The referendum is used in Australia as part of the formal process of amending the Commonwealth Constitution. Section 128 of the Constitution requires that a proposal to amend the Constitution must first take the form of a Bill submitted to the Commonwealth Parliament. Between two and six months after it leaves the Parliament, the proposal 'shall be submitted' to the voters in the States and Territories in the form of a referendum.

The Constitution originally provided that Bills to alter the Constitution had to be approved by referendum in a majority of States and by a majority of all electors voting. Following an amendment in 1977, the Constitution now allows electors in the Territories, as well as electors in the States, to vote in constitutional referendums. Territory votes are included in the national total only. No proposed amendment diminishing the proportionate representation of any State in either House of the Parliament, or the minimum number of representatives of a State in the House of Representatives, or altering the boundaries of a State, may become law unless the majority of the electors voting in that State approve the proposed law.

The Referendum (Machinery Provisions) Act 1984 provides the machinery for conducting referendums. Constitutional referendums have been held on nineteen separate occasions, involving forty-four separate amendment attempts.

Only eight of the forty-four proposals have been carried by referendum:

• Senate Elections (12 December 1906) made minor alterations concerning Senate elections and terms
  
  of Senators
• State Debts (13 April 1910) allowed the Commonwealth takeover of State debts
• State Debts (17 November 1928) formalised the position of the Loan Council
• Social Services (28 September 1946) gave the Commonwealth power to provide certain social services
• Aboriginals (27 May 1967) gave the Commonwealth power to make laws for Aboriginal people resident in the States and to include all Aboriginal people in the national census
• Casual Vacancies (21 May 1977) aimed at ensuring that a replacement Senator should be from the same party as the departing Senator
• Territory Votes (21 May 1977) gave residents of the Australian Capital Territory and the Northern Territory the right to vote in constitutional referendums
• Retirement of Judges (21 May 1977) provided for a retirement age of seventy for all federal judges.

National plebiscites

In Australia referendums on questions that do not affect the Constitution are usually called plebiscites. They have no legal force. Three national plebiscites have been held: two on the conscription of troops during World War I and one on a national song in 1977.

The following pages show the voting figures at each constitutional referendum* and national plebiscite. In all cases the italicised words provide the question asked of voters on the referendum ballot paper.

The numbering of the referendums and plebiscites has been provided for the convenience of the reader. It is not an official numbering.