Eligible businesses and individuals have until the 20th of September to lodge their priority applications.
Otherwise domains become available to the general public on the 3rd of October.
More than 200,000 registrations have been received to date for new domain names for what she says is a very trusted domain for potential customers.
Small Business Ombudsman Bruce Billson says not many realise this change is even taking place.
"Our field evidence is no-one had the foggiest idea this was going on. So we've engaged with the non-government regulator and said look, I know you've been busy talking with digital service providers and platforms. That's great, but it's not them that has to take the action to register the name. It's actually the small and family business."
Ross Widdows is a cyber expert.
He says the domain name change can work to the advantage of businesses.
"Organisations and people love to buy local, and it makes it easy for the first time to have a really short, sharp dot au website domain address in a really crowded internet marketplace."
