Change of Assessment Child Support Australia [2026 Guide]

The child support formula works for most families. But not every situation fits the standard calculation — and that's exactly what the Change of Assessment process exists for. If your circumstances mean the formula produces an unfair result, either parent can apply to Services Australia to depart from it.

What is a Change of Assessment?

The standard formula is a starting point. It's accurate and fair for typical circumstances — two parents with regular income and a straightforward care arrangement. But many families don't fit that template.

A Change of Assessment is the formal mechanism that allows either parent to present their circumstances to Services Australia and ask for the assessment to be adjusted. Services Australia must assess whether changing the assessment is just and equitable — to both parents and to the child.

Who Can Apply?

Either the paying parent or the receiving parent can apply. You don't need legal representation, though complex cases often benefit from it.

The 10 Reasons for Change of Assessment

Services Australia uses the official Child Support Guide numbering. Reason 8 has two sub-parts, 8A and 8B, so you will often see 11 listed items even though the legislation still refers to 10 reasons overall.

Reason 1 — High costs of enabling a parent to spend time with or communicate with the child

Applies where those costs exceed 5% of the parent's adjustable taxable income.

Reason 2 — High costs associated with the child's special needs

This includes costs arising from a physical, mental or learning disability, or a special talent.

Reason 3 — High costs of caring for, educating or training the child in the way both parents intended

This reason focuses on costs both parents intended the child to have, such as particular schooling, training or other established arrangements.

Reason 4 — The assessment is unfair because of the child's income, earning capacity, property or financial resources

This reason looks at the child's own financial position, not the parents' financial position.

Reason 5 — The assessment is unfair because the paying parent has already paid or transferred money, goods or property for the child's benefit

This can include payments or transfers to the child, the receiving parent, or a third party for the child's benefit, including through a property settlement.

Reason 6 — High childcare costs for the child

The child must be under 12, and the childcare costs must exceed 5% of the child support income amount.

Reason 7 — A parent's necessary expenses significantly reduce their capacity to support the child

This reason applies where necessary expenses materially reduce what that parent can contribute.

Reason 8A — The assessment is unfair because of the income, property or financial resources of one or both parents

This covers assets or financial resources that are not properly reflected in taxable income.

Reason 8B — The assessment is unfair because of the earning capacity of one or both parents

This applies to voluntary underemployment or unemployment. Three compulsory criteria must all be met: (1) the parent is not working, is working reduced hours, or has changed occupation, industry or working pattern; (2) that decision is not justified by their caring responsibilities or state of health; and (3) the parent has not demonstrated that affecting the child support assessment was not a major purpose of that decision.

Reason 9 — A parent's capacity to support the child is significantly affected by their duty to maintain another child or person

This includes the costs of spending time with that other child or person.

Reason 10 — A parent's responsibility to maintain a resident child significantly reduces their capacity to support the child

This reason deals specifically with the impact of maintaining a resident child.

The Change of Assessment Process

1. Apply online through myGov or by calling Services Australia on 131 272
2. Services Australia contacts the other parent and gives them 28 days to respond
3. Both parents submit financial information and supporting evidence
4. A Senior Case Officer reviews all submissions
5. A decision is issued — the assessment may increase, decrease, or stay the same
6. Either parent can object to the decision within 28 days
7. If still unsatisfied, apply to the Administrative Review Tribunal (ART)

How Long Does It Take?

Typically 8–12 weeks from application to decision. The existing assessment continues during this time. If your application is successful, changes are backdated to the date you applied — not the date the decision was made. Apply promptly.

What Evidence Do You Need?

• Reason 8B (earning capacity): industry salary data, previous tax returns showing higher income, recent job advertisements
• Reason 8A (income, property or financial resources): property records, company financial statements, trust deeds
• Reason 2 (special needs): medical reports, therapy invoices, school support plans
• Reason 1 (time or communication costs): flight records, accommodation receipts, travel invoices

What if the Other Parent Is Hiding Income?

Reasons 8A and 8B specifically address this scenario. Services Australia can request income information directly from the ATO — the other parent can't simply refuse to provide it.

If a parent is a company director paying themselves a low salary while retaining profits in the company, Reason 8A allows those retained profits or company assets to be considered. If a parent is working cash-in-hand, Reason 8B allows Services Australia to assess what they could reasonably earn.

Change of Assessment vs Private Agreement