Giving your phone number at a store checkout may seem harmless, especially when you’re offered a discount, loyalty points, or a faster checkout. But that simple number can allow a retailer to connect your purchases over time and build a profile of your shopping habits.

When a cashier asks, “Do you have a phone number with us?” the answer can do more than identify your loyalty account. It may help the store record what you buy, how often you shop, and which products or promotions interest you. Retailers can use this information to personalize offers, improve loyalty programs, and better understand their customers.

Your information may also be used for marketing. Depending on the company’s privacy policy, shopping data could be used to send targeted promotions or shared with affiliated businesses. This is why you may sometimes see advertisements connected to products you recently purchased or viewed. Practices differ from one retailer to another, so checking the privacy policy can show you how your information is handled.

There is also a security concern. Once personal information is stored in a company’s database, it could potentially be exposed during a data breach or other security incident. Even businesses with strong security systems cannot completely eliminate this risk.

The good news is that giving your number is often optional unless it is needed for something specific, such as order updates or account verification. Before sharing it, simply ask whether it is necessary. As the original article puts it, “Small choices like these help you manage your digital footprint.” Being selective about the information you provide can give you more control over your privacy without giving up every convenience.