Credit card companies have an incentive to catch fraud quickly, as every unauthorized transaction has the potential to reduce their bottom line. Their efforts can save you the stress of an unexpectedly high bill that results in hours spent on the phone trying to get unauthorized charges removed from your account. However, they also can come as an unpleasant surprise if your legitimate use of the card draws the attention of the fraud department.

Shopping Habits

One pattern that draws the attention of the fraud department and helps it catch fraudulent activity is a small purchase followed almost immediately by a large one. Thieves often make a small purchase first, ideally one that doesn’t involve face-to-face contact with a cashier, to confirm that a stolen card is still active before buying a big-ticket item. Swiping the card at a gas station, followed quickly by the purchase of expensive electronics, would be one series of transactions that a fraud department might flag. Multiple purchases over a short timespan also draw attention, since that can indicate a desire to exhaust the credit limit quickly before the theft is noticed.

Customer Usage Patterns

Credit card companies track how customers use their cards, and deviations from your usual shopping pattern can signal fraud. For example, if you typically use your credit card only to buy gas and the company notices that the card has been used to buy $2,000 worth of jewelry, that’s probably going to draw the attention of the fraud department. If you’re a new customer, your purchases are compared to those made by similar demographic groups in your zip code to determine deviations from the norm that may indicate a compromised account.

Strange Locations

Sudden usage overseas or in a different geographic area than usual also can be an indicator of fraud. This is particularly true for usage in two areas in a short window of time. Many times this keeps a card used legitimately in Chicago from being fraudulently used in Paris. But if you share a card with your parents, your dad’s usage to pay the electric bill at home could cause your own transactions on your spring break trip to be denied.

Better Safe than Sorry

The aggressive nature of fraud detection systems can result in a legitimate customer having a purchase denied or an account suspended or canceled for no cause. Some credit card companies will try to alert you when it takes such actions, but you may not find out until your card is denied and you contact the issuer for an explanation. To prevent this, call your issuer in advance when you know you'll be using the card in a different way, such as before embarking on overseas travel.