Statements made by a party to third parties or government organisations (most commonly Centrelink, the Australian Taxation Office and the Department of Immigration) which contradict their evidence to the Family Court may not be fatal to their application for a finding of de facto relationship status.
Put simply, telling someone you’re in a de facto relationship doesn’t mean you are (and vice versa).
This situation arose in Benedict v Peake  FCCA 332 when a de facto wife who had previously asserted to Centrelink and the Australian Taxation Office she was not in a de facto relationship now sought to lead evidence before the Court that a de facto relationship had in fact existed for 17 years.
This is the ‘Elias principle’, a notion that “… when a party has made representations of fact to third parties and has gained advantage from so doing, it is open for the court in subsequent proceedings under section 79 of the Family Law Act to decline to accept from that party evidence which contradicts those representations.”
The Court has discretion whether to apply this principle, and this depends on all of the circumstances of each case.
Justice Chisholm In the Marriage of Jordan (1997) said:
“… When a party has made representations of fact to third parties and has gained advantage from so doing, it is open to the court in subsequent proceedings… to decline to accept from that party evidence which contradicts those representations.”
If such representations need to be made, they may carry criminal or other penalties. The person providing such evidence should consider obtaining certificate against incrimination under the Evidence Act.