2.4.9 Assessments when a Parent Has Multiple Child Support Cases (Formulas 3 & 4)

Context

Formula 3 is used to calculate the child support assessment when one or both parents have more than one child support case.

If somebody other than a parent is providing some care for a child and one or both parents have multiple child support cases then formula 4 is used to calculate the assessment for that case.

Act references

CSA Act section 36 to section 38, section 41, section 42, section 46 to section 48, section 55A to section 55E, section 55HA, section 156

On this page

Parents can have more than one child support case, that is, they can have children from different relationships in child support assessments with more than one other parent. To recognise a parent's responsibility to support their children in another child support case, one of two separate mechanisms is used. These mechanisms are:

  • the multi-case allowance, which is deducted from a parent's adjusted taxable income to reach their child support income at step 1 of the basic formula (CSA Act section 47); and
  • the multi-case cap which is a separate calculation for the paying parent worked out at step 8 (section 55E).

For each child, the lesser of the 2 amounts calculated will be the assessed rate of child support. Only one mechanism functions at a time - either the child support is worked out using the income after the deduction of the multi-case allowance, or the child support is worked out according to the multi-case cap on child support.

Multi-case child costs

Both the multi-case cap and the multi-case allowance are calculated using the multi-case costs of the children. The multi-case costs of a child are what it would cost the parent to support the child if all of the children lived with them, based on that parent's income. When calculating the multi-case costs, use the parent's adjusted taxable income less the self-support amount and less the relevant dependent child amount (where appropriate).

To calculate the multi-case child costs of a 'particular child' determine what the costs of all the parent's child support children would be if they were all the same age as this child and divide the costs by the number of child support children.

Note: 'all child support children' are all of the parent's children in the child support assessments of the parent for whom you are calculating the multi-case costs.

The approach used to calculate the multi-case costs of a child, although similar, differs from the multiple case method (2.4.6) of calculating the costs of a child. This is because the multi-case costs recognise a parent's responsibility for all their children in all their child support cases, whereas the multiple case method calculates a parent's child support responsibility for the child or children in a case.

Example: M has an initial child support income of $20,000 (the adjusted taxable income less the self-support amount). M and F1 have 2 children, A aged 14 and B aged 10. M has another child support case with F2 for child C, aged 5. The multi-case child costs for A and B would be:

Costs of A (14 years old)
=$20,000 × $0.32 (3+ children aged 13+ years from the costs of children tables)
=$6,400 ÷ 3 (divide by number of all child support children)
=$2,133

Costs of B (10 years old)
=$20,000 × $0.27 (3+ children aged 0 - 12 years from the costs of children tables)
=$5,400 ÷ 3 (divide by number of all child support children)
=$1,800

Multi-case allowance

The multi-case allowance is an allowance deducted from a parent's adjusted taxable income to recognise a parent's responsibility for child support for their children in another child support case (CSA Act section 47).

The multi-case allowance is the sum of the multi-case child costs, excluding the costs of the children of the case to which the assessment relates. That is, the parent has an amount deducted from their income to recognise the costs of supporting the children in their other case or cases. The amount deducted is the total of the multi-case costs of those other children.

Example: F has children from 3 relationships. F and M1 have 2 children, A and B. F and M2 have one child, C. M2 also has an assessment with W for their children, Y and Z. F and M3 have 2 children, D and E.

In calculating F's child support income for the assessment for A and B, the multi-case allowance is the multi-case costs of C, D and E.

In calculating F's child support income for the assessment for C, the multi-case allowance is the multi-case costs of A, B, D and E. M2 will also have a multi-case allowance, being the multi-case costs of Y and Z.

In calculating F's child support income for the assessment for D and E, the multi-case allowance is the multi-case costs of A, B and C.

A parent can meet the costs of each child by paying child support, by directly caring for the child or by a combination of the 2. Therefore the multi-case allowance recognises the costs of a child in another case, not the amount of child support payable.

The multi-case allowance is rounded to the nearest dollar (CSA Act section 156).

Example: M has an initial child support income of $20,000 (the adjusted taxable income less the self-support amount). M has no relevant dependent children. M and F1 have 2 children, A aged 14 and B aged 10. M has another child support case with F2 for child C, aged 5. In calculating the assessment for C, the multi-case allowance for A and B is the total of the multi-case costs for A and B. The costs are as calculated in the example above.

Child support income for M

Multi-case allowance = multi-case costs of A + B
=$2,133 + $1,800
=$3,933

Initial child support income less the multi-case allowance
=$20,000 − $3,933
=$16,067

Multi-case cap

The multi-case cap is used to ensure that the parent does not pay more child support for a child than they would if all the children lived in the same household. The cap recognises that the parent may be bearing some of the costs of a child directly through regular or shared care, and is adjusted accordingly. The cap is calculated on a per child basis.

The multi-case cap for each child is the multi-case child costs for the child, less the costs that the parent meets directly through care (their cost percentage).That is:

(100% − cost percentage) × multi-case child costs.

Example: If M has regular care of child B, and therefore a cost percentage of 24% for B, and B's multi-case child cost is $1,800, then:

Multi-case cap = (100%-24%) × $1,800
= 76% × $1,800 = $1,368

Multi-case allowance or multi-case cap

The multi-case allowance recognises a parent's responsibility to their other child support children by using an income shares approach. The multi-case cap ensures a parent does not pay more for a child than they would if all children were living in the one household. Both the cap and the allowance are methods of recognising the parent's other obligations, so only one method is needed at any one time.

Only one method will be used to determine the child support amount payable for each child i.e. either the child support amount is worked out using the income after the deduction of the multi-case allowance, or the child support is worked out according to the cap. For each child, the lesser of the 2 amounts calculated will be the assessed rate of child support.

Formula 3 - Parents in multiple child support cases

When one or both of the parents have at least one other case, and there is no non-parent carer, some variations are made to the basic formula steps to work out the annual rate of child support payable for a child (CSA Act section 36). Additional or changed calculations are made at steps 1, 4, 5, 7 and 8 as explained below.

Step 1: To work out each parent's child support income (2.4.7) (section 41), first identify their interim child support income, which is their adjusted taxable income less the self-support amount. Using that income, work out a relevant dependent child (2.4.6) amount (section 46), if required. Deduct that amount from the interim child support income. Then use the interim child support income (less the relevant dependent amount, as required) to calculate the multi-case allowance for each parent with more than one case (section 47). The parent's child support income is their adjusted taxable income less the self-support amount, less any relevant dependent child amounts, and less any relevant multi-case allowance.

Step 2: Work out the parents' combined child support income (2.4.7) (section 42).

Step 3: Work out each parent's income percentage (2.4.7) (section 55B).

Step 4: Work out each parent's percentage of care (2.4.5) for the child (section 48).

Step 5: Work out each parent's cost percentage (2.4.5) for the child (section 55C).

Step 6: Work out each parent's child support percentage (2.4.5) for the child (section 55D).

Step 7: Work out the costs of the child (2.4.6) for the day under section 55HA, calculating the costs for older and younger children separately.

Step 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 is worked out using the formula:

Child support percentage × cost of the child

The outcome of step 8 will be the child support payable if the parent assessed to transfer child support does not have more than one child support case.

If a parent has more than one child support case and a positive child support percentage under step 6, calculate the multi-case cap for that parent (section 55E):

Multi-case cap =
(100% − Parent's cost percentage (2.4.5) for the particular child) × Multi-case child costs for the particular child

The child support payable for the child is the lower of the amounts calculated at step 8, or the multi-case cap.

Example: Formula 3 calculations

M and F1 have 2 children, A aged 14 and B aged 10. M has another child support case with F2 for child C, aged 5. M has an adjusted taxable income of $45,000 and F2 has an adjusted taxable income of $40,000. Calculate the assessment for C, who lives mostly with F2, for a child support period commencing on 26 August 2008. M has regular care of C, providing care for 75 nights a year. Neither parent has any relevant dependent children.

Step 1: Work out each parent's child support income by deducting the self-support amount and a multi-case allowance for any parent with multiple cases from their adjusted taxable income.

Child support income for M

Initial child support income = adjusted taxable income − self-support amount
$45,000 − $18,252
= $26,748

Multi-case costs
Costs of A (older child):
=$26,748 × $0.32 (3+ children aged 13+ years from the 2008 costs of children table)
=$8,559 ÷ 3 (divide by number of all child support children)
=$2,853

Costs of B (younger child):
=$26,748 × $0.27 (3+ children aged 0 - 12 years from the 2008 costs of children table)
=$7,222 ÷ 3 (divide by number of all child support children)
=$2,407

Multi-case allowance = multi-case costs of A + B
= $2,853 + $2,407
= $5,260

M's child support income = initial child support income − multi-case allowance
= $26,748 − $5,260
= $21,488

F2 has a child support income of $21,748 ($40,000 − $18,252).

Step 2: Work out the parents' combined child support income.

$21,488 + $21,748 = $43,236

Step 3: Work out each parent's income percentage.

M = $21,488 ÷ $43,236 × 100 = 49.70%

F2 = $21,748 ÷ $43,236 × 100 = 50.30%

Step 4: Work out each parent's percentage of care for each child.

M has care of C for 75 nights = 20.55%, rounded to a percentage of care of 20%.

F2 has care of C for 290 nights = 79.45%, rounded to a percentage of care of 80%.

Step 5: Work out each parent's cost percentage for each child by looking up the table in section 55C.

M has a cost percentage of 24%.

F2 has a cost percentage of 76%.

Step 6: Work out each parent's child support percentage by subtracting their cost percentage for that child from their income percentage.

M = 49.70% − 24% = 25.70%

F2 = 50.30% − 76% = −25.70%

(This means that M is responsible for 49.70% of C's costs because they have 49.70% of the combined child support income. As M meets only 24% of the costs through care they need to transfer 25.70% of the costs to F2 through child support.)

Step 7: Work out the costs of each child.

The combined child support income is $43,236.

From the 2008 costs of children table, the total costs of the child (one child 12 or under) =

$4,654 + ($0.15 for every $1 over $27,378)

$4,654 + ($43,236 − $27,378 = $15,858 × $0.15 = $2,379)

Therefore: $4,654 + $2,379= $7,033

The cost of each child = $7,033.

Step 8: Work out the annual rate of child support payable by the parent with a positive child support percentage.

25.70% × $7,033= $1,807

OR use the multi-case cap.

Multi-case cap = (100% − parent's cost percentage for the particular child) × multi-case child costs for the particular child
= (100% − 24%) × $2,407
= 76% × $2,407
=$1,829

As the amount calculated at step 8 ($1,807) is less than the multi-case cap ($1,829), the step 8 amount should be paid.

M is liable to pay F2 child support for C of $1,807 (annual rate).

Formula 4 - Multiple child support cases with a non-parent carer

When one or both of the parents have at least one other case, and one or more non-parent carers has at least 35% percent of care for a child, variations are made to the basic formula steps to work out the annual rate of child support payable for a child (CSA Act section 38). Additional or changed calculations are made at steps 1, 4, 5, 7 and 8 as explained below.

Step 1: To work out each parent's child support income (section 41), first identify their interim child support income, which is their adjusted taxable income less the self-support amount. Using that income, work out a relevant dependent child (2.4.6) amount (section 46), if required. Deduct that amount from their interim child support income. Then use the interim child support income (less the relevant dependent amount, as required) to calculate the multi-case allowance for each parent with more than one case (section 47). The parent's child support income, then, is their adjusted taxable income less the self-support amount, less any relevant dependent child amounts, and less any relevant multi-case allowance.

Step 2: Work out the parents' combined child support income (2.4.7) (section 42).

Step 3: Work out each parent's income percentage (2.4.7) (section 55B).

Step 4: Work out each parent's and non-parent carer's percentage of care (2.4.5) for the child (section 48).

Step 5: Work out each parent's and non-parent carer's cost percentage (2.4.5) for the child (section 55C).

Step 6: Work out each parent's child support percentage (2.4.5) for the child (section 55D).

Step 7: Work out the costs of the child (2.4.6) for the day under section 55HA, calculating the costs for older and younger children separately.

Step 8: If a parent has a positive child support percentage under step 7, 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 × cost of the child

The outcome of step 8 will be the child support payable if the parent assessed to transfer child support does not have more than one child support case.

If a parent has more than one child support case and a positive child support percentage under step 6, calculate the multi-case cap for that parent (section 55E):

Multi-case cap =
(100% − parent's cost percentage (2.4.5) for the particular child) × multi-case child costs for the particular child

The child support payable is the lower of the amount calculated at step 8 or the multi-case cap.

Example: Formula 4 calculations

F and M1 have 2 children, A aged 14 and B aged 10. F has another child support case with M2 for child C, aged 7. F also has another child D, aged 4, living with them. There is no assessment for D. F has an adjusted taxable income of $45,000 and M1 has an adjusted taxable income of $70,000.

Calculate the assessment for A and B for a child support period commencing on 26 August 2008. A lives full time with M1 and B lives full time with a grandparent G. G has made an application under section 25A for a child support assessment.

Step 1: Work out each parent's child support income by deducting the self-support amount, relevant dependent amount (as required) and a multi-case allowance for any parent with multiple cases from their adjusted taxable income.

Child support income for F

Initial child support income = adjusted taxable income − self-support amount
= $45,000 − $18,252 = $26,748

Relevant dependent allowance for D

Costs of D (younger child):
= $26,748 × $0.17 (1 child aged 0-12 years from the 2008 costs of children table)
= $4,547

Initial child support income for this case = adjusted taxable income − self-support amount − relevant dependent allowance
= $45,000 − $18,252 − $4,547 = $22,201

Multi-case costs

Costs of older child:
= $22,201 × $0.32 (3+ children aged 13+ years from the 2008 costs of children table)
= $7,104 ÷ 3 (divide by number of all child support children)
= $2,368

Costs of younger child:
= $22,201 × $0.27 (3+ children aged 0-12 years from the 2008 costs of children table)
= $5,994 ÷ 3 (divide by number of all child support children)
= $1,998

Multi-case allowance = multi-case costs of C (younger child)
= $1,998

Child support income = initial child support income (this case) − multi-case allowance
= $22,201 − $1,998
= $20,203

F has a child support income of $20,203.

M1 has a child support income of $51,748 ($70,000 − $18,252).

Step 2: Work out the parents' combined child support income.

$20,203+ $51,748 = $71,951.

Step 3: Work out each parent's income percentage.

F = $20,203 ÷ $71,951 × 100 = 28.08%

M1 = $51,748 ÷ $71,951 × 100 = 71.92%

Step 4: Work out each parent's percentage of care for each child.

F has 0% care of A.

M1 has 100% care of A.

F has 0% care of B.

M1 has 0% care of B.

(G has 100% care of B.)

Step 5: Work out each parent's cost percentage for each child by looking up the table in section 55C.

F has a cost percentage of 0% for both A and B.

M1 has a cost percentage of 100% for A.

M1 has a cost percentage of 0% for B.

Step 6: Work out each parent's child support percentage by subtracting their cost percentage for that child from their income percentage.

F = 28.08% − 0% = 28.08% for both A and B

M1 for A = 71.92% − 100% = −28.08%

M1 for B = 71.92% − 0% = 71.92%

(This means that F is responsible for 28.08% of the costs of A and B because they have 28.08% of the combined child support income. As F does not meet any of the costs through care they need to transfer 28.08% of the costs to the carers through child support. M1 is entitled to receive child support from F for A and is required to pay child support for B.)

Step 7: Work out the costs of each child.

The combined child support income is $71,951.

Costs of A (older child):

$15,606 + ($0.25 for every $1 over $54,756) (2 children aged 13+ years from the 2008 costs of children table)

= $15,606 + ($71,951 − $54,756 = $17,195 × $0.25 = $4,299)
= $15,606 + $4,299 = $19,905
= $19,905 ÷ 2
= $9,953

Costs of B (younger child):

$12,868 + ($0.20 for every $1 over $54,756) (2 children aged 12 years or under from the 2008 costs of children table)

= $12,868 + ($71,951 − $54,756 = $17,195 × $0.20 = $3,439)
= $12,868 + $3,439= $16,307.
= $16,307 ÷ 2
= $8,154

Step 8: Work out the annual rate of child support payable by the parent with a positive child support percentage.

Annual Rate payable for A

F is to pay M1: 28.08 % × $9,953= $2,795

OR

Multi-case cap = (100% − parent's cost percentage for the particular child) × multi-case child costs for the particular child
= (100% − 0%) × $2,368
= 100% × $2,368
= $2,368

As the amount calculated at step 8 ($2,795) is more than the multi-case cap ($2,368) the multi-case cap should be paid.

F is liable to pay M1 child support for A of $2,368 (multi-case cap).

Annual Rate payable for B

Both F and M1 have positive child support percentages for B and therefore both are required to pay child support to G.

F is to pay G: 28.08 % × $8,154= $2,290

OR

Multi-case cap = (100% − parent's cost percentage for the particular child) × multi-case child costs for the particular child
= (100%-0%) × $1,998
= 100% × $1,998
= $1,998

As the multi-case cap ($1,998) is less than the amount calculated at step 8 ($2,290) then the multi-case cap should be paid.

F is liable to pay M1 child support for A of $1,998 (annual rate).

M1 is to pay G: 71.92% × $8,154= $5,864

G is entitled to receive $1,998 + $5,864 = $7,862

When child support is payable by or to more than one person

If both parents have a positive child support percentage at step 6 of the formula calculations then both parents pay child support to the non-parent carer or carers (CSA Act section 38(5)).

Example: The first parent, M, has a child support percentage of 83.47%.

The second parent, F, has a child support percentage of 16.53%.
The costs of the child are $1,000.

Both parents are required to pay child support to G, who has full-time care of the child.
M will pay $1,000 × 83.47% = $835.
F will pay $1,000 × 16.53% = $165.

If one parent, the first parent, has a positive child support percentage at step 6 and the other parent has:

  • a negative child support percentage, and
  • less than shared care

then the first parent pays child support to the non-parent carer or carers (section 38(5)).

Example: The first parent, M, has a child support percentage of 83.47%.
The second parent, F, has regular care of the child and a child support percentage of −7.47% (16.53% − 24%).
The costs of the child are $1,000.

The first parent is required to pay child support to G, who has primary care of the child.
M will pay $1,000 × 83.47% = $835.

If one parent, the first parent, has a positive child support percentage at step 6 and the other parent has:

  • a negative child support percentage, and
  • at least shared care

then the first parent pays child support to the second parent and the non-parent carer (section 38(6)). The child support payable will be divided between the second parent and the non-parent carer by calculating their respective cost percentage as a proportion of their combined cost percentage.

Example: The first parent, M, has a child support percentage of 83.47%.
The second parent F, has 37% care of the child (shared care) which is a cost percentage of 29% and a child support percentage of −12.47% (16.53% − 29%).

The non-parent carer, G, has 49% care of the child (shared care) which is a cost percentage of 50%.
The costs of the child are $1,000.

M is liable to pay $1,000 × 83.47% = $835 in total.

M is required to pay child support to F, using F's cost percentage divided by the combined cost percentages of F and G.
M will pay 835 × 29% ÷ (29% + 50%) = $307 to F.
M is required to pay child support to G using G's cost percentage divided by the combined cost percentages of G and F.
M will pay 835 × 50% ÷ (29% + 50%) = $528 to G.

A non-parent carer is not entitled to be paid child support unless they have at least 35% care of the child and they have applied under section 25A (section 40B). If more than one non-parent carer is entitled to receive child support from a parent or both parents, then their share of the entitlement is determined in accordance with section 40A. See 2.4.8 for information about the calculations required when child support is payable to more than one person.

Different rules apply if the minimum annual rate of child support is payable to more than one person. See 2.4.12 for details of the rules that apply, which depend upon the level of care provided by the carer.

Last reviewed: 11 May 2015