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 Grounds for Change of Assessment

Ground 1 — Special Needs of the Child

The child has special needs — such as a disability, chronic illness, or learning difficulties — that result in significantly higher costs than the formula accounts for.

Ground 2 — High Contact Costs

The paying parent has unusually high costs to maintain contact with the child. This typically applies when parents live far apart and significant flights or accommodation costs are required.

Ground 3 — Financial Commitments That Reduce Capacity to Support

A parent has necessary financial commitments that reduce their ability to support the child — for example, caring for another dependent, or servicing debts that existed before the separation.

Ground 4 — Income Doesn't Reflect True Capacity to Earn

If Services Australia believes a parent is voluntarily under-employed or unemployed, they can impute an income based on what that parent could reasonably earn. This prevents a parent from reducing their liability by working fewer hours.

Ground 5 — Child Support Income Includes Non-Recurring Income

A parent's income in the assessment year was inflated by a one-off payment that won't recur — for example, a redundancy payout, an inheritance, or a large bonus.

Ground 6 — Property, Assets or Financial Resources Not Reflected in Income

A parent has significant assets, property, or access to financial resources that don't appear in their taxable income. Services Australia can attribute a return on those assets as additional income for assessment purposes.

Ground 7 — Income Reduced Due to Supporting a New Child

Having children in a new relationship reduces a parent's financial capacity. In some cases a formal COA on this ground provides more appropriate relief than the standard formula.

Ground 8 — Child Has Ongoing Financial Needs Requiring Support

Focused on extraordinary ongoing costs for the child — for example, ongoing expensive medical treatment not covered by the PBS.

Ground 9 — High Costs to Maintain a Meaningful Relationship

The broader financial burden on a paying parent of maintaining a real relationship with their child across distance or difficult circumstances.

Ground 10 — It Would Be Unjust Not to Change

The catch-all ground. If a parent believes the assessment is producing a genuinely unjust result and none of the other nine grounds precisely fit, Ground 10 allows a broader equity argument. It requires strong justification.

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 Appeals Tribunal (AAT)

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?

• Ground 4 (underemployment): industry salary data, previous tax returns showing higher income, recent job advertisements
• Ground 6 (hidden assets): property records, company financial statements, trust deeds
• Ground 1 or 8 (special needs): medical reports, therapy invoices, school support plans
• Ground 2 (contact costs): flight records, accommodation receipts, travel invoices

What if the Other Parent Is Hiding Income?

Grounds 4 and 6 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, Ground 6 allows those retained profits or company assets to be considered. If a parent is working cash-in-hand, Ground 4 allows Services Australia to assess what they could reasonably earn.

Change of Assessment vs Private Agreement