A sealing member for sealing a toner discharge opening of a toner accommodating container detachably mountable to an image forming apparatus, the sealing member includes a locking portion for being locked with a portion to be locked provided in the image forming apparatus, the locking portion being adapted to displace with a relative closing movement relative to the portion to be locked, wherein the toner discharging opening is brought into an open state from a closed state by relative to movement of the sealing member relative to the toner accommodating container with the locking portion being in engagement with the portion to be locked; and a releasing force receiving portion for receiving from the image forming apparatus a releasing force for releasing engagement between the locking portion and the portion to be locked by displacing the locking portion.