If you've lost your credit or debit card, suspect it was stolen or think someone has lifted your number off the Internet, call your card issuer immediately. Credit cards offer the greatest protection against fraud. Most card issuers provide zero-liability fraud protection, and federal law says once you report the loss or theft, you have no further responsibility for unauthorized charges. Your maximum liability under federal law is $50 per card.
With debit cards, your responsibilities and rights change. While you may have zero-liability fraud protection on your debit card, it may not apply to PIN-based transactions or ATM withdrawals. Federal law also has some caveats when it comes to debit card fraud protection. If someone made fraudulent purchases with the debit card data and you don't report the theft immediately, your liability could skyrocket, especially if you wait longer than 60 days to report it. In addition, if a thief uses your debit card to drain your bank account, you'll be short on cash while your bank investigates.