To provide a method for preventing sales from being reprocessed when issuing a coupon.

This benefit information change method makes a computer perform: a step for receiving information related to sales commodities and information related to a purchase customer; a first confirmation step for confirming whether or not the purchase customer is included in destination information to notify benefit information related to a first commodity about the first commodity among the sales commodities in reference to a storage part managing the commodity, the destination information to notify the benefit information related to the commodity, and an access status to the benefit information; a second confirmation step for further confirming whether or not the information related to the purchase customer is included in information related to the access status when the information related to the purchase customer is included; and an update step for changing the benefit information related to the first commodity destined for the purchase customer when the information related to the purchase customer is not included.

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