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 1 or both parents have more than 1 child support case.

If somebody other than a parent is providing some care for a child and 1 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 7B, 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 1 child support case, that is, they can have children from different relationships in child support assessments with more than 1 other parent. To recognise a parent's responsibility to support their children in another child support case, 1 of the following mechanisms will be used to calculate child support assessments for parents with multiple child support cases:

  • 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 (section 47), or
  • the multi-case cap, which is a separate calculation for the paying parent worked out at step 8 (section 55E).

For each child, a child support amount will be worked out using each of these 2 mechanisms, and the lesser of the 2 amounts will be the assessed rate of child support. Only 1 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 parent's child support children lived with them full-time, based on that parent's income.

When calculating the multi-case costs, use the parent's adjusted taxable income for the child support case, less the self-support amount and less the relevant dependent child amount (where appropriate).

The multi-case cost of each child is calculated as if all the child support children were the same age as that child. To work out this cost:

  • work out the total number of the parent's child support children
  • look up the parent's (individual) income and the age of the child on the relevant Costs of the Children Table (2.4.2) to find what all the children would cost if they were all the same age
  • divide this amount by the total number of the parent's child support children.

Note: 'The parent's child support children' are all of the children currently 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: Jonah has an initial child support income of $20,000 (the adjusted taxable income less the self-support amount). Jonah and Sian have 2 children, Koby aged 14 and Ryan aged 10. Jonah has another child support case with Winfried for child Bran, aged 5. The multi-case child costs for Koby and Ryan would be:

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

Costs of Ryan (10 years old)
= $20,000 × $0.27 (3+ children aged 0 - 12 years from the Costs of the 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 (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: Julie has children from 3 relationships. Julie and Charlton have 2 children, Jesse and Kevin. Julie and Josef have 1 child, Patricia. Josef also has an assessment with Hildegard for their children, Debi and Raul. Julie and Ruben have 2 children, Reginald and Jaron.

In calculating Julie's child support income for the assessment for Jesse and Kevin, the multi-case allowance is the sum of the multi-case costs of Patricia, Reginald and Jaron.

In calculating Julie's child support income for the assessment for Patricia, the multi-case allowance is the sum of the multi-case costs of Jesse, Kevin, Reginald and Jaron. Josef will also have a multi-case allowance, being the multi-case costs of Debi and Raul.

In calculating Julie's child support income for the assessment for Reginald and Jaron, the multi-case allowance is the sum of the multi-case costs of Jesse, Kevin and Patricia.

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. 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 (section 156).

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

Child support income for Sam

Multi-case allowance = multi-case costs of Moses + Adel
= $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 paying 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, multiplied by the costs that the parent does not meet directly through care (100% less their cost percentage) (section 55E). That is:
(100% − cost percentage) × multi-case child costs.

Example: If Edward has regular care of child Irene, and therefore a cost percentage of 24% for Irene, and Irene'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 1 household. Both the cap and the allowance are methods of recognising the parent's other obligations, so only 1 method is needed at any one time.

Only 1 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 multi-case 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

This formula is used to work out the annual rate of child support payable for a child when 1 or both of the parents have at least 1 other case, and there is no non-parent carer (section 37).

Step 1: Work out each parent's child support income (2.4.7) (section 41), by using the following formula:

  • parent's adjusted taxable income in that child support case
  • less the self-support amount
  • less the parent's relevant dependent child amount (if applicable)
  • less the parent's multi-case allowance for the child.

Where a parent has more than 1 child support case, their child support income needs to be calculated separately for each case, as the parent's adjusted taxable income and multi-case allowance may differ across their child support cases.

First, take the parent's adjusted taxable income applicable to that child support case and deduct the self-support amount.

Second, if applicable, work out a relevant dependent child (2.4.6) amount (section 46), and deduct the relevant dependent child amount from the amount above.

Third, if the parent has more than 1 child support case, work out the parent's multi-case allowance (section 47) and deduct the multi-case allowance from the amount above.

The final result is the parent's child support income for that case.

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 pay child support does not have more than 1 child support case.

Step 9 (if applicable): If a parent has more than 1 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 annual rate calculated at step 8, or the multi-case cap calculated at step 9.

Example: Formula 3 calculations

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

Step 1: Work out each parent's child support income Vincent Sigrid
Work out each parent's adjusted taxable income for this case $45,000 $40,000
Deduct the self-support amount − $18,252 − $18,252
Deduct a relevant dependent child amount, if applicable N/A N/A

Determine multi-case child costs for each of the children in each parent's other child support cases:

  • Relevant parent's income (adjusted taxable income − self-support amount − relevant dependent child amount)
  • Multiply by cost of the child based on child's age and parent's income (refer to Costs of the Children table)
  • Divide by number of the parent's child support children

Multi-case cost of each child

Costs of Geraldine (14 years old)
$26,748 × $0.32 (fraction of MTAWE = 0.5, children aged 13+ years, 3+ children) ÷ 3
= $2,853

Costs of Thomas (10 years old)
$26,748 × $0.27 (fraction of MTAWE = 0.5, children aged 0-12 years, 3+ children) ÷ 3
= $2,407

N/A

Deduct a multi-case allowance amount:

  • sum of the multi-case child costs for the children of the other case/s

− ($2,853 + $2,407)
= − $5,260

N/A
Each parent's child support income = $45,000 − $18,252 − $0 − $5,260
= $21,488
= $40,000 − $18,252 − $0 − $0
= $21,748
Step 2: Work out the combined child support income Vincent Sigrid
Each parent's child support income $21,488 $21,748
Combined child support income

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

Step 3: Work out each parent's income percentage Vincent Sigrid
Each parent's child support income
Divide by the combined child support income
Multiply the resulting amount by 100
Each parent's income percentage
$21,488
÷ $43,236
× 100
= 49.70%
$21,748
÷ $43,236
× 100
= 50.30%
Step 4: Work out each parent's percentage of care Vincent Sigrid
Each parent's care percentage
To work this out, see 2.2.1.
75 nights = 20.55%
Rounded to = 20%
290 nights = 79.45%
Rounded to = 80%
Step 5: Work out each parent's cost percentage Vincent Sigrid
Each parent's cost percentage
To work this out, see the Cost percentage table in 2.4.5.
= 24% = 76%
Step 6: Work out each parent's child support percentage Vincent Sigrid
Each parent's income percentage
Deduct each parent's cost percentage
Each parent's child support percentage
49.70%
− 24%
= 25.70%
50.30%
− 76%
= −25.70%

A parent who has a positive child support percentage will need to pay child support.

This means that Vincent is responsible for 49.70% of Honoria's costs because Vincent has 49.70% of the combined child support income. As Vincent meets only 24% of the costs through care, Vincent needs to transfer 25.70% of the costs to Sigrid through child support.

Step 7: Work out the costs of each child Honoria
Combined child support income $43,236
Using the relevant Costs of the Children table, calculate the total costs of the child
(for Honoria: 2008, fraction of MTAWE = 1, children aged 0-12 years, 1 child)
= $4,654 + ($0.15 for every $1 over $27,378)
= $4,654 + (($43,236 − $27,378) × $0.15)
= $4,654 + ($15,858 × $0.15)
= $4,654 + $2,379
= $7,033
Step 8: Work out the annual rate of child support payable by the parent with a positive child support percentage Vincent
Vincent's child support percentage
Multiply by the total cost of the children
Amount of child support for each child
25.70%
× $7,033
= $1,807
If the parent has more than 1 child support case, follow the next step.
Step 9 (if applicable): Work out the multi-case cap Vincent

Work out the multi-case child costs for the children in the child support case:

  • Paying parent's income (adjusted taxable income − self-support amount − relevant dependent child amount)
  • Multiply by cost of the child based on child's age and parent's income (refer to Costs of the Children table)
  • Divide by number of the parent's child support children

Multi-case cost for Honoria

Costs of Honoria (5 years old)
$26,748
× $0.27 (fraction of MTAWE = 0.5, children aged 0-12 years, 3 children)
÷ 3
= $2,407
Work out the multi-case cap for Honoria:
(100% − cost percentage) × multi-case child costs for Honoria
= (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) calculated at Step 9, the Step 8 amount is payable.
Vincent is liable to pay Sigrid child support for Honoria of $1,807 (annual rate).

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

This formula is used to work out the annual rate of child support payable for a child when 1 or both of the parents have at least 1 other case, and 1 or more non-parent carers has at least 35% care of a child (section 38).

Step 1: Work out each parent's child support income (2.4.7) (section 41), by using the following formula:

  • Parent's adjusted taxable income in that child support case,
  • less the self-support amount,
  • less the parent's relevant dependent child amount (if applicable),
  • less the parent's multi-case allowance for the child.

Where a parent has more than 1 child support case, their child support income needs to be calculated separately for each case, as the parent's adjusted taxable income and multi-case allowance may differ across their child support cases.

First, take the parent's adjusted taxable income applicable to that child support case and deduct the self-support amount.

Second, if applicable, work out a relevant dependent child (2.4.6) amount (section 46), and deduct the relevant dependent child amount from the amount above.

Third, if the parent has more than 1 child support case, work out the parent's multi-case allowance (section 47) and deduct the multi-case allowance from the amount above.

The final result is the parent's child support income for that case.

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 6, 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 pay child support does not have more than 1 child support case.

Step 9 (if applicable): If a parent has more than 1 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 annual rate calculated at step 8, or the multi-case cap calculated at step 9.

Example: Formula 4 calculations

Aliya and Edmund have 2 children, Kristina aged 14 and Harriette aged 10. Aliya has another child support case with Marcus for child Claudia, aged 7. Aliya also has another child Louisa, aged 4, living with them. There is no assessment for Louisa. Aliya has an adjusted taxable income of $45,000 and Edmund has an adjusted taxable income of $70,000.

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

Step 1: Work out each parent's child support income Aliya Edmund
Work out each parent's adjusted taxable income for this case $45,000 $70,000
Deduct the self-support amount − $18,252 −$18,252

Deduct a relevant dependent child amount, if applicable.

To work this out, see 2.4.4.20.

Costs of Louisa (4 years old)
− (($45,000 − $18,252) × $0.17)
= − ($26,748 × $0.17) (fraction of MTAWE = 0.5, children aged 0-12 years, 1 child)
= − $4,547
N/A

Determine multi-case child costs for each of the children in each parent's other child support cases:

  • Relevant parent's income (adjusted taxable income − self-support amount − relevant dependent child amount)
  • Multiply by cost of the child based on child's age and parent's income (refer to Costs of the Children table)
  • Divide by number of the parent's child support children

Multi-case cost of each child

Costs of Claudia (7 years old)

$22,201

× $0.27 (fraction of MTAWE = 0.5, children aged 0-12 years, 3+ children)

÷ 3

= $1,998

N/A
Deduct a multi-case allowance amount:
sum of the multi-case child costs for the children of the other case/s
− $1,998 N/A
Each parent's child support income = $45,000 − $18,252 − $4,547 − $1,998
= $20,203
= $70,000 − $18,252 − $0 − $0
= $51,748
Step 2: Work out the combined child support income Aliya Edmund
Each parent's child support income $20,203 $51,748
Combined child support income = $20,203 + $51,748
= $71,951
Step 3: Work out each parent's income percentage Aliya Edmund
Each parent's child support income
Divide by the combined child support income
Multiply the resulting amount by 100
Each parent's income percentage
$20,203
÷ $71,951
× 100
= 28.08%
$51,748
÷ $71,951
× 100
= 71.92%
Step 4: Work out each parent's percentage of care for each child Aliya Edmund
Each parent's care percentage
To work this out, see 2.2.1.
Aliya has 0% care of Kristina. Aliya has 0% care of Harriette. Edmund has 100% care of Kristina. Edmund has 0% care of Harriette.
Step 5: Work out each parent's cost percentage for each child Aliya Edmund
Each parent's cost percentage
To work this out, see the Cost percentage table in 2.4.5.
Aliya has a cost percentage of 0% for Kristina. Aliya has a cost percentage of 0% for Harriette. Edmund has a cost percentage of 100% for Kristina. Edmund has a cost percentage of 0% for Harriette.
Step 6: Work out each parent's child support percentage for each child Aliya Edmund
Each parent's income percentage 28.08% 71.92%
Deduct each parent's cost percentage − 0% for Kristina − 0% for Harriette − 100% for Kristina − 0% for Harriette
Each parent's child support percentage = 28.08% for both Kristina and Harriette = −28.08% for Kristina = 71.92% for Harriette

A parent who has a positive child support percentage will need to pay child support.

This means that Aliya is responsible for 28.08% of the costs of Kristina and Harriette, because Aliyah has 28.08% of the combined child support income. As Aliya does not meet any of the costs through care, they need to transfer 28.08% of the costs to the carers through child support.

Edmund is entitled to receive child support from Aliya for Kristina and is required to pay child support for Harriette.

Step 7: Work out the costs of each child Kristina (14 years old) Harriette (10 years old)
Combined child support income of the parents $71,951 $71,951
Using the relevant Costs of the Children table, calculate the total costs of the child

(for Kristina: 2008, fraction of MTAWE = 1.5, children aged 13+ years, 2 children)
= ($15,606 + ($0.25 for every $1 over $54,756)) ÷ 2
= ($15,606 + (($71,951 − $54,756) × $0.25)) ÷ 2
= ($15,606 + ($17,195 × $0.25)) ÷ 2
= ($15,606 + $4,299) ÷ 2
= $19,905 ÷ 2
= $9,953

(for Harriette: 2008, fraction of MTAWE = 1.5, children aged 0-12 years, 2 children)
= ($12,868 + ($0.20 for every $1 over $54,756)) ÷ 2
= ($12,868 + (($71,951 − $54,756) × $0.20)) ÷ 2
= ($12,868 + ($17,195 × $0.20)) ÷ 2
= ($12,868 + $3,439) ÷ 2
= $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

Kristina
(Aliya is liable to pay Edmund)

Harriette
(Both Aliya and Edmund are liable to pay Ali, as they both have positive child support percentages for Harriette)

Aliya Edmund
Paying parent's child support percentage
Multiply by the cost of the children
Amount of child support for each child
28.08%
× $9,953
= $2,795
28.08%
× $8,154
= $2,290
71.92%
× $8,154
= $5,864
If the parent has more than 1 child support case, follow the next step.
Step 9 (if applicable): Work out the multi-case cap

Kristina
(This step is applicable only to Aliya)

Harriette
(This step is applicable only to Aliya)

Work out the multi-case child costs for the children in the child support case:

See instructions above in Step 1.

 

Multi-case costs of Kristina (14 years)
(2008, fraction of MTAWE = 0.5, children aged 13+ years, 3 children)

= ($45,000 − $18,252 − $4,547) × &$0.32 ÷ 3
= $22,201 × $0.32 ÷ 3
= $2,368

 

Multi-case costs of Harriette (10 years)
(2008, fraction of MTAWE = 0.5, children aged 0-12 years, 3 children)

= ($45,000 − $18,252 − $4,547) × $0.27 ÷ 3
= $22,201 × $0.27 ÷ 3
= $1,998

 

Work out the multi-case cap for each child:

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

= (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) calculated at Step 9, the multi-case cap is payable by Aliya.

= (100% − 0%) × $1,998
= 100% × $1,998
= $1,998

As the amount calculated at step 8 ($2,290) is more than the multi-case cap ($1,998) calculated at Step 9, the multi-case cap is payable by Aliya.

Child support payable

Aliya is liable to pay Edmund child support for Kristina of $2,368 (multi-case cap).

Aliya is liable to pay Ali child support for Harriette of $1,998 (multi-case cap).

Edmund is to pay Ali child support for Harriette of $5,864 (annual rate).

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

When child support is payable by or to more than 1 person under Formula 4

If … then …
Example
both parents have a positive child support percentage at step 6 of the formula calculations both parents pay child support to the non-parent carer/s (section 38(5)).

The first parent, Ted, has a child support percentage of 83.47%. The second parent, Rita, 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 Valerie, who has full-time care of the child.

Ted will pay $1,000 × 83.47% = $835.

Rita will pay $1,000 × 16.53% = $165.

1 parent has a positive child support percentage at step 6, and the other parent has:

a nil or negative child support percentage, and

less than shared care

only the first parent pays child support to the non-parent carer/s (section 38(5)).

The first parent, Arnold, has a child support percentage of 83.47%. The second parent, Olivia, 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.

Arnold is required to pay child support to Robert, who has primary care of the child.

Arnold will pay $1,000 × 83.47% = $835.

1 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

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.

The first parent, Marcela, has a child support percentage of 83.47%. The second parent Frederique, 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, June, has 49% care of the child (shared care) which is a cost percentage of 50%.

The costs of the child are $1,000.

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

Marcela is required to pay child support to Frederique, using Frederique's cost percentage divided by the combined cost percentages of Frederique and June.

Marcela will pay 835 × 29% ÷ (29% + 50%) = $307 to Frederique.

Marcela is required to pay child support to June using June's cost percentage divided by the combined cost percentages of June and Frederique.

Marcela will pay 835 × 50% ÷ (29% + 50%) = $528 to June.

A non-parent carer is not entitled to be paid child support unless they have at least 35% care of the child (section 7B) and they have applied under section 25A (section 40B). If more than 1 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 1 person.

Different rules apply if the minimum annual rate of child support is payable to more than 1 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: 1 July 2019