Understanding Your Result
The estimate above is produced using the legislated Australian child support formula. The calculator applies the same calculation used by Services Australia, but presents the result instantly so you can test different incomes, care arrangements, and numbers of children.
This is the only non-government calculator found to reproduce identical results for standard cases.
See verification.
The instant calculation method allows you to change inputs and immediately see how the assessment responds, making it easier to understand how income and care affect child support.
How This Child Support Calculator Works
We apply the official 8-Step Child Support Formula used by the Australian Government. The formula balances financial capacity against the level of care each parent provides.
Phase 1: The Income Pool
1. Calculate Available Income
We subtract the Self-Support Amount ($31,046 for 2026) from each parent’s taxable income to determine how much income is available for child support.
2. Combine Parents’ Income
Both parents’ available incomes are added together to form the Combined Child Support Income.
3. Determine Your Share
We calculate the percentage of the combined income that comes from you.
Phase 2: The Care Credit
4. Determine Care Percentage
Your number of nights per fortnight is converted into an annual care percentage.
5. Calculate Cost Credit
We apply the legislated Cost Percentage Table, which assigns a cost credit to your care level (for example, 14% to 34% care corresponds to a 24% cost credit).
6. Balance Income and Care
Your cost credit is subtracted from your income share to determine your net child support position.
Phase 3: The Assessment
7. Costs of the Children
We calculate the total cost of raising the children using the government’s five-band cost table, which increases as combined income rises.
8. Final Annual Amount
The total cost is multiplied by your net position.
• If the result is positive, you pay child support.
• If negative, you receive child support.
Exceptions for Low-Income Earners
Fixed Rate ($1,825 per year, per child)
This is the normal lower bound of child support in low-income cases. It applies automatically under the formula where a paying parent has low taxable income and less than shared care of the child. The calculator applies this rate automatically whenever the legislated rules require it. For a practical explanation, see Real minimum child support payment in Australia.
Minimum Rate ($551 per year)
This rate does not apply automatically. It is only available where the payer has a very low taxable income, did not receive income support during the relevant period, and successfully applies for an exemption. Because most genuinely low-income parents either receive income support or have received it at some point during the year, this rate applies only in uncommon cases.
Child support may also fall below the fixed rate, including to $0, where shared care applies (at least 128 nights per year). In those cases the normal formula operates using both parents’ incomes and the level of care.
Authority and Method
This calculator applies the legislated child support formula used for Services Australia administrative assessments and has operated continuously since 2017. Both the calculator and the guidance around it reflect how the statutory rules are applied in practice.
Child Support Australia has spent close to a decade helping parents work through real child support issues, responding to thousands of individual questions about income, care arrangements, thresholds, and outcomes. That experience informs how this calculator is designed and how the guidance below is written, focusing on the information parents actually need to enter correctly and understand clearly.
How to Use the Calculator Correctly
The sections below explain each input used in the calculation, how it is applied under the formula, and how to interpret the results. Important contextual details are included where they affect real assessments but are not obvious from the calculation alone.
How the calculation works
The calculator applies the formula set out in the Child Support (Assessment) Act 1989, using both parents’ taxable incomes, the number and ages of children, and care measured in nights per fortnight. It also applies the Australian Government’s Costs of Children Table and relevant statutory rates.
The guide below explains each input and the results in plain English.
Your taxable income
Enter your annual taxable income. Services Australia will usually base child support on the most recent income it has on record, typically from your last tax return. If your income has changed, you can submit an income estimate, and Services Australia may assess child support using that current figure instead.
For most parents, taxable income is broadly their salary. However, adjustments apply. Salary-sacrificed superannuation is added back when calculating child support, so reducing taxable income through super contributions does not reduce child support over time. Delaying a tax return to affect the assessment also does not work, as higher income is commonly backdated once lodged.
Other parent’s income
Enter the other parent’s annual taxable income. Services Australia generally uses the most recent income it has on record for each parent, usually from the last lodged tax return. If the other parent has provided an income estimate, that current figure may be used instead.
As with your own income, this is taxable income rather than take-home pay, and salary-sacrificed superannuation is added back. If the other parent’s income changes and is later updated, Services Australia may reassess child support and apply adjustments retrospectively.
Young children (0–12 years)
Enter the number of children aged 0 to 12 covered by this assessment. The child support formula applies different cost assumptions by age, using the Australian Government’s Costs of Children Table.
Younger children attract a lower cost loading in the formula than teenagers, reflecting average differences in expenses as children get older.
Teenagers (13–17 years)
Enter the number of children aged 13 to 17. Under the child support formula, teenagers attract a higher cost loading, reflecting higher average living and education expenses.
Child support generally applies until a child turns 18. In limited circumstances, support can continue beyond 18 if a child is still completing Year 12 and a parent applies for an extension.
Your care (nights per fortnight)
Enter the number of nights the child or children are in your care in a typical fortnight. Child support calculates care as a percentage, but that percentage is derived from a fortnightly overnight pattern, which is the most common way care arrangements are structured.
If you already know your care percentage, it can be converted to nights by applying it to a 14-night period. For example, 50% care corresponds to 7 nights per fortnight.
Interpreting your results
This calculator shows the annual child support assessment produced by the statutory formula, along with the equivalent monthly amount. Services Australia determines child support on an annual basis, but payments are typically made or received monthly, by calendar month.
In most cases, the parent with the majority of care receives child support. However, this is not automatic. Where care is shared and one parent has a significantly higher income, that parent may still be required to pay child support even if they have the majority of care.
Low income exceptions (2026)
The child support formula includes statutory minimum and fixed rates that apply automatically in low-income situations. These amounts form part of the legislated calculation and are applied by Services Australia where the relevant conditions are met.
- Minimum rate ($551 per year)
Applies where a parent has very low income and is receiving income support, unless the parent provides regular care (14% or more). - Fixed rate ($1,825 per year, per child)
Applied as part of the formula where a parent is not receiving income support, even if taxable income is low or zero. The calculator applies this fixed rate automatically when it is required.
These amounts are indexed and change over time, usually increasing slightly each year.
Housing affordability is often the next constraint after child support. This rent affordability calculator can help sense-check weekly rent after tax.
Independent Accuracy Verification
ChildSupportAustralia.com has operated a child support calculator since 2017. Over that time, we have seen how small implementation differences in income bands, care percentages, cost tables, and rounding stages can materially affect outcomes.
We conducted independent comparison testing against the Services Australia estimator and other widely used calculators to ensure this tool continues to apply the legislated formula correctly. In standard cases, it was the only non-government calculator found to reproduce identical results using the same inputs. See the full comparison
Parents rely on child support estimates for important financial planning decisions. Accuracy at this level is not optional.
Related tools
If you need help converting care arrangements into a care percentage, use the Care Percentage Calculator. This can be useful where care varies due to holidays or schedule changes.
About the Author
This calculator and accompanying guidance are maintained by Dr Andrew Lancaster (PhD, Economics, Australian National University). Since 2017, the site has provided independent, evidence-based explanations of Australia’s child support system and has responded to thousands of questions from parents navigating assessments, care arrangements, and statutory rules.