The circumstances governing whether a "de facto” relationship will be imposed by Australian law for the purposes of making an application to the Family Court for a financial property settlement generally can only arise when one of the following legally prescribed circumstances is present :
1️⃣ Two adult persons who are not married or related by family live together as a couple in a "genuine and permanent domestic relationship” for at least two years (this can include more than one period providing it totals at least 2 years);
2️⃣ There is a child of the relationship;
3️⃣ There have been significant contributions made and a serious injustice would result if the court did not make an order or declaration; or
4️⃣ The de facto relationship has been registered in a State or Territory under laws for the registration of relationships.
In the recent case of Radecki & Fairbairn  FamCAFC 307 the Full Court of the Family Court of Australia at Sydney in their judgment dated 11 December 2020, confirmed the relevant law to determine the existence of a de facto relationship from para. 26 as follows:
A de facto relationship exists where a Court finds that the parties were “a couple living together on a genuine domestic basis” (s 4AA(1)(c) of the Act), which is to be decided by reference to the matters set out in s 4AA(2) of the Act, which are as follows:
(a) the duration of the relationship;
(b) the nature and extent of their common residence;
(c) whether a sexual relationship exists;
(d) the degree of financial dependence or interdependence, and any arrangements for financial support, between them;
(e) the ownership, use and acquisition of their property;
(f) the degree of mutual commitment to a shared life;
(g) whether the relationship is or was registered under a prescribed law of a State or Territory as a prescribed kind of relationship;
(h) the care and support of children;
(i) the reputation and public aspects of the relationship.
In addition, the Court “is entitled to have regard to such matters… as may seem appropriate to the court in the circumstances of case” (s 4AA(4) of the Act).
In a passage which has been frequently quoted and applied when determining the existence of a de facto relationship (see, for example, Sinclair & Whittaker (2013) FLC 93-551 (“Sinclair & Whittaker”) at  and Cadman & Hallett (2014) FLC 93-603 (“Cadman”) at ), albeit in a different legislative context, Fitzgerald J said in Lynam v Director-General of Social Security(1984) FLC 91‑577 at 79,663:
Financial arrangements cannot be taken in isolation and considered of particular importance in determining the nature of relationship.
Their materiality, like each of the other elements of the relationship, stems from the impact which they have as part of an overall situation.
Each element of a relationship draws its colour and its significance from the other elements, some of which may point in one direction and some in the other.
What must be looked at is the composite picture.
Any attempt to isolate individual factors and to attribute to them relative degrees of materiality or importance involves a denial of common experience and will almost inevitably be productive of error.
The endless scope for differences in human attitudes and activities means that there will be an almost infinite variety of combinations of circumstances which may fall for consideration.
In any particular case, it will be a question of fact and degree, a jury question, whether a relationship between two unrelated persons of the opposite sex meets the statutory test.
Although not expressly mentioned in s 4AA(2) of the Act, an intention to enter into a de facto relationship or to end one is powerful evidence to be taken into account under s 4AA(4) of Act, in determining whether such a relationship exists or has ended.
Whilst evidence of such intention is not required and, in many cases, is not present, where such an intention can be identified, it can be telling.
 s. 90SB of the Family Law Act 1975 (Cth.).
 Joint judgment of May, Strickland & Ainslie-Wallace JJ reported at 86,682.
 Paragraph 94 of the joint judgment of Bryant CJ, Thackray & Aldridge JJ reported at 87,398.
This FAQ was written by James D. Ford GAICD | Principal Solicitor, Blue Ocean Law Group℠.
This FAQ is intended for general interest + information only.
It is not legal advice, nor should it be relied upon or used as such.
We recommend you always consult a lawyer for legal advice specifically tailored to your needs & circumstances.