Child Support in Australia: Assessment, Disputes & When You Need a Lawyer
Updated 22 September 2026 · General information, not legal advice
Child support in Australia is assessed by Services Australia under the Child Support (Assessment) Act 1989 (Cth), using a formula based on both parents' incomes and each parent's percentage of care. A lawyer is usually involved only when a parent makes a binding child support agreement, applies to depart from the formula, challenges a decision beyond an objection, or goes to court.
If you disagree with an assessment, the first step is an objection to the Child Support Registrar within 28 days of the decision notice. If the formula does not suit your family's circumstances, the step is a change of assessment (departure) application. Parents who want certainty often use a binding child support agreement, which requires each party to get independent legal advice, and our ranked list of family lawyers in Australia compares firms that do this work.
When do you need a child support lawyer?
You need a child support lawyer when the law requires legal advice or when the dispute turns on legal argument rather than data entry. The common situations are:
- Binding child support agreement. Each party must receive independent legal advice and a signed lawyer's certificate before signing, under section 80C.
- Terminating a binding agreement. A termination agreement has the same legal advice requirement, under section 80D.
- Departure application with complex income. Business income, trusts, company structures and earning capacity arguments under section 117(2)(c) often need legal and accounting evidence.
- Setting aside a child support agreement. Only a court can set an accepted agreement aside, under section 136.
- Court departure orders. A court can depart from an assessment under section 116, usually when family law proceedings are already on foot.
- Review at the Administrative Review Tribunal (ART), or an appeal. An appeal from the ART on a question of law goes to the Federal Circuit and Family Court of Australia (Division 2).
- Support for a child aged 18 or over. Child maintenance for an adult child who is completing education or has a disability is a court order under section 66L of the Family Law Act 1975 (Cth), not a Services Australia assessment.
Both sides use lawyers in these matters: the parent paying child support (the liable parent) and the parent or carer receiving it (the carer entitled to child support).
How is child support assessed?
Child support is assessed by the Child Support Registrar (Services Australia) after a parent or eligible carer applies. A parent can apply under section 25 if they are not living with the other parent as a couple. A non-parent carer, such as a grandparent, can apply under section 25A.
The basic formula in section 35 works through eight steps:
- Work out each parent's child support income (broadly, adjusted taxable income less a self-support amount).
- Add the two incomes to get the combined child support income.
- Work out each parent's share of that combined income (income percentage).
- Work out each parent's percentage of care.
- Convert each percentage of care to a cost percentage.
- Subtract the cost percentage from the income percentage to get each parent's child support percentage.
- Work out the costs of the child from the combined income.
- A parent with a positive child support percentage pays that percentage of the costs of the child.
Services Australia applies the dollar figures and thresholds, which change each year. Different formulas apply where there are children from more than one relationship, a non-parent carer, or a parent who is overseas or deceased.
Child support stops when the child turns 18, among other terminating events in section 12. Under section 151B, a carer can apply for it to continue until the end of the school year if the child turns 18 while in full-time secondary education.
What is a change of assessment (departure)?
A change of assessment, called a departure in the Act, is a decision to move away from the formula because of special circumstances. The liable parent or the carer can apply to the Registrar in writing under section 98B while an assessment is in force.
The Registrar must be satisfied that at least one ground in section 117(2) exists, and that the change is just and equitable for the child and both parties and otherwise proper. The grounds fall into three groups.
| Ground group (section 117(2)) | Examples |
|---|---|
| (a) A parent's capacity to pay is significantly reduced | Duty to support another child or person, special needs of another child, necessary commitments, high costs of spending time with another child |
| (b) The costs of the child are significantly affected | High costs of spending time with the child, special needs of the child, high child care costs for a child under 12, costs of care or education the parents expected |
| (c) The assessment is unjust and inequitable | The child's own income or property; a parent's income, property, financial resources or earning capacity; payments or property transfers already made for the child's benefit |
A departure can generally reach back no more than 18 months before the application, unless a court gives leave. Section 117 also sets thresholds. For example, costs of spending time with a child, or child care costs, count as "high" only if they exceed 5% of the parent's adjusted taxable income for the period.
Under section 98B(2), the liable parent and the carer are both parties, so the other side can respond with their own evidence.
What are child support agreements?
Child support agreements let parents, and non-parent carers, set child support by agreement instead of relying only on the formula. There are two types.
| Feature | Binding child support agreement | Limited child support agreement |
|---|---|---|
| Section | 80C | 80E |
| Legal advice required | Yes, independent advice for each party with a signed certificate | No |
| Assessment must already exist | No | Yes |
| Minimum amount | None; can be more or less than the formula | At least the formula amount |
| Can it be varied? | No (section 80CA); it must be replaced or ended | No (section 80F); it must be replaced or ended |
| How it ends | New binding agreement, termination agreement with legal advice, or court order (section 80D) | New agreement, written termination agreement, court order, or notice by one party after 3 years or if the formula amount changes by more than 15% in circumstances the agreement did not contemplate (section 80G) |
| Grounds for a court to set it aside (section 136) | Fraud or non-disclosure; undue influence, duress or unconscionable conduct; exceptional circumstances since signing causing hardship | Fraud or non-disclosure; undue influence, duress or unconscionable conduct; significant change in circumstances; the rate is not proper or adequate |
A binding agreement gives certainty to both sides, and that certainty cuts both ways. A payer who later loses income, or a payee whose costs rise, is held to the agreement unless a court sets it aside for exceptional circumstances. That is why the law requires independent advice before signing.
Agreements can also include lump sums and non-periodic payments, such as school fees, which reduce or are credited against the child support payable.
How do you dispute a child support decision?
You dispute a child support decision in three stages under the Child Support (Registration and Collection) Act 1988 (Cth):
- Objection. Lodge an objection with the Registrar within 28 days after the decision notice is served, or within 90 days if you live in a reciprocating overseas jurisdiction (section 81). You can ask for an extension of time if you are late (section 82).
- ART review. If the objection decision is unfavourable, apply to the Administrative Review Tribunal for review (section 89). The other parent can also apply for review of an objection decision.
- Appeal on a question of law. A party to an ART review can appeal to the Federal Circuit and Family Court of Australia (Division 2) on a question of law only.
Most people handle the objection themselves. Legal help is more common at the ART stage and essential for an appeal.
When does a court decide child support?
A court decides child support only in limited cases. The main ones are:
- Departure orders under section 116, where family law proceedings are already pending and the court agrees to consider child support in them, or where the assessment is at the minimum annual rate.
- Setting aside a child support agreement under section 136, with consequential orders under section 137.
- Adult child maintenance under section 66L of the Family Law Act, for a child aged 18 or over completing education or with a disability.
Child support cannot be included in consent orders. It sits outside the property and parenting system, which is covered in our guides to parenting orders in Australia and property settlement after separation.
How much does a child support lawyer cost?
A child support lawyer's fees vary by firm, city and complexity, and are indicative only as at September 2026. Advice and a signed certificate for a binding child support agreement is often offered as a fixed fee, commonly in the range of about $1,500 to $4,000 per party. Departure applications and ART reviews are usually billed hourly, with total costs from a few thousand dollars to over $10,000 where business or trust income needs expert evidence. Court proceedings cost more.
Free help is available for some people. Legal aid commissions and community legal centres offer free and low-cost family law advice, and our guide to legal aid in Australia explains who is eligible.
Editor's picks
Chosen by our editors from verified facts and always labelled. Shown separately from the data-ranked list. How we rank law firms
Family Lawyer Associates
Dedicated family law practice covering separation, property, parenting and international matters nationally.
Melbourne VIC
View firm profile
Pearce Webster Dugdales
Established Melbourne firm with Law Institute of Victoria accredited specialists across family, property and commercial law.
Southbank VICGeelong VIC
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Doyle's Family Law & Mediation
Family law firm offering both mediation and litigation for property, parenting and divorce matters.
Hawthorn VICLorne VIC (by appointment)
View firm profile
AM Legal
Long-established South Australian practice combining family, estate and commercial law with notary services.
Aldinga SA
View firm profileFinding a family lawyer for a child support dispute
Look for a lawyer who regularly prepares child support agreements and departure applications, and who can work with an accountant on business or trust income. Compare fixed-fee options for agreement advice and check for an accredited family law specialist. Start with the ranked list of family lawyers in Australia, or compare family lawyers in Sydney, family lawyers in Melbourne, family lawyers in Brisbane and family lawyers in Perth.
Frequently asked questions
Do you need a lawyer for child support?
Not for a standard Services Australia assessment. A lawyer is required for a binding child support agreement, because each party must receive independent legal advice under section 80C of the Child Support (Assessment) Act 1989 (Cth), and is commonly used for departure applications and court proceedings.
How long do you have to object to a child support decision?
An objection must generally be lodged within 28 days after notice of the decision is served, or within 90 days for a person living in a reciprocating overseas jurisdiction, under section 81 of the Child Support (Registration and Collection) Act 1988 (Cth).
When does child support stop?
Child support stops when the child turns 18, among other terminating events in section 12 of the Child Support (Assessment) Act 1989 (Cth). If the child is in full-time secondary school, the carer can apply for it to continue to the end of that school year.
Can consent orders include child support?
No. The Federal Circuit and Family Court of Australia does not make child support orders on an Application for Consent Orders. Child support is dealt with by Services Australia or by a child support agreement.
Can a binding child support agreement be changed?
No. A binding child support agreement cannot be varied. It can only be ended by a new binding agreement, a termination agreement made with legal advice for each party, or a court order setting it aside.