The fillable closure with a triggering pushbutton comprises a filler neck (3) that is to be screwed onto or joined to a container neck (4) as well as a closure cap (1) which is associated to the filler neck (3) and can be joined, pivoted and snapped-on the filler neck (3) by means of a hinge connection. A separately fillable container (2) can be inserted into the filler neck (3), the container being closed at the bottom with a sealing foil (19) that can be pierced or cut open. The closure cap (1) comprises a cap cover as a pusher disc (7), which can be pressed downward in the axial direction while deforming. By pressing the cap cover downward on the container (2) inserted in the filler neck or on a rigid opening element accommodated therein, the opening element can be pressed downward so that the sealing foil (19) of the container (2) can be pierced and cut open.