Basic formula

This formula is for parents with only 1 child support assessment.

Read about parents with 2 or more assessments.

This page is for general information. To calculate an estimate of your child support payments you can use our child support estimator.

Basic 8 step formula

Step What we do This step is about
1
Work out each parent’s child support income

We calculate each parent’s child support income. This is a parent’s adjusted taxable income minus a self-support amount and any relevant dependant allowance. For more information about relevant dependant allowances, go to child support assessments and second families.

A parent may be able to estimate their income. Read more about income used in calculating a child support assessment.

Income
2
Work out the parents’ combined income
We add both parents' incomes to work out a combined child support income. Income
3
Work out each parent’s income percentage
We work out each parent’s income percentage by dividing each income by the combined total. Income
4
Work out each parent’s percentage of care
We calculate each parent's percentage of care. Care
5
Work out each parent’s cost percentage
We work out each parent's cost percentage using the Care and Cost table. Care
6
Work out each parent’s child support percentage
We subtract the cost percentage from the income percentage for each parent. We call this the child support percentage. The result will determine if a parent pays or gets child support.

If it’s a negative percentage, we assess that parent as the parent to get child support. This is because their share of costs for the child is more than the amount of care they provide.

If it’s a positive percentage, we assess that parent as the parent to pay child support. This is because they’re not meeting their share of the costs for the child directly through care.

If you have different care arrangements for various children, you might have different child support percentages for each child.

We go on to steps 7 and 8 using only the positive child support percentage.

Child support percentage

7
Work out the costs of children

We work out the costs for each child based on the parents' combined total income. We do this by using the Costs of Children table.

Costs of children
8
Work out the child support amount
We work out the total amount of child support payable. We do this by multiplying the positive child support percentage by the costs of the child. If we assess both parents are to pay each other, we offset these amounts before arriving at the final figure. This final figure is the amount the paying parent needs to pay the other parent. Child support to pay

Care and cost table

Your care percentage is the amount of time you spend with the child. This helps us to work out your cost percentage.

Your cost percentage is your share of the child’s costs that you meet directly through care.

Care percentage Equal to number of nights a year Equal to number of nights a fortnight Care level Cost percentage
0-13% 0-51 1 Less than regular care 0%
14-34% 52-127 2-4 Regular care 24%
35-47% 128-175 5-6 Shared care 25% plus 2% for every percentage point over 35% of care
48-52% 176-189 7 Shared care 50%
53-65% 190-237 8-9 Shared care 51% plus 2% for every percentage point over 53% of care
66-86% 238-313 10-12 Primary care 76%
87-100% 314-365 13-14 More than primary care 100%

Read about how your percentage of care affects your child support.

Costs of children

The Costs of Children tables recognise that raising children costs different amounts for different people. Because of this we work out your children’s costs based on all of the following. The:

About the tables

Steps 1 and 2 of the basic 8 step formula explain what combined child support income is.

Under the formula, we deduct an amount for each parent to support themselves. We calculate the costs of raising children according to the remaining combined child support income of both parents. We divide the costs between the parents according to their share of the combined income.

The Costs of Children table represents net costs after Family Tax Benefit. All the figures in these tables are for child support periods starting in 2019.

Read about Costs of Children for past years in the Child Support Guide on the Department of Social Services website.

Children aged 12 and under

Parents combined child support income Cost of 1 child Cost of 2 children Cost of 3 or more children
$0 to $38,363 17c for each $1 24c for each $1 27c for each $1
$38,364 to $76,726 $6,522 plus 15c for each $1 over $38,363 $9,207 plus 23c for each $1 over $38,363 $10,358 plus 26c for each $1 over $38,363
$76,727 to $115,089 $12,276 plus 12c for each $1 over $76,726 $18,030 plus 20c for each $1 over $76,726 $20,332 plus 25c for each $1 over $76,726
$115,090 to $153,452 $16,880 plus 10c for each $1 over $115,089 $25,703 plus 18c for each $1 over $115,089 $29,923 plus 24c for each $1 over $115,089
$153,453 to $191,815 $20,716 plus 7c for each $1 over $153,452 $32,608 plus 10c for each $1 over $153,452 $39,130 plus 18c for each $1 over $153,452

Income over $191,815

Costs don’t go up past this cap

$23,401 $36,444 $46,035

Read more about parents combined child support income.

Children aged 13 or older

Combined child support income for 1 year Cost of 1 child Cost of 2 children Cost of 3 or more children
$0 to $38,363 23c for each $1 29c for each $1 32c for each $1
$38,364 to $76,726 $8,823 plus 22c for each $1 over $38,363 $11,125 plus 28c for each $1 over $38,363 $12,276 plus 31c for each $1 over $38,363
$76,727 to $115,089 $17,263 plus 12c for each $1 over $76,726 $21,867 plus 25c for each $1 over $76,726 $24,169 plus 30c for each $1 over $76,726
$115,090 to $153,452 $21,867 plus 10c for each $1 over $115,089 $31,458 plus 20c for each $1 over $115,089 $35,678 plus 29c for each $1 over $115,089
$153,453 to $191,815 $25,703 plus 9c for each $1 over $153,452 $39,131 plus 13c for each $1 over $153,452 $46,803 plus 20c for each $1 over $153,452

Income over $191,815

Costs don’t go up past this cap

$29,156 $44,118 $54,476

Read more about parents combined child support income.

Children of mixed ages

Combined Child Support income for 1 year Cost of 2 children Cost of 3 or more children
$0 to $38,363 26.5c for each $1 29.5c for each $1
$38,364 to $76,726 $10,166 plus 25.5c for each $1 over $38,363 $11,317 plus 28.5c for each $1 over $38,363
$76,727 to $115,089 $19,949 plus 22.5c for each $1 over $76,726 $22,250 plus 27.5c for each $1 over $76,726
$115,090 to $153,452 $28,581 plus 19c for each $1 over $115,089 $32,800 plus 26.5c for each $1 over $115,089
$153,453 to $191,815 $35,870 plus 11.5c for each $1 over $153,452 $42,966 plus 19c for each $1 over $153,452

Income over $191,815

Costs don’t go up past this cap

$40,282 $50,255

Read more about parents combined child support income.

Page last updated: 31 August 2020