There are several ways to tell on each check. Credit card checks usually have an expiration date on them, for example "Use before October 10, 2004". A somewhat more obscure way to see is if the check is from one of the major credit card banks such as BankOne, CapitalOne, etc. Since we only cash checks for customers, the likelihood that one of our customers would have a check from a large bank would be minute. This would cause us to take a closer look at the check and then you can usually see other differences. Also the name and address usually looked typed versus the printing from regular printing companies. Sometimes it will have the customer's account number on them but the MICR line looks different from regular printed checks. In addition, many of them are not the same size as your basic check. Just a few observations I have made, hope it helps.