Check on the issuer's website
- 1Open the balance website printed on the back of the card — it differs by issuer, so use the one on your card rather than a search result.
- 2Enter the 16-digit card number, the expiration date and the 3-digit security code.
- 3The current balance and recent transactions appear. Most issuers also let you register a ZIP code here, which many online stores require at checkout.