Giving your phone number at a store checkout often feels like a routine part of shopping. Many people share it automatically to receive discounts, earn loyalty points, or complete a purchase more quickly. It seems like a small detail, but that single piece of information can connect your shopping activity in ways many customers never consider.

When a cashier asks, “Do you have a phone number with us?” the answer can do more than identify your loyalty account. It can link your purchases over time, creating a record of your shopping habits. Understanding how this information is used can help you make more informed decisions about your personal privacy…