Understanding Paternity Law

hand holding baby hand
Paternity Law is complex, and can be hard to understand. There are many legal presumptions, financial issues, and dispute possibilities to be aware of.

In most circumstances when a child is born, family law presumes who the child’s parents are, ie. what the paternity or parentage of the child is. This presumption remains, until more persuasive evidence to the contrary is brought to light. 

Legal presumptions around paternity law

Although there may be countless variables and circumstances in which a child is born, some of the more common circumstances, to which this presumption applies, are as follows:

  1. if a child is born to a married woman, the husband is presumed to be the father;
  2. if a child is born to a married woman within 44 weeks of her separation from her husband, the husband is presumed to be the father;
  3. if a child is born to a woman within 44 weeks of her marriage being annulled or the husband dying, the husband is presumed to be the father;
  4. if a child is born to a woman who was living with a man from 44 weeks prior to 20 weeks prior to the birth of the child, this cohabitant man is presumed to be the father. It should be said, although the legislation is ambiguous, that the parties need to be a couple/in a relationship of some description for the presumption to apply. Obviously, where the father is unknown, the guy living on the bottom floor of the share house is not determined by the State to be the child’s father – but the legislation does merely say “cohabited”;
  5. a person entered as parent of the child on the birth register; and
  6. presumptions about paternity can also be made through court findings or signed acknowledgements;

Again, this is largely a practical starting point. The presumption merely operates in the absence of evidence to the contrary.

It also appoints an evidentiary burden of proof on the appropriate party should someone seek to challenge the paternity, meaning they are obligated to provide evidence. Once the presumption is challenged, the child’s paternity will then be determined on the basis of all the evidence.1

Financial issues related to paternity

For obvious reasons, verifying who a child’s parents are is of indispensable importance. The parents, the child and society have a vested interest in the correct outcome.2 In the usual course of things, where uncertainty arises, it is usually attached to the father.

From here, self-evident parenting issues can arise such as: who cares for the child and when; who is responsible for the child; who makes decisions for the child and how much of this is shared, and so on.

However, we’re often asked to also advise parties about the financial implications involved in disputed paternity matters. 

The most common financial implication stemming from paternity is that fathers are often liable to pay the mother child support. However, determining the paternity of a child has other consequences on financial family law matters.

Hypothetical circumstance

A couple date for six months and then move in together and live happily as a couple for 12-months. They maintain separate bank accounts but each pay for things for the other and so it goes. During the relationship, the woman falls pregnant and gives birth to a child, presumably, the man’s. After living together for the 12-month period, the parties who don’t own any joint assets decide to amicably separate. Upon separation, the financial implications for the parties, aside from child support, can vary as follows:

  1. if the man is not the biological father of the child, it is unlikely the relationship would be categorised as a de facto relationship. Therefore, the parties go their separate ways, keep their own assets and liabilities and neither can make a claim against the other’s assets; however
  2. if the man is the biological father of the child, it is likely the relationship would be categorised as a de facto relationship. Therefore, both parties can ask the court to make an order adjusting the property of the relationship in their favour. Further, the child’s primary carer (usually the mother) will, quite rightly, receive more than otherwise as she has the care and expense of the child, coupled with a reduced earning capacity.   

How paternity law disputes are resolved

Nowadays, paternity can be conclusively proven through DNA testing. However, a court will not order a party to undertake such tests without good cause.  

Before a paternity test will be ordered, the applicant must put forward evidence of an honest, bona fide and reasonable belief for their doubts surrounding the paternity of a child.3 At first instance, evidence will be given, which isn’t particularly pleasant but ultimately inescapable, about the date of conception, relevant sexual history and contraceptives. 

If the court is satisfied, they will then order the relevant party(ies) to undertake paternity testing. The types of paternity testing that can be taken are as follows:

    1. red cell antigen blood grouping;
    2. red cell enzyme blood grouping;
    3. HLA tissue typing;
    4. testing for serum markers; and
    5. DNA typing.4

Paternity tests have for a long time now, been viewed by courts as largely irrefutable. The Family Court of Australia accepts that paternity is now more a medical issue than a legal one. Paternity tests are likely to conclusively determine one way or another who the parents are without relying on challenged evidence about past events, credibility and presumptions.


The take home point for paternity law is that knowing who a child’s parents are, is a very important factor. In the usual course of things, there is a starting point presumption about who the parents are. To rebut this, you need to bring honest and reasonable evidence before the court. If you do so, a paternity test will be ordered and that will settle the matter.   

The above is general in nature and is not intended as legal advice. You should obtain legal advice in relation to your own specific circumstances.

 1. Moszko v Warshall (unreported, VSC, Smith J, 8572 of 1992, 20 February 1995), Smith J at 14.
2. G v H
(1993) 113 FLR 440, 441.
3. Duroux v Martin (1993) 116 FLR 141, 147.
4. Family Law Regulations 1984 (Cth), reg 21C.



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