Multi-case allowance

The multi-case allowance reduces your income in a child support case when you also support children in another case. It recognises that your income is shared across families.

The adjustment lowers the income used in the formula for each case. The effect is often smaller than expected because it operates on income and only indirectly impacts payments.

Definition

The multi-case allowance is a component of child support income which is deducted from a parent’s adjusted taxable income when they have more than one child support case. The multi-case allowance recognises the parent’s responsibility to financially support a child or children in another child support case.

Definition source: Guides to Social Policy Law, Child Support Guide, Multi-case allowance.

Role in the formula

The multi-case allowance adjusts a parent’s income before the child support formula is applied. It sits alongside the self-support amount and any relevant dependent child amount. Only the costs of children in other cases are deducted. The current case is excluded.

Adjusted child support income
Child support income = ATI − self-support amount − relevant dependent child amount − multi-case allowance

The allowance is based on estimated costs of children in other cases using the parent’s income and the Costs of Children Table. For each child, the formula assumes all children are the same age as that child, calculates a total cost, then divides it across the children. The costs for children in other cases are then added together to form the deduction.

The adjusted income is then used in the standard formula to work out income percentages and final payments. A lower income figure can reduce what a parent pays or increase what they receive, but the change is usually moderate rather than large.

Example

Man and woman standing near a red ATM while children peek from behind it and run across a grassy field with an industrial background

A parent has taxable income of $100,000 and two child support cases. One case has 1 young child. The other case has 2 children, with one young child and a teen. The parent’s adjusted income is different for each case because the allowance only counts children in the other case.

Case with 1 child: The other case has 2 children. Multi-case allowance: $13,412. Adjusted income: $86,588.

Case with 2 children: The other case has 1 child. Multi-case allowance: $6,131. Adjusted income: $93,869.

More children in the other case create a larger deduction. Fewer children in the other case create a smaller deduction. The same parent can therefore have different income figures across child support cases.

Jimmy Barnes example (how multiple cases would work)

Jimmy Barnes standing with Jane Mahoney and daughter Mahalia Barnes smiling together in an outdoor setting

Rocker Jimmy Barnes is believed to have eight children in total. Four are from earlier relationships and four are with his wife Jane. There is no evidence that child support was formally involved in any of these situations. Let’s look at this fictional potential example since it provides a good illustration of how the multi-case allowance works.

If the modern formula were applied, the structure could look like this:

  • 4 children from earlier relationships → likely 4 separate child support cases (one per child)
  • 4 children with his wife → treated as relevant dependent children (not separate cases)

Each case would be assessed separately using a multi-case allowance:

  • Each case: The formula would include the other 3 children potentially involved in child support when calculating the allowance.
  • Result: The deduction would be similar across cases because each one accounts for 3 other children.
  • Variation: Differences would mainly come from the ages of those children, particularly whether they fall into the 0–12 or 13–17 group.

The four children in his household reduce income through the relevant dependent child amount, which is a separate step and applies across all cases.