This is what is mentionned on the ICAA website
[h=3]I cannot provide a reference from my employer as the business/company is no longer operating will you accept anything else[/h]If you are unable to provide a reference from an employer we may not be able to take that period of employment into consideration when assessing work experience.
Applicants applying for assessment within Australia are to provide the below information in a Statutory Declaration witnessed and signed by an authorised person. For a statutory declaration signatory list please check the Statutory Declaration Signatory List.
Applicants applying for assessment outside of Australia are to provide the below information in an affidavit witnessed and signed by a Public Notary within that country.
The reason/s why you cannot provide a reference and explain in detail the nature of your employment with the ceased business/company. Also include the dates of employment/length of business
Attach supporting third party documentation such as taxation certificates, employment contracts, payslips, and any other relevant information that verifies employment