A bank signature card is a form used by banks to authenticate its customers' signatures for certain transactions. A bank account cannot be opened legally without the completion of a bank signature card. This card is kept on file at the bank, and is the primary means of identifying the user of a particular account.
For example, in the case of a checking account, a signature card is available to authenticate the signature on a particular check. A signature card is also used when a customer wants to access his safe deposit box. If a customer does not sign a signature card when opening a bank account, he might have difficulty accessing his money on his next visit.