Abstract: A credit transaction system for adjusting the amount of money that can be used for credit according to the payment capability of the member, even when the credit limit for purchasing a product or receiving provided services with a credit card is set. In this system, in response to an application for a credit transaction, a computer calculates an adjusted unused balance based on an a preset adjustment rate for the credit limit of the member applying for the transaction, and based on a result of comparing the calculated adjusted unused balance with the transaction amount, the computer sets whether or not to allow the transaction.