Money for the children is where some of the rawest feelings in a separation tend to surface — partly because it never really feels like it is only about money. Most child support in Australia is worked out by a government formula rather than a court, which surprises people. Where I help is the parts the formula does not handle well: agreements that give certainty, reviews when the assessment does not match your real circumstances, and the situations the standard calculation was never designed for.
How child support is actually calculated
Most child support in Australia is an administrative assessment by Services Australia (Child Support) under the Child Support (Assessment) Act 1989 (Cth) — not a court order. The formula combines both parents' incomes, the percentage of care each provides (broadly measured in nights per year), and the published costs of children for each age group. Because it is a formula, the result can feel impersonal and occasionally unfair, even when it is correctly applied.
Understanding the formula is the first step, because it shows where there is genuine room to move and where there is not. Many disputes are really disputes about the inputs — income and care percentages — rather than the formula itself.
Child support agreements — binding vs limited
Parents can step outside the formula by agreement. A binding child support agreement requires each parent to have independent legal advice and can set child support at any agreed amount — above or below the formula — with strong stability, which suits parents who want certainty. A limited child support agreement does not need legal advice but must be at least the formula amount and can be ended after three years or on a significant change of circumstances.
I help parents decide which type fits, draft the agreement, and make sure it is registered correctly so it is enforceable rather than just a handshake.
When the formula doesn't fit: change of assessment and adult children
Where the formula produces an unfair result, a parent can apply for a change of assessment in special circumstances — for example high costs of spending time with a child, the special needs of a child, or where a paying parent's true earning capacity is not reflected in their taxable income. These applications turn on evidence, and they are where legal help earns its keep.
Child support normally ends when a child turns 18 or finishes secondary school, but in defined cases the Court can order adult child maintenance — typically where a child over 18 is completing tertiary study or has a disability. I advise on whether that applies in your situation.
How I handle a child support matter
- 1Free initial conversation about your circumstances and the current assessment
- 2Plain-English explanation of how the formula applies to you
- 3Advice on whether an agreement or a change of assessment is the better path
- 4Drafting and registration of a binding or limited child support agreement
- 5Help preparing a change-of-assessment or adult child maintenance application
Frequently asked questions
How is child support calculated in Australia?
Child support in Australia is usually calculated by Services Australia under the Child Support (Assessment) Act 1989 (Cth), using a formula that combines both parents' incomes, the percentage of care each provides, and the published costs of raising children by age. It is an administrative assessment rather than a court order, though parents can agree on a different amount.
Can we agree on our own child support amount?
Yes. Parents in Australia can make a binding child support agreement, which requires each parent to obtain independent legal advice and can set any agreed amount, or a limited child support agreement, which needs no legal advice but must be at least the formula amount. I help parents choose the right type and draft it so it is enforceable.
Can I challenge a child support assessment?
Yes — if the formula assessment produces an unfair result, you can apply to Services Australia for a change of assessment in special circumstances, such as high costs of care, a child's special needs, or a paying parent's real earning capacity. These applications turn on evidence, so legal help in preparing them often makes a real difference.
Does child support stop at 18?
Child support in Australia generally ends when a child turns 18 or finishes secondary school. In defined cases a court can order adult child maintenance beyond that — usually where the child is completing tertiary study or has a disability. Whether it applies depends on the specific circumstances, which I can assess with you.
Reviewed by Elisa Rothschild BA/LLB — Principal Lawyer, Fogarty Oliver Rothschild. Admitted to legal practice in Victoria. Last reviewed 2026-06-21.
This page is general legal information about child support in Victoria, Australia. It is not legal advice for your specific situation. For advice on your matter, book a free initial consultation.