Preferences rank choices rather than selecting only one
Australian federal elections use preferential voting. Voters number candidates or groups in an order of preference, subject to the formal voting rules for the relevant ballot paper. During the count, preferences can be transferred when required to determine the elected candidate or candidates.
The principle is that a ballot can continue to express a voter's choices after an earlier preference can no longer help elect that candidate. The House and Senate use different counting methods because one elects a single member per electorate while the other elects multiple senators.
House of Representatives
For the House, voters rank every candidate on the green ballot paper. If no candidate has an absolute majority of formal first-preference votes, the candidate with the fewest votes is excluded and those ballots are transferred according to the next available preference. The process continues until a candidate has more than 50 per cent of the formal vote remaining in the count.
This means first-preference percentages matter, but they are not always the final result. A candidate who starts second can win after preferences are distributed.
Senate
The Senate is a multi-member proportional contest. Candidates are elected by reaching a quota. Voters can vote above the line for parties or groups, or below the line for individual candidates, following the AEC's formal numbering instructions. Preferences determine where votes transfer when candidates have surpluses or are excluded.
Because multiple seats are filled, the Senate count is more complex than the House count. The important voter-level point is that preferences written on the ballot determine the direction of transfers; there are no party-controlled group voting tickets in federal Senate elections.
Preference recommendations are not automatic transfers
Political parties often distribute how-to-vote material suggesting an order of preferences. Those recommendations can influence voters, but the ballot is counted according to the numbers the voter actually writes. A party does not own or mechanically redirect a person's vote.
This is an important distinction in campaign reporting. A preference deal is normally an agreement about recommendations and campaigning, not a legal transfer of votes between parties.
Always check the AEC for voting instructions
Formal voting requirements are legal rules, so the Australian Electoral Commission is the correct source for current ballot instructions. Campaign leaflets, social media and commentary should not replace AEC guidance when you are deciding how to complete a ballot paper.
This explainer describes the system at a general level and is not a substitute for official election instructions for a specific election.
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.