The calculator uses the same formula and the same cost-of-children tables as Services Australia's own estimator. The self-support amount is updated to $31,046 for 2026. For most straightforward situations, the result will be very close to your formal assessment.
It won't account for every variable in complex situations — a Change of Assessment, a binding private agreement, or special circumstances can all change the final figure. But for a reliable starting point, this is the fastest way to understand what you're looking at.
Services Australia uses an 8-step formula introduced under the Child Support (Assessment) Act 1989.
| Step | What it calculates |
|---|---|
| 1 | Each parent's Adjusted Taxable Income (ATI) |
| 2 | Subtract the self-support amount ($31,046 in 2026) to get Child Support Income |
| 3 | Add both parents' Child Support Incomes together |
| 4 | Calculate each parent's percentage of the combined income |
| 5 | Apply the costs-of-children table to get the total annual child costs |
| 6 | Apportion those costs between parents based on income percentage |
| 7 | Apply a care cost offset based on how much time each parent spends with the children |
| 8 | Calculate the final transfer amount — what one parent pays the other |
For a full walkthrough of the formula with worked examples, see our guide: How is child support calculated in Australia.
The self-support amount for 2026 is $31,046. The costs-of-children tables are updated each year.
| Combined Income (both parents) | 1 Child (annual) | 2 Children (annual) | 3 Children (annual) |
|---|---|---|---|
| $40,000 | ~$5,800 | ~$8,700 | ~$10,400 |
| $70,000 | ~$9,200 | ~$13,800 | ~$16,600 |
| $100,000 | ~$12,400 | ~$18,600 | ~$22,300 |
| $130,000 | ~$14,900 | ~$22,400 | ~$26,800 |
| $160,000+ | ~$17,100 | ~$25,700 | ~$30,800 |
Note: These are illustrative figures. Your actual assessment depends on exact combined income and care percentage.
The child support formula is national — identical in every state. For local resources and legal aid contacts, see:
Set up a private agreement — either a Limited Agreement (no lawyers needed) or a Binding Child Support Agreement (more flexible, lawyers required).
Apply for a formal child support assessment through myGov. Services Australia will calculate the official amount, notify both parents, and collect and transfer payments on your behalf.
A Change of Assessment allows either parent to apply to depart from the formula on specific grounds.
Your assessment updates automatically each year when tax returns are lodged. If your income changes by more than 15% during the year, apply for a reassessment promptly.
Yes. The self-support amount for 2026 is $31,046, updated annually by Services Australia.
Yes. Enter the number of nights per fortnight each parent has the children. The calculator applies the care cost offset automatically.
You can enter an estimated figure to get a rough idea. For a formal assessment, Services Australia will obtain the other parent's income from the ATO directly.
It's an estimate using the same formula and tables. Differences can arise from special circumstances, a Change of Assessment, or non-standard income components.
Use your adjusted taxable income as reported to the ATO. If Services Australia believes your declared income understates your earning capacity, they can apply a notional income.