How can the Australian Constitution be changed?

The Australian Constitution can be changed only by a referendum under section 128 of the Constitution. The referendum requires what is called the double majority: a national majority of voters across Australia, plus a majority of voters in at least four of the six states. Voters in the two mainland territories count toward the national total but not toward the state-by-state count.

The process for a referendum begins with Parliament. A constitutional alteration bill must be passed by an absolute majority of both Houses of the federal Parliament (or alternatively by one House twice with a deadlock-breaking mechanism). The bill is then presented to the Governor-General, who issues a writ for the referendum. The referendum must be held not less than two months and not more than six months after the bill has been passed by Parliament. The Australian Electoral Commission runs the referendum on the same compulsory-voting basis as ordinary federal elections.

Of the 45 referendum questions held since federation, only 8 have been carried. The successful amendments are the 1906 referendum on Senate elections, the 1910 referendum on state debts, the 1928 referendum on Commonwealth-state finance, the 1946 referendum on social services, the 1967 referendum recognising Aboriginal people in the Constitution (carried with 90.77 per cent Yes, the highest Yes vote in any Australian referendum), the 1977 referendum allowing simultaneous Senate elections, the 1977 referendum setting retirement at 70 for federal judges, and the 1977 referendum on filling Senate casual vacancies.

The 37 defeated referendums include many proposals to expand Commonwealth powers (1911, 1913, 1919, 1926, 1937, 1944, 1973, 1984), the 1944 fourteen-powers proposal, the 1948 rents and prices referendums, the 1951 communist ban, the 1973 prices and incomes proposals, the 1988 fair elections and other proposals, the 1999 republic and preamble referendums, and most recently the 14 October 2023 referendum proposing an Aboriginal and Torres Strait Islander Voice to Parliament (defeated nationally with 60.1 per cent No, carried in no state). Constitutional change in Australia is therefore difficult, with the double-majority requirement operating as a strong filter against proposals that lack broad national and state-by-state support.