Why a referendum is required
The Commonwealth Constitution contains a special process for formal constitutional alteration. Parliament cannot normally change the Constitution simply by passing an ordinary bill. A proposed alteration must be put to voters in a referendum under section 128 after passing through the parliamentary process required for referendum proposals.
A referendum therefore asks voters to approve or reject a specific constitutional change, not to choose a government.
The double majority
For most constitutional alterations to pass, the proposal must achieve a national majority of formal votes and a majority of voters in a majority of states. With six states, that ordinarily means winning nationally and in at least four states. Special rules can also apply where a proposal affects state representation or boundaries.
This double-majority requirement is deliberately harder to satisfy than an ordinary national popular vote. A proposal can win more votes nationally but still fail if it does not secure enough states.
Parliament comes first
A referendum proposal begins with legislation to alter the Constitution. Parliament considers the proposed wording before the question goes to voters. The referendum campaign then focuses on whether voters should approve that precise constitutional alteration.
Because constitutional text can have long-term legal effects, reading the actual proposal and official explanatory material is more useful than relying only on campaign slogans.
Referendums are not plebiscites
In Australian political discussion, referendum and plebiscite are sometimes confused. A constitutional referendum is the legally prescribed mechanism for changing the Constitution. A plebiscite is a vote used to seek public opinion and does not itself amend the Constitution.
The legal effect and voting rules therefore depend on the type of national vote being held.
Where to verify a referendum claim
Use the Australian Electoral Commission for current voting information and referendum administration. Use the Constitution, referendum legislation and official parliamentary material for the legal text and process. Court judgments may later matter when constitutional provisions are interpreted.
For historical claims, check the AEC's referendum results rather than assuming that a proposal's national vote share tells the whole story.
Primary sources and further reading
We use authoritative Australian institutions as the starting point for this explainer. Follow these links for the underlying rules, official guidance and current details.