(Card Verification Number) is an anti-fraud security feature to help verify that you are in possession of your credit or debit card. CVN is also known as CVV (Card Verification Value). For Visa, MasterCard, and Discover cards, including debit cards with the Visa or MasterCard logo, the CVN is a three-digit number printed at the top of the signature panel on the back of the card, immediately after the account number. For American Express cards, the CVN has four-digits and is printed on the front of the card above the account number. For added security, Boost Mobile requires this number in order to complete all purchase orders.