From CASA’s aircraft register FAQs:
An entry in the Australian Civil Aircraft Register or a certificate of registration for an aircraft must not be viewed as conclusive evidence of the existence of a legal or beneficial property interest in the aircraft. This is clearly stated on the certificate of registration and in CASR 47.055. Financial interests in an aircraft can only be confirmed through whatever legal and commercial mechanisms are available outside of CASA. CASA does not require any proof of ownership with an application to become a registration holder. However, the applicant legally declares that they are the owner of the aircraft.
Parties with a financial interest in an Australian aircraft should ensure that they hold legally accepted documents to prove their entitlement to the aircraft (such as bills of sale, financial contracts, etc).