E-Commerce Configuration Guide : Site Configuration Settings : Checkout Settings : AllowStoredCards
 
AllowStoredCards
Key value:
0 or 1
Description:
Enables (1) or disables (0) the display of the two Credit Card check boxes on the Checkout.aspx page: one to charge the sale to the card in the purchaser’s guest record (if the card is valid) and one to save the card being used into the guest record.
Note: Credit card numbers are viewable only when the visitor/guest first enters the number. After that, only the last four digits are displayed, if the card is valid or an indication is given that the card is not valid or not present. The GuestEdit.aspx page allows a visitor/guest to update (including blanking out) a card on file.
See also:
CreditCardTypeText