How child support is calculated in Australia
Child support is one of the biggest financial questions after separation. Services Australia usually calculates the amount using a set formula.
The formula is designed to share the cost of raising children between parents according to their financial capacity and the care they provide.
1. The formula is more than just income
The current system uses an 8-step formula. In simple terms, Services Australia works through:
- each parent’s child support income;
- the parents’ combined child support income;
- each parent’s income percentage;
- each parent’s percentage of care;
- each parent’s cost percentage;
- each parent’s child support percentage;
- the estimated costs of the children; and
- the final child support amount.
2. Step one starts with income
Services Australia generally starts with each parent’s adjusted taxable income.
It then deducts a self-support amount so that each parent is allowed an amount for their own living costs before child support is calculated.
3. Care percentage matters
Services Australia usually works out care as a percentage based on the amount of time each parent cares for the child.
| Care level | Care percentage | Approx. nights per year |
|---|---|---|
| Below regular care | 0–13% | 0–51 |
| Regular care | 14–34% | 52–127 |
| Shared care | 35–65% | 128–237 |
| Primary care | 66–86% | 238–313 |
| More than primary care | 87–100% | 314–365 |
Care percentage is then converted into a cost percentage. This represents the share of the child’s costs that Services Australia treats you as meeting directly while the child is in your care.
5. How are the costs of children worked out?
Services Australia uses annual Costs of Children tables. The amount depends on:
- the parents’ combined child support income;
- the number of children; and
- the ages of the children.
Children aged 13 and over are generally assigned higher costs than younger children.
For 2026, the formula caps the combined child support income used for the Costs of Children table at $232,843. Costs do not continue rising under the formula once combined child support income exceeds that cap.
6. A simple example
The actual amount requires the full formula, so an online child support estimator is more reliable than trying to apply a simple percentage to income.
7. What happens when care changes?
If the amount of care changes, the child support assessment may also change.
Services Australia says parents should report changes as soon as possible. If you tell them within 28 days, they can generally adjust the assessment from the date the care arrangement changed.
Reporting later can affect the date the new care level takes effect and may create an overpayment or debt.
8. What about school fees, medical costs and other expenses?
The basic formula does not simply add every family expense dollar-for-dollar.
In some families, parents separately agree about costs such as:
- private school fees;
- medical, dental or therapy costs;
- sport and extracurricular activities;
- uniforms and technology; or
- other substantial expenses.
If special circumstances mean the standard assessment does not properly reflect the child’s needs or the parents’ circumstances, a parent may be able to apply for a change of assessment.
9. Can parents make their own child support agreement?
Yes. Parents may be able to use a child support agreement instead of relying only on the standard formula.
There are different types of agreements and different legal requirements. A binding child support agreement, for example, requires independent legal advice for both parties.
10. What if income changes?
A change in income can affect child support. Services Australia generally uses income information from the financial year that ended before the current child support period, but there are rules allowing income estimates in some circumstances.
Parents should tell Services Australia about relevant changes rather than assume the assessment will automatically update immediately.
11. What happens when a child turns 18?
Child support normally ends when a child turns 18, but there are exceptions.
If the child will still be in full-time secondary education when they turn 18, the receiving parent may be able to ask for the assessment to continue until the end of that school year. The application needs to be made before the child turns 18.
12. Child support and parenting arrangements are separate
Paying child support does not buy time with a child
Parenting arrangements are based on the child’s best interests. Child support is about financial support.
A dispute about payments should not be used to stop a child spending time with a parent, and a parenting disagreement does not automatically remove a child support obligation.
The simple way to think about child support
Services Australia compares each parent’s share of the family income with the share of the child’s costs they are already meeting through care.
If your income share is higher than your cost share, you will generally be the parent who pays. If your cost share through care is higher, you will generally be the parent who receives child support.