Child Support Calculator Australia (2026–27)
Calculate your Australian Child Support assessment under current Services Australia formula rules. Model parental ATI incomes, care night percentages, self-support thresholds, and official Cost of Children tables for 2026–27.
1. Parents Income & Care Split
$1,394 / mo
Total annual payment: $16,729.
Formula Step Results
Parent 1 Income Share: 79.8%
Parent 1 Cost Percentage: 24.0%
Child Support Percentage: 55.8%
1. The Australian Child Support Assessment Framework (2026–27)
Child support in Australia is regulated by Services Australia under the Child Support (Assessment) Act 1989.
The 8-step formula assesses both parents' financial capacity and care contributions to ensure children receive appropriate financial support following parental separation.
2. Parental Combined Income & Care Night Benchmarks
| Combined Child Support Income | Care Night Breakdown | Cost of Children Amount | Annual Transferred Support | Payment Status |
|---|---|---|---|---|
| $80,000 Combined ATI (1 Child) | 80% Care / 20% Care | $12,400 Total Cost | $7,440 / Year Transferred | Parent B Pays Parent A |
| $120,000 Combined ATI (2 Children) | 60% Care / 40% Care | $21,800 Total Cost | $4,360 / Year Transferred | Parent B Pays Parent A (Shared Care Offset) |
| $160,000 Combined ATI (2 Children) | 50% Equal Shared Care | $26,500 Total Cost | $2,650 / Year Transferred | Higher Earner Pays Equalizer Offset |
| $220,000 Combined ATI (3 Children) | 85% Care / 15% Care | $34,200 Total Cost | $18,800 / Year Transferred | Parent B Pays Parent A |
3. The Mathematics of the 8-Step Formula & Cost Percentages
Net Annual Child Support Transferred (CS_annual) for Parent A income share (Inc_pct), cost share (Cost_pct), and Cost of Children (Cost_child) is:
Example Calculation ($120,000 Combined Income, 2 Children, Parent B 60% Income / 20% Care):
- Parent B Income Share: 60.0%.
- Parent B Cost Share (20% Care Nights = 24% Cost Share): 24.0% Cost Share.
- Net Differential: 60.0% - 24.0% = 36.0% net liability.
- Child Support Transferred = 36.0% × $21,800 Cost of Children = $7,848 / year.
4. Step-by-Step Guide to Calculating Child Support
Calculate Adjusted Taxable Income (ATI) for Both Parents
Sum taxable income, reportable super, and net rental losses minus self-support threshold.
Determine Combined Child Support Income & Income Percentages
Combine both parents’ child support incomes to find Parent A and Parent B income shares.
Determine Care Night Percentages & Cost Percentages
Calculate care nights per year for each parent to determine cost share percentages.
Apply Official Services Australia Cost of Children Table
Look up the total annual child expenditure based on combined income and number/age of children.
Subtract Cost Percentage from Income Percentage for Net Liability
Multiply net percentage difference by total child cost to determine annual payment transferred.
5. Child Support Assessment Mistakes & Checklist
Failing to Report Care Night Changes Promptly
Allowing the administrative assessment to reflect 50/50 care when actual care has shifted to 80/20, accumulating unpaid child support debts.
Making Informal Cash Payments Without Recording Receipt Proof
Handing over cash payments for school uniforms or extra care without Services Australia non-agency payment credit approval.
Delaying Tax Return Lodgment to Hide Income Increases
Failing to lodge tax returns; Services Australia will apply default indexation or re-assess past years once tax returns are lodged.
Signing Private Binding Agreements Without Independent Legal Advice
Executing private child support contracts without mandatory certificate of independent legal advice, rendering the agreement invalid.
Child Support Compliance Checklist
Annual Income Estimate Update (15% Variance Rule)
Lodge an Estimate of Income form with Services Australia if your earnings drop by 15%+.
Accurate Care Night Calendar Logging
Maintain a calendar log of actual overnight care stays to substantiate care percentage reviews.
Change of Assessment (Reason 8 Extra Costs) Review
Apply for Change of Assessment if a child has special medical or private schooling expenses.
Annual Income Tax Return Lodgment Compliance
Lodge annual tax returns promptly; unlodged returns trigger default income assessments.
6. Annual Child Support Assessment Lifecycle Timeline
Child Support Application Lodgment
Apply for Child Support administrative assessment via myGov Services Australia.
Assessment Notice Issued & Payment Setup
Receive official Child Support Assessment Notice; set up direct transfer or Employer Withholding.
Child Support Transfer & Care Logging
Transfer monthly assessment amounts; maintain accurate overnight care calendar entries.
Annual Income Tax Re-Assessment
Services Australia recalculates annual child support automatically upon ATO tax return lodgment.
Disclaimer: This Child Support calculator and guide are provided for general educational and informational planning purposes only. Services Australia 8-step formula rules, self-support thresholds, care night percentage tiers, and official Cost of Children tables reflect 2026–27 statutory guidelines. This page does not constitute formal legal or social security advice.
Charlotte Smith
Senior Personal Finance & Taxation Specialist at AussieSpot
Charlotte Smith is the lead personal finance advisor and workplace specialist at AussieSpot. Charlotte has over 12 years of experience helping Australian households build budgets, plan savings goals, and manage living costs.
Frequently Asked Questions (FAQ)
How is Australian Child Support calculated by Services Australia?
Child support is calculated using an 8-step legislative formula under the Child Support (Assessment) Act 1989. It compares both parents’ Adjusted Taxable Incomes (minus the self-support threshold), calculates income share percentages, determines care night percentages, and applies the official Cost of Children Table.
What is the Self-Support Threshold in 2026–27?
The Self-Support Threshold is a fixed dollar amount (~$28,500/yr) deducted from each parent’s ATI before calculating child support. It ensures both parents retain a basic living allowance for themselves.
How do Care Night percentages affect child support liability?
Care percentages determine your Cost Percentage in the formula: Regular Care (14%–34% nights = 24% cost share), Shared Care (35%–47% nights = 25%–50% cost share), Primary Care (53%–65% nights), and Sole Care (86%+ nights).
What is the difference between an Administrative Assessment and a Binding Child Support Agreement?
An Administrative Assessment is calculated automatically by Services Australia using formula rules. A Binding Child Support Agreement is a formal private legal contract (requiring independent legal advice for both parents) setting agreed lump-sum or recurring payments.
Can child support assessments be changed if income or care nights change?
YES! You must notify Services Australia immediately if your income changes by 15% or more, or if actual care night arrangements change, to trigger an updated assessment.