A method and a system for detecting and rewarding the returning of shopping carts to the supermarket collection points is provided. During shopping, a first signal A is generated. When a shopping cart is returned, a signal B is generated. These two signals A and B are correlated either in the supermarket or in an information device that the customer carries with him or her, in order to deliver a reward for returning the shopping cart. When the first signal A is generated, the customer or an information device carried with the customer is identified. Alternatively, the signal is provided to the customer at the supermarket checkout so that the customer himself/herself can take steps for the correlation of the signal A with the signal B that is still to be obtained.