A foldable container comprises a box including a floor and sidewalls attached to one another to present a chamber. The box further includes foldable panels that shift from a retracted position within the chamber to an upright extended position. The extended panels serve to expand the chamber for containing a liquid or solid bulk material. The extended panels are interconnected by joints that resist tampering and that are tamper-evident. The container further includes a retaining assembly for securely holding the material in the chamber and a lid for covering the chamber. The lid cooperates with the panels to resist tampering and to be tamper-evident. The container also includes stanchions for selectively stacking at least two containers when the containers are storing the bulk material.