Change of Assessment (COA)
A Change of Assessment (COA) is a way to adjust a child support assessment when the formula does not properly reflect a family’s situation. Either parent can apply, and Services Australia reviews the broader financial circumstances of both sides.
A COA review is a structured administrative process that requires evidence and can affect the child support assessment.
Definition
Change of assessment is an administrative option available to parents of a child support case who believe their formula assessment does not reflect the special circumstances of their case.
The change of assessment process allows the Registrar to examine the broader financial circumstances of both parents and determine if a departure from assessment would be appropriate.
Definition source: Guides to Social Policy Law, Child Support Guide, Version 4.97, released 20 March 2026, 1.1.C.50 Change of assessment.
Role in the formula
A Change of Assessment does not replace the child support formula with a different system. It changes the result of the formula assessment where special circumstances justify a different outcome.
The Registrar can make a direct decision about the assessment itself. That can mean increasing or reducing the annual rate of child support, rather than only altering the underlying inputs. In other cases, the Registrar can change one part of the formula so the assessment recalculates on a different basis.
The Registrar can set a parent’s income at a specific level if their taxable income does not reflect their true capacity to support the child. The Registrar can also directly vary the annual rate or adjust key parts of the formula, including cost percentage, child support percentage, and the costs of the child.
A COA can produce a precise outcome. It might add a defined amount for a specific expense, reduce the assessment for a past period, or fix one parent’s income at a higher or lower level. The result depends on the reason established, the evidence provided, and whether the outcome is just and equitable and otherwise proper.
Reasons for a Change of Assessment
A COA can only be made if one or more of the following reasons is established due to special circumstances:
- Reason 1: High costs of enabling a parent to spend time with or communicate with the child.
- Reason 2: High costs associated with the child’s special needs.
- Reason 3: High costs of caring for, educating, or training the child in the way both parents expected.
- Reason 4: The assessment is unfair because of the child’s income, earning capacity, property, or financial resources.
- Reason 5: The assessment is unfair because a parent has already paid or transferred money, goods, or property for the child’s benefit.
- Reason 6: High child care costs for a child under 12.
- Reason 7: A parent’s capacity to support the child is significantly reduced due to necessary commitments to support themselves.
- Reason 8A: The assessment is unfair because of the income, property, or financial resources of one or both parents.
- Reason 8B: The assessment is unfair because of the earning capacity of one or both parents.
- Reason 9: A parent’s capacity is affected by responsibilities to support another child or person.
- Reason 10: A parent’s capacity is reduced due to responsibility for a resident child.
These reasons limit when a COA can be used. General dissatisfaction with the formula is not enough.
Example
One parent applies for a COA under Reason 2 because their child needs dental braces and the treatment is expensive. The applying parent provides a diagnosis, treatment plan and quote from an orthodontist.
Services Australia considers whether the cost is necessary and reasonable, and whether both parents can contribute.
A common outcome is to recognise the cost and effectively share it between the parents. For example, the Registrar may treat the braces as a specific additional cost and assign responsibility on an equal basis, with one parent required to pay extra child support to cover half the additional cost.
The decision depends on the evidence, the parents’ financial positions, and whether the adjustment is just and equitable.
What it means if you apply for a COA
You apply for a COA, you are asking Services Australia to look beyond the formula. This requires clear evidence of special circumstances. The process involves information gathering, submissions, and a formal decision. It is more involved than a standard update but does not require going to court.
Decisions apply for a defined period. If circumstances continue to change, further applications may be needed. Each application adds time and administrative effort for both parents.
What it means if the other parent applies
If the other parent initiates a COA, you will be asked to respond and provide your own financial information. The Registrar considers both sides before making a decision. The outcome may increase or decrease the assessment, regardless of who applied.
A COA can affect multiple parts of the calculation. Even if only one issue is raised, the Registrar may adjust other elements if the evidence supports it. The final result is based on the overall fairness of the assessment, not just the original claim.
How long a COA decision lasts
A Change of Assessment decision applies for a defined span of time. There is no fixed duration. The Registrar sets how long the decision will run based on the circumstances of the case.
If the situation is stable, the decision may be set to run for a longer time. If circumstances are likely to change, the decision may be limited to a shorter span so the assessment can be reviewed again.
The decision can also be structured to change over time if circumstances are expected to shift. The aim is to produce a workable assessment without requiring repeated applications.