An example cart inventory system and associated methods are described. The example cart inventory system includes a cart and a detection system. The cart includes a frame, and a shelf movably mounted to the frame and configured to be positioned between an extended position and a folded position. A top surface and a rear surface of the shelf include first and second identifiers, respectively. The detection system is configured to detect the first identifier when the shelf is in the extended position and detect the second identifier when the shelf is positioned in the folded position. In the extended position, the top surface is oriented upwards relative to horizontal and the rear surface is disposed against the frame. In the folded position, the rear surface is oriented upwards relative to horizontal.