Whenever a vacancy occurs in the House of Representatives because of the death, resignation, absence without leave, expulsion, disqualification or ineligibility of a member, a writ may be issued by the Speaker for the election of a new member. A writ may also be issued when the Court of Disputed Returns declares an election of a member of the House of Representatives to be void.

A by-election may be held on a date to be determined by the Speaker, or, in the Speaker's absence from Australia, by the Governor-General in Council. The polling must take place on a Saturday.

The Acting Speaker performing the duties of the Speaker during the Speaker's absence from the Commonwealth may also issue a by-election writ. The Chairman of Committees as Deputy Speaker has also issued a writ during the Speaker's absence from the Commonwealth, and the Chairman of Committees as Deputy Speaker has informed the House of the Speaker's intention to issue a writ.

There are no constitutional or statutory requirements that writs be issued for by-elections within any prescribed period.

The following cases have occurred:

• with a federal election pending, the Speaker has declined to issue a writ in order to avoid the need for two elections within a short period of time, and
• a writ has been issued and then withdrawn by the Speaker when a dissolution of the House of Representatives has intervened.

The guiding principle in fixing the date of a by-election has always been to hold the election as early as possible so that the electors are not left without representation any longer than is necessary.

Source: House of Representatives Practice 5th Edition, p90.

1. Tas. voted as one at the by-election of 1902
2. These by-elections were not contested
3. Spelt 'Ballaarat' in the writ as the division name was spelt this way until 1977

A supplementary election must be held if a candidate for a House of Representatives election dies in the period between the close of nominations and election day. A new writ is issued for another election in that division, but the election is held using the electoral roll prepared for the original election. This provision is found in section 181 of the Act.

This provision was introduced in its current form in 1928 following the automatic election of Nationalist Party candidate, Grosvenor Francis, in the division of Kennedy. Mr Francis was elected after the death of the Labor candidate, Charles McDonald, who died the day before election day in 1925. Mr McDonald had represented the division of Kennedy from 1901 to 1925. As only two candidates nominated for the seat, the Nationalist member was automatically elected under the law of the day.

The first supplementary election occurred in the division of Hume in 1972. It was held on the same day as the 1972 federal election so was not classified as a separate election. This can no longer occur because of the minimum 33 day timetable between the issue of the writ and election day.

If a candidate for a Senate election dies in the period between close of nominations and election day, and the number of remaining candidates is not greater than the number of candidates to be elected, those candidates are declared elected. However, if the remaining candidates are greater in number than the number of candidates to be elected, the election proceeds. A vote recorded on a Senate ballot paper for the deceased candidate is counted to the candidate who received the voter's next preference.