What is CSC number? 09 March 2021 10:53 CSC number is your credit card security code which is a 3 or 4 digit number usually printing on the back of your credit number. CSC number is required to protect you and help prevent fraud. Related articles If I do not want to give out my credit card details, is there an alternative to make the payment? Are your prices in Australian Dollars? Is Lay-by available? Do you sell gift cards?