Abstract: The invention pertains to a stacking device for flat, upright mail pieces of different sizes, with a support (5) for holding the stack which can be displaced in the stacking direction in accordance with the thickness of the stack, and with a stacking point, to which the mail pieces (1) are transported in order to form the stack. The invention is characterized by the fact that the support (5) is arranged such that it can, during the course of its movement in the stacking direction, be displaced from a lower position, in which it reliably holds the largest portion of the front side or the rear side of the smallest mail pieces (1), into an upper position, in which the lower portion of the support (5) is situated underneath the upper edge of the smallest mail pieces (1) and the upper portion of the support (5) is situated above the center of gravity of the largest mail pieces (1).