A sales transaction support system according to an embodiment includes a server that stores records including a member code and a corresponding notification destination, and reward data indicating a reward content and a reward condition. A register device generates transaction data, and receives an input of a user code via the input device. If the user code corresponds to one of the member codes, the member code is added to the transaction data. The server receives the transaction data including the member code from the register device, and determines whether the reward condition is satisfied based on the transaction data. If the reward condition is satisfied based on the transaction data, the server transmits a notification of the reward content to the notification destination corresponding to the member code included in the received transaction data.