A panel for use in a system for forming concrete slabs, the system utilizing at least one said panel and at least one shore post having a top plate, said panel comprising: a rectangular flat upper surface having a notch at each corner thereof to accommodate one of said shore posts; a plurality of end rails, each of said end rails being affixed below an end of said upper surface; a plurality of side rails, each of said side rails being affixed below each side of said upper surface; a plurality of corner members, each corner member having a first end and a second end opposite said first end, each corner member being affixed to a corner of said upper surface; the first end of each corner member being affixed to an end of one of said end rails; the second end of each corner member being affixed to an end of one of said side rails; each of said corner members being disposed in a gap between the end of one said end rails and the end of one said side rails, such that said corner member is shaped to conform with said notch so as to accommodate one of said shore posts; and characterised by a plurality of legs, each leg extending downwardly from one of said corner members, and each leg including a foot adapted to fit into a cup in said shore post, said foot comprising a flanged lower surface and a notch above said flanged lower surface, wherein said plurality of legs are adapted to support said panel; and wherein each of said corner members further comprises a shoulder, each shoulder protruding outwardly from said corner member and each of said shoulders being adapted to engage the top plate of said shore post such that said panel is prevented from moving upwardly when engaged with the top plate of said shore post, in use. a rectangular flat upper surface having a notch at each corner thereof to accommodate one of said shore posts; a plurality of end rails, each of said end rails being affixed below an end of said upper surface; a plurality of side rails, each of said side rails being affixed below each side of said upper surface; a plurality of corner members, each corner member having a first end and a second end opposite said first end, each corner member being affixed to a corner of said upper surface; the first end of each corner member being affixed to an end of one of said end rails; the second end of each corner member being affixed to an end of one of said side rails; each of said corner members being disposed in a gap between the end of one said end rails and the end of one said side rails, such that said corner member is shaped to conform with said notch so as to accommodate one of said shore posts; and characterised by a plurality of legs, each leg extending downwardly from one of said corner members, and each leg including a foot adapted to fit into a cup in said shore post, said foot comprising a flanged lower surface and a notch above said flanged lower surface, wherein said plurality of legs are adapted to support said panel; and wherein each of said corner members further comprises a shoulder, each shoulder protruding outwardly from said corner member and each of said shoulders being adapted to engage the top plate of said shore post such that said panel is prevented from moving upwardly when engaged with the top plate of said shore post, in use.