Child Support Estimator
This is a child support estimator that applies the Services Australia 8-step formula under the Child Support (Assessment) Act 1989 (Cth). Enter each parent’s adjusted taxable income, care percentage, and number of children, and it returns an indicative annual child support figure. Services Australia’s administrative assessment is the authoritative figure — use this for planning only.
What this calculator does
The Services Australia Child Support Agency calculates child support using a formula that weighs both parents’ incomes, the costs of children by age band, and each parent’s care percentage. This calculator applies the same 8-step formula so family lawyers, mediators, and parents can run scenarios before lodging an application.
Legal basis
Child support is governed by the Child Support (Assessment) Act 1989 (Cth). The 8-step administrative assessment formula sits in Part 5 of the Act. The Costs of the Children table is set out in Schedule 1. Services Australia administers assessments; review and change of assessment sit under Parts 6A–7.
How the calculation works
8-step formula: (1) each parent’s adjusted taxable income, (2) subtract self-support amount, (3) combined child support income, (4) each parent’s income percentage, (5) each parent’s care percentage (nights ÷ 365) and cost percentage, (6) each parent’s child support percentage = income % − cost %, (7) cost of the children from Schedule 1 table, (8) annual child support = payer’s child support % × cost of the children.
Interactive calculator coming soon
For two children (mixed age), Parent 1 income $90,000 with 110 nights of care and Parent 2 income $50,000 with 255 nights of care, an indicative annual child support figure payable by Parent 1 to Parent 2 is in the order of $8,000–$11,000 per year.
In the meantime, use the worked example above to validate your figures and confirm the final amount with the relevant revenue office or authority before relying on it in a matter.
Start free trialWhat you fill in
- Parent 1 adjusted taxable income (AUD) (currency): Must be a positive number
- Parent 2 adjusted taxable income (AUD) (currency): Must be a positive number
- Number of children (number): 1–6
- Parent 1 nights of care per year (number): 0–365
- Children’s age band (select): Required
Limitations
- Does not apply non-parent carer assessments
- Does not model second-family or additional-relevant-dependent-child allowances in full
- Does not handle change of assessment (Part 6A) applications or departures
- Self-support amount and costs of the children table are indexed annually — confirm current figures
- Does not address private collection, child support agreements, or court-based departure
What to do next
For the authoritative figure, lodge an assessment with Services Australia (online via myGov). For agreed arrangements, a family lawyer can draft a limited or binding child support agreement under Part 6 of the Act. Quillio supports family lawyers drafting financial disclosure and agreement summaries — see /practice-areas/family-lawyers.
Calculator FAQs
Is this the Services Australia formula?
Yes — it replicates the 8-step administrative assessment formula in Part 5 of the Child Support (Assessment) Act 1989 (Cth), using the current Costs of the Children table in Schedule 1. Services Australia’s own assessment remains authoritative.
How does care percentage affect the amount?
Care percentage (converted from nights of care) drives each parent’s cost percentage. The closer care is to 50/50, the more the cost percentage offsets the income percentage, reducing the transfer payable.
Does the age of the children matter?
Yes — the Costs of the Children table in Schedule 1 applies different cost bands for children aged 0–12 and 13–17. Mixed-age sibling groups blend the bands.
What is adjusted taxable income?
Adjusted taxable income includes taxable income plus reportable fringe benefits, reportable super contributions, net investment losses, tax-free pensions/benefits, and foreign income. It is defined in the Act.
Can parents agree on a different amount?
Yes — parents can enter a limited or binding child support agreement under Part 6 of the Act. A binding agreement requires independent legal advice. The calculator output is a useful benchmark for negotiation.
Does the estimate include spousal maintenance?
No — spousal maintenance is a separate statutory claim under the Family Law Act 1975 (Cth) and is not modelled here.
What if one parent’s income isn’t accurate?
Services Australia can apply a default income or consider a change of assessment under Part 6A in certain circumstances. That process sits outside the 8-step formula.
Get help with the matter
For family lawyers, Quillio accelerates the financial disclosure review that underpins every child support dispute — payslips, tax returns, and business financials parsed into a clean income picture. See /practice-areas/family-lawyers.
This calculator is an estimate only. Services Australia’s administrative assessment is the authoritative figure. Agreements that depart from the formula must comply with Part 6 of the Child Support (Assessment) Act 1989 (Cth) and generally require independent legal advice.
Quillio handles the next steps.
The calculator gives you the number. Quillio handles the rest of the matter — drafting, review, research, and correspondence. The free trial requires no credit card.
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