Child support is one of the biggest concerns separated parents face. Who pays what, how much, and why? In Australia, child support is mostly managed by Services Australia (Child Support Agency) using a set formula. This formula is designed to share the costs of raising children fairly, but many parents find it confusing or even unfair in practice.

This article explains, in plain English, how the formula works, what it considers, and why your child support might change when your income or care arrangements shift.

The Three Key Factors in Child Support Calculations

Child support is based on three main factors:

1. Each parent’s income – how much money they earn before tax.

2. The number and age of children – costs rise as children get older.

3. The care each parent provides – mainly measured by overnight stays.

Services Australia combines these factors to decide who should pay, and how much.

Step 1: Income Assessment

The starting point is each parent’s taxable income. A portion is deducted to allow for personal living expenses (so no parent is expected to hand over everything they earn).

The higher a parent’s income compared to the other, the greater their likely contribution.

Example:

• Jane earns $90,000 per year.

• Tom earns $40,000 per year.

• Because Jane earns more, she is assessed as having the greater financial capacity.

If the children live mostly with Tom, Jane will pay Tom child support.

Step 2: Care Percentages

The formula looks closely at care levels. Care is usually measured in nights per year.

• 0–13% care → considered no regular care.

• 14–34% care → regular care.

• 35–65% care → shared care.

• 66–86% care → primary care.

• 87–100% care → full care.

Even a small change in nights can shift your payments.

Example:
If a father has his children 1 night per week (14%), he will still pay a high level of child support.
If he increases this to 2 nights per week (28%), his contribution may drop because he is covering more direct costs while the children are with him.

Step 3: Costs of Children

The formula uses government research on the average costs of raising children in Australia, depending on family income and the children’s ages. Teenagers, for example, are considered more expensive than toddlers.

These costs are then split between the parents based on income and care.

Why Child Support Often Feels Unfair

Many parents argue the formula doesn’t always reflect reality. For instance:

• A parent might cover large costs (school fees, medical expenses) that the formula doesn’t consider.

• One parent might deliberately reduce their income (by working fewer hours or hiding money) to lower their payments.

• Parents who share care equally may still find the balance unfair if one parent doesn’t contribute to extra costs.

In these cases, parents can apply for a change of assessment or make their own child support agreement.

Key Takeaway

Child support is not one-size-fits-all. While the formula provides a starting point, it may not always match real family needs. Understanding how income, care, and children’s costs interact can help you prepare, negotiate, or challenge an assessment if necessary.