Thanks for your reply.
The visa waiver program with Australia allows citizens to come here for short visits, but it's technically at the discretion of the Entry Clearance Officers at the Airport because they have the discretion to refuse entry if they suspect a visitor shall overstay their visit and seek permanent stay (which is strictly prohibited).
Where visiting a partner the chances of an overstay are increased and the ECOs are more suspicious, hence your questioning.
You should certainly take evidence of your return ticket, money that you have available and also evidence of your accommodation, car and job in Australia to convince them that you have compelling ties back home which will mean you will return.
However, to be 100% certain of entry you would have to apply for a visitor's visa before you left. In these circumstances the chances of questioning are dramatically reduced because the ECO will be confident of the checks made by their officers on your visitor's visa applications. You may be pushed to get a visa by that time and if minded to do so would call the embassy to see if they do same day appointments.
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