A casting vote is held by the chair, president, or speaker of a representative body. The position of chair (or president or speaker) is generally held to be neutral. The holder of the office only casts their vote if the votes from the remainder of the representative body are tied. If the votes are tied and the holder of the office chooses not to cast their vote, then the motion is determined in the negative.
Reference: Section 40 of the Commonwealth Constitution: Questions arising in the House of Representatives shall be determined by a majority of votes other than that of the Speaker. The Speaker shall not vote unless the numbers are equal, and then he shall have a casting vote.