Cardholders of a Citi Prepaid Card can check their balances online on the Citibank website at Na.CitiPrepaid.com. Several options are available, including registering one's card to an account, which allows direct future access without needing to enter the card details each time.
Registering one's card requires the ZIP code to which the card was mailed, the 16-digit card number, and the security code found on the back of the card, according to Citibank. Once registered, cardholders can log in to view their balances with a user name and password. Alternatively, it is possible to use the card number and security code to view the current card balance without registering it, and to view the full transaction history of the card by also providing the ZIP code.