A system and a method for detecting and rewarding the return of supermarket carts or luggage carts taken from a cart stand. Each cart is provided with a contactless, preferably optically identifiable, individual mark, by which the cart is identified when it is returned to a cart stand. In addition, the identifying mark on the cart changes when the cart is brought back to the cart stand, from an active state, in which the mark can be identified, to a passive state, in which the mark cannot be identified, or vice-versa. In addition to the presence of a returned cart, the invention enables the correct positioning of a cart in a row of nested carts to be identified in a contactless and automatic manner.