Child Support Assessment & Formula Guide Australia (2026–27)

In Australia, separated or divorced parents share a joint financial responsibility to support their dependent children. The Child Support Scheme, administered by Services Australia, uses an objective, statutory 8-step assessment formula to calculate child support transfers based on both parents' incomes, living costs, and the percentage of time each parent cares for the children.

Whether you are navigating separation, negotiating a private parenting agreement, or seeking a formal administrative assessment, this guide breaks down the statutory formula, Self-Support Amounts, Care Percentage tables, and binding child support agreements.

1. The Services Australia 8-Step Child Support Formula

Services Australia calculates child support through eight sequential statutory steps:

1. Calculate Each Parent’s Child Support Income: $\text{Child Support Income} = \text{Adjusted Taxable Income (ATI)} - \text{Self-Support Amount} - \text{Relevant Dependent Child Amount}$
2. Combine Incomes: Sum both parents' child support incomes to get the Combined Child Support Income.
3. Calculate Income Percentages: Divide each parent's child support income by the combined total.
4. Determine Care Percentage: Calculate the exact percentage of nights each parent cares for the child over the year.
5. Determine Cost Percentage: Map the care percentage to the statutory Cost Percentage table.
6. Calculate Child Support Percentage: $\text{Child Support Percentage} = \text{Income Percentage} - \text{Cost Percentage}$
7. Determine Costs of the Child: Look up the official Costs of Children Table based on combined income and children's ages (0–12 vs 13–17).
8. Final Child Support Payable: Multiply the Child Support Percentage by the Costs of the Child. If positive, that parent pays the other parent.

2. Key Thresholds: Self-Support Amount (2026–27)

To ensure parents can cover their own basic living expenses before paying child support, the formula deducts a statutory Self-Support Amount:

• Self-Support Amount (2026–27): Approximately ~$29,500 / year (indexed annually to average weekly earnings).
• If a parent earns less than the self-support amount, their child support income is $0.
• Fixed Annual Minimum Payment: Non-custodial parents earning below thresholds generally pay a statutory minimum of $520 per year ($10/week) per child.

3. Care Percentages & Cost Percentages Table

How many nights a child sleeps at your home directly affects your cost percentage:

Note: Crossing into Shared Care (at least 128 nights / 35%) provides an immediate 24%–25% cost credit, significantly reducing child support payable.

4. Binding vs Limited Child Support Agreements

Parents can formalize child support through three pathways:

1. Administrative Assessment: Services Australia calculates and collects payments automatically via employer payroll deductions.
2. Limited Child Support Agreement: A written agreement matching or exceeding the administrative assessment (does not require legal advice, valid up to 3 years).
3. Binding Child Support Agreement (BCSA): A permanent legal contract setting customized amounts (e.g. covering private school tuition); requires independent legal certificates from accredited family lawyers for both parents.

5. Calculate Your Child Support & Family Budget

Model child support transfers, care nights, and family cash flow using our free tools:

• Child Support Calculator — Calculate child support payments under the official 8-step formula.
• Family Budget Calculator — Model post-separation household living costs and shared expenses.
• Personal Budget Calculator — Create a solo household cash flow and savings plan.