-receipt-at-the-door%3F https://customerservice.costco.com/app/ans

https://customerservice.costco.com/app/answers/answer_view/a_id/714/~/why-do-i-have-to-show-my-receipt-at-the-door%3F https://customerservice.costco.com/app/answers/answer_view/a... Its also loss prevention.