Paying with a Credit Card Credit cards can be used to register on-line for the conference (MasterCard and Visa only). On the last page of this registration process, you will be asked to provide the billing information of your credit card including the credit card number, 3-digit security number (located on the back of the card) as well as the billing address.   If you have difficulties using your credit card on-line or receive an error message, please contact us. We can process a credit card payment offline if necessary.