Parliament is about to sit for the last time before the election.
Thursday is its final sitting day and it will be dissolved on Tuesday, which has to happen before an election can be held.
The Governor-General, acting on the advice of the Prime Minister, issues the proclamation.
It will be read on the steps of parliament, with the public invited to watch, by the Herald of Arms Extraordinary to The Queen, Phillip O'Shea.
All business before the House will be suspended, to be reinstated by the next Parliament.
The next step is Writ Day, on Wednesday, when the Governor-General instructs the Electoral Commission to hold the election.
Advance voting starts on September 11 and the election is on September 23.