Hi David, thanks for your question. In Australia, the timetable for federal elections is determined by the Australian Constitution and the Commonwealth Electoral Act 1918. A federal election must be held at least once every three years, and the Prime Minister chooses the election date within that 3-year term. The House of Representatives is then dissolved – brought to an end and the government becomes a caretaker government. Traditionally caretaker governments do not make major decisions, except in consultation with the opposition. The sittings of the Senate cease, but Senate committees may still meet.
The constitution does not make provisions for an election not being held. The Australian Electoral Commission (AEC) is the independent body responsible for running elections and may decide to run the election slightly differently to past elections. For example postal voting could be used more widely if the risk of voting in person is too high. For more information on elections look at the Australian Constitution online or the AEC.