The Guides to Social Policy Law is a collection of publications designed to assist decision makers administering social policy law. The information contained in this publication is intended only as a guide to relevant legislation/policy. The information is accurate as at the date listed at the bottom of the page, but may be subject to change. To discuss individual circumstances please contact Services Australia.

2.4.3 The steps involved in making a child support assessment


The Registrar must follow specified steps when making an administrative assessment of child support.

An example of the calculation of an assessment using the basic formula is included at 2.4.7, where Formula 1 is explained.

There are additional steps required when one of the other 5 formulas is used. Information about these additional steps is included in:

  • 2.4.8 for cases where there is a non-parent carer in a single child support assessment
  • 2.4.9 where at least one parent has multiple child support cases, and
  • 2.4.10 where the income of one parent only is used in the assessment.

Act reference

CSA Act section 5, Part 5


When working out the annual rate of child support payable for a child using Formula 1, the basic formula, the Registrar must use the following steps:

Step Action More detail
1 Work out each parent's child support income (CSA Act section 41) 2.4.4
2 Work out the parents' combined child support income (CSA Act section 42) 2.4.7
3 Work out each parent's income percentage (CSA Act section 55B) 2.4.7
4 Work out each parent's percentage of care for the child (CSA Act section 48) 2.4.5
5 Work out each parent's cost percentage for the child (CSA Act section 55C) 2.4.5
6 Work out each parent's child support percentage for the child (CSA Act section 55D) 2.4.5
7 Work out the costs of the child under sections 55G and 55H of the CSA Act 2.4.6
8 If a parent has a positive child support percentage under Step 6, the 'annual rate of child support' payable by the parent for the child for the day is worked out using the formula:
  • Child support percentage √ó Costs of the child

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