A cart (2) for assisting in transferring mailpieces (100) for a sorting machine (1) having a row of sorting outlets (10) for the mailpieces (100) stacked on a work surface (11), said cart (2) for assisting in transferring mailpieces including a support (23) supporting a tray (101) to be filled, a back plate (20) carrying guide means (24) co-operating with a longitudinal runner (14) on said sorting machine (1), said back plate (20) being extended by a transfer ramp (26) inclined relative to said back plate (20) with which it forms an acute angle and designed to bridge over the edge of the work surface (11) to come flush with said work surface (11) from above. A postal sorting installation including a sorting machine (1) and a cart (2) as described for assisting in transferring mailpieces.