It is a serious offence to misrepresent yourself, or one of your family members when making an application for an Australian visa. This includes making false or misleading statements, or submitting false information or false documents with your application.
Even if someone else completes your application for you, you are responsible for it.
On 2 April 2011, the department introduced a Public Interest Criterion (PIC) which allows certain visa applications to be refused where false or misleading information is provided to the department.
It is better to explain why you do not have a document than to submit a false document with an application.
See: Introduction of Fraud Public Interest Criterion ( 87KB PDF file)