The dark line on the back of your ATM card is a magnetic strip that contains identifying details about the card and its owner. Each time you swipe the card through an ATM or card reader, the machine checks the data from the stripe with a verification company before it completes the transaction. It's sometimes difficult to swipe an ATM card effectively, but you can fix the problem with one of several techniques. If the problem occurs frequently, it's a sign that the stripe is wearing down and becoming demagnetized. At this point, it's best to contact your financial institution to request a new card.

Step 1

Check your card for dust, dirt or lint. This is a possible problem if you store your card loosely in your purse, wallet or pocket. Any debris on the strip can interfere with the process of reading the delicate magnet bars. Wipe the back of the card clean on a piece of cloth or on your clothing before swiping it through the card reader.

Step 2

Cover the strip on the card to mask errors. Scratches, dirt and exposure to magnets, such as from the clasps on a purse, affect the arrangement of the magnetic bars on the strip. The scanner can overlook slight errors when it's covered. Slip the card into a plastic bag, hold the bag taut around the card so there are no wrinkles and slide it through the card reader. You could also cover the card with paper, like a receipt, or masking tape. Note that some machines, like ATMs that retain the card until the transaction is complete, might not have allowance for the plastic covering,

Step 3

Slide the card quickly through the card reader or ATM. The machines are programmed to scan the strip at a particular speed, which is why most of them advise the customer to insert and remove the card quickly. They are unable to read the information if you slide your card at a slower rate.