The Constitution Alteration (Simultaneous Elections) Bill 1974, was an unsuccessful proposal to alter the Australian Constitution to require simultaneous elections for the House of Representatives and the Senate. It was put to voters for approval in a referendum held on 18 May 1974. Previous elections to the House of Representatives and the Senate had usually held simultaneously although this was a matter of convention rather than constitutional law. Election terms had lost synchronisation in the 1960s with separate half Senate elections in 1964, 1967 and 1970.