It is critical that you report the loss or theft of your credit cards to the card issuers as quickly as possible. This is true for both your personal and business-purpose credit cards.
Many companies have toll-free numbers and 24-hour service to deal with such emergencies. Credit card issuers often place instructions for reporting lost or stolen cards on your monthly statement. Follow those instructions.
It's a good idea to follow up each phone call reporting a card lost or stolen with a letter. Include the following information and any other information directed by the card issuer:
The full name on the account and the address associated with the account
When you noticed your card was missing
The date you first reported the loss
Be sure to keep a copy of the letter and send it to the address the credit card issuer designates for reporting lost or stolen cards, which might not be the same as for billing errors. Do not send it with a payment—or to the address where you send your payments—unless directed to do so.
If you report the loss before your credit cards are used, the card issuer cannot hold you responsible for any unauthorized charges made by a third party. If there is unauthorized use of your cards by a third party before you report them missing, the most you will owe for unauthorized charges by a third party is $50 per card.
Also, if the loss involves your credit card number, but not the card itself, you have no liability for unauthorized use by a third party. However, you should notify the card issuer of the unauthorized use as quickly as possible.
After the loss, review your billing statements carefully. If they show any unauthorized charge(s), write a letter to the card issuer describing each unauthorized charge. Again, tell the card issuer the information noted in the bullets above. Be sure to send the letter to the address provided for billing errors.