It would be difficult to not be classed as defacto if you are living together.
In NSW see http://www.austlii.edu.au/au/legis/nsw/consol_act/pa1984298/s4.html
PROPERTY (RELATIONSHIPS) ACT 1984 - SECT 4
De facto relationships
4 De facto relationships
(1) For the purposes of this Act, a de...