To make a purchase at a brick-and-mortar retailer, you typically insert the credit card into a card reader so it can read the security chip on the card. You may also be asked to enter your billing ZIP code. At an online retailer, you’ll be asked to enter the card number, expiration date, security code (typically found on the back of the card), and your name and billing address.
When you swipe your credit card to make a purchase, the merchant’s credit card terminal asks your credit card issuer whether the card is valid and has enough available credit.
Your credit card issuer then sends back a message stating whether the transaction is approved or declined. If it’s approved, you’re good to go. If not, you may have hit your credit card limit or your card may have been deactivated due to suspected fraudulent activity.
This doesn’t necessarily mean your identity has been stolen; card issuers may deactivate your card and get in touch if you’ve made unusual purchases.
For example, if you travel abroad, your card issuer may deactivate your card until it confirms that you’re the one who made the purchases.