Worked examples · 2026 assessment year
Australian Child Support Formula 1-6 Calculator Examples
Six fictional cases, one for each child support formula, worked through by the AusChildSupport calculator for the 2026 assessment year.
Every example is fictional and calculated by AusChildSupport’s own calculator. They are not Services Australia assessments, legal review or independent validation, and they do not cover every case. Read how the calculator is built and where its limits are.
Six worked examples
Each example gives the case, the result and the calculator’s full breakdown. For how the formulas work, read how child support is calculated.
Formula 1
Basic formula
When it applies: Only the two parents care for the children, and neither parent has a child in another child support case.
The case
- Parent A income
- $90,000
- Parent B income
- $50,000
- Children
- One aged 0 to 12
- Other cases or dependants
- None
- Care each fortnight
- Parent A 4 nights
- Parent B 10 nights
The result
- Parent A pays Parent B$6,520 per year
See the full breakdown
The breakdown is shown from Parent A’s side, so Parent A appears as “You”.
Result breakdown
Formula 1: The basic formula
This takes each parent's adjusted taxable income and sets aside a self-support amount, plus any allowance for other children they support, leaving the child support income the formula works with.
| You | Other parent | |
|---|---|---|
| Adjusted taxable income | $90,000 | $50,000 |
| Self-support amount | −$31,046 | −$31,046 |
| Child support income | $58,954 | $18,954 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20
This adds both parents' child support incomes into one combined figure, which is used to read the children's cost from the table and to measure each parent's share of the income.
| You | Other parent | |
|---|---|---|
| Child support income | $58,954 | $18,954 |
| Combined child support income | $77,908 | |
Sources Combined child support income (opens in a new tab) 1.1.C.190
This divides each parent's child support income by the combined figure, giving each parent's percentage share of the combined income, which is the share of the children's costs the formula expects that parent to meet.
| You | Other parent | |
|---|---|---|
| Child support income ÷ $77,908 | $58,954 | $18,954 |
| Income percentage | 75.67% | 24.33% |
Sources Income percentage (opens in a new tab) 1.1.I.30
This turns the care each parent provides into a percentage of the time, worked out separately for every child. It is the measure of care the next step converts into a share of costs.
| You | Other parent | |
|---|---|---|
| Nights per fortnight | 4 | 10 |
| Percentage of care | 28% | 72% |
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts each parent's percentage of care into a cost percentage using a set table of care bands, not a straight proportion. The cost percentage is the share of each child's costs that parent is treated as meeting through care.
| You | Other parent | |
|---|---|---|
| Cost percentage | 24%from 28% care | 76%from 72% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% | 0% |
| 14% to 34% (applies here) | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% (applies here) | 76% |
| 87% to 100% | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This takes each parent's cost percentage away from their income percentage for each child. A positive result shows that parent's care falls short of the share of costs their income points to, a negative result shows it goes beyond that share, and the later steps work out what that means in dollars.
| You | Other parent | |
|---|---|---|
| Income percentage | 75.67% | 24.33% |
| Cost percentage | −24% | −76% |
| Child support percentage | 51.67% | −51.67% |
The other parent's negative percentage means they don't pay child support for Child 1.
Sources Child support percentage (opens in a new tab) 1.1.C.140
This reads the yearly cost of the children from the Costs of the Children Table, using the parents' combined child support income and the number and age group of the children. It is a cost base that the percentages are applied to, not an amount anyone pays.
| Amount | |
|---|---|
| Costs of the child | $12,618 |
This is the average amount spent raising your child at your combined income, not the amount you pay.
Sources Costs of the child (opens in a new tab) 1.1.C.210
This multiplies each child's cost by each paying parent's child support percentage to give a yearly amount for each child, and adds those amounts up.
| Your annual rate | |
|---|---|
| Step 6 × Step 7 | |
| Child 1 | $6,52051.67% × $12,618 |
Sources Annual rate (opens in a new tab) 1.1.A.70
Formula source: DSS Child Support Guide 2.2.2
Formula 2
Single case with a non-parent carer
When it applies: A non-parent carer, such as a grandparent, has at least 35% care of a child, and neither parent has a child in another child support case.
The case
- Parent A income
- $90,000
- Parent B income
- $60,000
- Children
- One aged 0 to 12
- Care each fortnight
- Parent A 3 nights
- Parent B 2 nights
- Non-parent carer 9 nights
The result
- Parent A pays the non-parent carer$6,079 per year
- Parent B pays the non-parent carer$1,262 per year
See the full breakdown
The breakdown is shown from Parent A’s side, so Parent A appears as “You”.
Result breakdown
Formula 2: Single case with a non-parent carer
Formula 2 applies because a non-parent carer has qualifying care and neither parent has children in another child support assessment.
This takes each parent's adjusted taxable income and sets aside a self-support amount, plus any allowance for other children they support, leaving the child support income the formula works with.
| You | Other parent | |
|---|---|---|
| Adjusted taxable income | $90,000 | $60,000 |
| Self-support amount | −$31,046 | −$31,046 |
| Child support income | $58,954 | $28,954 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20
This adds both parents' child support incomes into one combined figure, which is used to read the children's cost from the table and to measure each parent's share of the income.
| You | Other parent | |
|---|---|---|
| Child support income | $58,954 | $28,954 |
| Combined child support income | $87,908 | |
Sources Combined child support income (opens in a new tab) 1.1.C.190
This divides each parent's child support income by the combined figure, giving each parent's percentage share of the combined income, which is the share of the children's costs the formula expects that parent to meet.
| You | Other parent | |
|---|---|---|
| Child support income ÷ $87,908 | $58,954 | $28,954 |
| Income percentage | 67.06% | 32.94% |
Sources Income percentage (opens in a new tab) 1.1.I.30
This turns the care each parent and the non-parent carer provides into a percentage of the time, worked out for every child. The parents' percentages are shown here and feed the next step; the carer's is carried to the final step, where it can be used to divide a rate that is shared.
| You | Other parent | |
|---|---|---|
| Nights per fortnight | 3 | 2 |
| Percentage of care | 21% | 14% |
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts each parent's percentage of care into a cost percentage using a set table of care bands, not a straight proportion: the share of each child's costs that parent is treated as meeting through care. The non-parent carer's cost percentage is worked out the same way and can be used at the final step when a rate is shared.
| You | Other parent | |
|---|---|---|
| Cost percentage | 24%from 21% care | 24%from 14% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% | 0% |
| 14% to 34% (applies here) | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% | 76% |
| 87% to 100% | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This takes each parent's cost percentage away from their income percentage for each child. A positive result shows that parent's care falls short of the share of costs their income points to, a negative result shows it goes beyond that share, and the later steps work out what that means in dollars.
| You | Other parent | |
|---|---|---|
| Income percentage | 67.06% | 32.94% |
| Cost percentage | −24% | −24% |
| Child support percentage | 43.06% | 8.94% |
Sources Child support percentage (opens in a new tab) 1.1.C.140
This reads the yearly cost of the children from the Costs of the Children Table, using the parents' combined child support income and the number and age group of the children. It is a cost base that the percentages are applied to, not an amount anyone pays.
| Amount | |
|---|---|
| Costs of the child | $14,118 |
This is the average amount spent raising your child at your combined income, not the amount you pay.
Sources Costs of the child (opens in a new tab) 1.1.C.210
This multiplies each child's cost by each paying parent's child support percentage to give a yearly amount for each child, which goes to whoever is entitled to receive it for that child.
| You | Other parent | |
|---|---|---|
| Step 6 × Step 7 | ||
| Child 1 (non-parent carer) | $6,07943.06% × $14,118 | $1,2628.94% × $14,118 |
Payments
- You pay the non-parent carer$6,079
- Other parent pays the non-parent carer$1,262
Sources Annual rate (opens in a new tab) 1.1.A.70
Formula source: DSS Child Support Guide 2.2.3
Formula 3
Multiple child support cases
When it applies: At least one parent also has a child in another child support case.
The case
- Parent A income
- $105,000
- Parent A also has
- One relevant dependent child aged 0 to 12
- Parent B income
- $65,000
- Parent B also has
- One child aged 13 plus in another child support case
- Children in this case
- Two: one aged 0 to 12 and one aged 13 plus
- Care each fortnight
- Parent A 4 nights
- Parent B 10 nights
The result
- Parent A pays Parent B$10,346 per year
See the full breakdown
The breakdown is shown from Parent A’s side, so Parent A appears as “You”.
Result breakdown
Formula 3: Multiple child support cases
Formula 3 applies because the other parent has children in another child support assessment, so a multi-case allowance, a multi-case cost for each child and a multi-case cap are added to the basic formula.
This takes each parent's adjusted taxable income and sets aside a self-support amount, plus any allowance for other children they support, leaving the child support income the formula works with.
| You | Other parent | |
|---|---|---|
| Adjusted taxable income | $105,000 | $65,000 |
| Self-support amount | −$31,046 | −$31,046 |
| Relevant dependent child amount | −$12,025 | — |
| Multi-case allowance | — | −$3,622 |
| Child support income | $61,929 | $30,332 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20Relevant dependent child amount (opens in a new tab) 3.1.2Multi-case allowance (opens in a new tab) 1.1.M.30
This adds both parents' child support incomes into one combined figure, which is used to read the children's cost from the table and to measure each parent's share of the income.
| You | Other parent | |
|---|---|---|
| Child support income | $61,929 | $30,332 |
| Combined child support income | $92,261 | |
Sources Combined child support income (opens in a new tab) 1.1.C.190
This divides each parent's child support income by the combined figure, giving each parent's percentage share of the combined income, which is the share of the children's costs the formula expects that parent to meet.
| You | Other parent | |
|---|---|---|
| Child support income ÷ $92,261 | $61,929 | $30,332 |
| Income percentage | 67.12% | 32.88% |
Sources Income percentage (opens in a new tab) 1.1.I.30
This turns the care each parent provides into a percentage of the time, worked out separately for every child. It is the measure of care the next step converts into a share of costs.
| You | Other parent | |
|---|---|---|
| Nights per fortnight | 4 | 10 |
| Percentage of care | 28% | 72% |
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts each parent's percentage of care into a cost percentage using a set table of care bands, not a straight proportion. The cost percentage is the share of each child's costs that parent is treated as meeting through care.
| You | Other parent | |
|---|---|---|
| Cost percentage | 24%from 28% care | 76%from 72% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% | 0% |
| 14% to 34% (applies here) | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% (applies here) | 76% |
| 87% to 100% | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This takes each parent's cost percentage away from their income percentage for each child. A positive result shows that parent's care falls short of the share of costs their income points to, a negative result shows it goes beyond that share, and the later steps work out what that means in dollars.
| You | Other parent | |
|---|---|---|
| Income percentage | 67.12% | 32.88% |
| Cost percentage | −24% | −76% |
| Child support percentage | 43.12% | −43.12% |
The other parent's negative percentage means they don't pay child support for Children 1 and 2.
Sources Child support percentage (opens in a new tab) 1.1.C.140
This works out a cost for each child on its own, because a parent has another child support case: the table amount at the parents' combined child support income as if every child in the case were that child's age, divided by the number of children in the case. Children of different ages can therefore get different costs.
| Amount | |
|---|---|
| Cost of 2 children, all under 13 | $21,686 |
| Per child | $10,843 |
| Amount | |
|---|---|
| Cost of 2 children, all 13 or over | $26,299 |
| Per child | $13,150 |
This is the average amount spent raising your children at your combined income, not the amount you pay.
Sources Costs of the child (opens in a new tab) 1.1.C.210
This multiplies each child's cost by the paying parent's child support percentage and adds the children's amounts up. Any multi-case cap that applies was also checked and was not lower for any child, so this is the annual rate.
| Your annual rate | |
|---|---|
| F1 Step 6 × Step 1A | |
| Child 1 | $4,67643.12% × $10,843 |
| Child 2 | $5,67043.12% × $13,150 |
| Total | $10,346 |
Sources Annual rate (opens in a new tab) 1.1.A.70
Formula source: DSS Child Support Guide 2.2.4
Formula 4
Multiple cases with a non-parent carer
When it applies: A non-parent carer is involved, and at least one parent also has a child in another child support case.
The case
- Parent A income
- $90,000
- Parent B income
- $60,000
- Parent B also has
- One child aged 0 to 12 in another child support case
- Children in this case
- One aged 0 to 12
- Care each fortnight
- Parent A 3 nights
- Parent B 2 nights
- Non-parent carer 9 nights
The result
- Parent A pays the non-parent carer$6,230 per year
- Parent B pays the non-parent carer$840 per year
See the full breakdown
The breakdown is shown from Parent A’s side, so Parent A appears as “You”.
Result breakdown
Formula 4: Multiple child support cases with a non-parent carer
Formula 4 applies because a non-parent carer has qualifying care and at least one parent has children in another child support assessment.
This takes each parent's adjusted taxable income and sets aside a self-support amount, plus any allowance for other children they support, leaving the child support income the formula works with.
| You | Other parent | |
|---|---|---|
| Adjusted taxable income | $90,000 | $60,000 |
| Self-support amount | −$31,046 | −$31,046 |
| Multi-case allowance | — | −$3,475 |
| Child support income | $58,954 | $25,479 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20Multi-case allowance (opens in a new tab) 1.1.M.30
This adds both parents' child support incomes into one combined figure, which is used to read the children's cost from the table and to measure each parent's share of the income.
| You | Other parent | |
|---|---|---|
| Child support income | $58,954 | $25,479 |
| Combined child support income | $84,433 | |
Sources Combined child support income (opens in a new tab) 1.1.C.190
This divides each parent's child support income by the combined figure, giving each parent's percentage share of the combined income, which is the share of the children's costs the formula expects that parent to meet.
| You | Other parent | |
|---|---|---|
| Child support income ÷ $84,433 | $58,954 | $25,479 |
| Income percentage | 69.82% | 30.18% |
Sources Income percentage (opens in a new tab) 1.1.I.30
This turns the care each parent and the non-parent carer provides into a percentage of the time, worked out for every child. The parents' percentages are shown here and feed the next step; the carer's is carried to the final step, where it can be used to divide a rate that is shared.
| You | Other parent | |
|---|---|---|
| Nights per fortnight | 3 | 2 |
| Percentage of care | 21% | 14% |
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts each parent's percentage of care into a cost percentage using a set table of care bands, not a straight proportion: the share of each child's costs that parent is treated as meeting through care. The non-parent carer's cost percentage is worked out the same way and can be used at the final step when a rate is shared.
| You | Other parent | |
|---|---|---|
| Cost percentage | 24%from 21% care | 24%from 14% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% | 0% |
| 14% to 34% (applies here) | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% | 76% |
| 87% to 100% | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This takes each parent's cost percentage away from their income percentage for each child. A positive result shows that parent's care falls short of the share of costs their income points to, a negative result shows it goes beyond that share, and the later steps work out what that means in dollars.
| You | Other parent | |
|---|---|---|
| Income percentage | 69.82% | 30.18% |
| Cost percentage | −24% | −24% |
| Child support percentage | 45.82% | 6.18% |
Sources Child support percentage (opens in a new tab) 1.1.C.140
This works out a cost for each child on its own, because a parent has another child support case: the table amount at the parents' combined child support income as if every child in the case were that child's age, divided by the number of children in the case. Children of different ages can therefore get different costs.
| Amount | |
|---|---|
| Cost of 1 child, under 13 | $13,597 |
This is the average amount spent raising your child at your combined income, not the amount you pay.
Sources Costs of the child (opens in a new tab) 1.1.C.210
This multiplies each child's cost by each paying parent's child support percentage, and each amount goes to whoever is entitled to receive it for that child. Any multi-case cap that applies was also checked and was not lower for any child, so this is the annual rate.
| You | Other parent | |
|---|---|---|
| F1 Step 6 × Step 2A | ||
| Child 1 (non-parent carer) | $6,23045.82% × $13,597 | $8406.18% × $13,597 |
Payments
- You pay the non-parent carer$6,230
- Other parent pays the non-parent carer$840
Sources Annual rate (opens in a new tab) 1.1.A.70
Formula source: DSS Child Support Guide 2.2.5
Formula 5
One-parent income assessment
When it applies: A non-parent carer applies and only one parent’s income can be assessed, usually because the other parent lives overseas in a non-reciprocating jurisdiction.
The case
- Parent A income
- $80,000
- Parent B
- Lives overseas in a non-reciprocating jurisdiction; income not assessed
- Children
- One aged 0 to 12
- Care each fortnight
- Parent A 4 nights
- Non-parent carer 10 nights
The result
- Parent A pays the non-parent carer$5,881 per year
See the full breakdown
The breakdown is shown from Parent A’s side, so Parent A appears as “You”.
Result breakdown
Formula 5: Assessments using the income of only one parent
Formula 5 applies because this is a one-parent assessment, so only one parent's income is used, and a non-parent carer has qualifying care.
This works out the child support income of the one parent whose income is used in this estimate: their adjusted taxable income less a self-support amount and any allowance for other children they support.
| Amount | |
|---|---|
| Adjusted taxable income | $80,000 |
| Self-support amount | −$31,046 |
| Child support income | $48,954 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20
This records, for each child, the share of the time the parent in this estimate cares for that child, as a percentage. It is the measure the next step turns into a share of the child's costs; the non-parent carer's care is used later only when two carers share the rate.
| Amount | |
|---|---|
| Nights per fortnight | 4 |
| Percentage of care | 28% |
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts the parent's percentage of care for each child into a cost percentage using a set table of care bands, not a straight proportion: the share of that child's costs the parent is treated as meeting through care, which the rate step takes off the child's cost.
| Amount | |
|---|---|
| Cost percentage | 24%from 28% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% | 0% |
| 14% to 34% (applies here) | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% | 76% |
| 87% to 100% | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This doubles the parent's child support income to stand in for two parents' incomes, then reads the children's yearly cost from the Costs of the Children Table for that figure and the number and age group of the children. The rate step halves the result again so the parent carries one parent's share.
| Amount | |
|---|---|
| Child support income × 2 | $97,908 |
| Cost of the child | $15,475 |
Sources Costs of the child (opens in a new tab) 1.1.C.210
For each child this takes the parent's cost percentage of the child's cost away from that cost and halves what is left. The result is the yearly amount paid to the non-parent carer, or shared between two carers in proportion to their cost percentages.
| Amount | |
|---|---|
| Cost percentage × cost | $3,71424% × $15,475 |
| Cost less that amount | $11,761$15,475 − $3,714 |
| Half | $5,881 |
Sources Annual rate (opens in a new tab) 1.1.A.70
Formula source: DSS Child Support Guide 2.2.6
Formula 6
One-parent income assessment with a deceased parent
When it applies: A non-parent carer applies and one parent has died.
The case
- Parent A income
- $80,000
- Parent B
- Deceased
- Children
- One aged 0 to 12
- Care each fortnight
- Parent A 4 nights
- Non-parent carer 10 nights
The result
- Parent A pays the non-parent carer$6,289 per year
See the full breakdown
The breakdown is shown from Parent A’s side, so Parent A appears as “You”.
Result breakdown
Formula 6: Assessments using the income of only one parent
Formula 6 applies because one of the child's parents has died, so only the surviving parent's income is used.
This works out the child support income of the one parent whose income is used in this estimate: their adjusted taxable income less a self-support amount and any allowance for other children they support.
| Amount | |
|---|---|
| Adjusted taxable income | $80,000 |
| Self-support amount | −$31,046 |
| Child support income | $48,954 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20
This records, for each child, the share of the time the parent in this estimate cares for that child, as a percentage. It is the measure the next step turns into a share of the child's costs; the non-parent carer's care is used later only when two carers share the rate.
| Amount | |
|---|---|
| Nights per fortnight | 4 |
| Percentage of care | 28% |
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts the parent's percentage of care for each child into a cost percentage using a set table of care bands, not a straight proportion: the share of that child's costs the parent is treated as meeting through care, which the rate step takes off the child's cost.
| Amount | |
|---|---|
| Cost percentage | 24%from 28% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% | 0% |
| 14% to 34% (applies here) | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% | 76% |
| 87% to 100% | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This reads the children's yearly cost from the Costs of the Children Table using the surviving parent's child support income and the number and age group of the children. Nothing is doubled or halved in this formula.
| Amount | |
|---|---|
| Cost of the child | $8,275 |
Sources Costs of the child (opens in a new tab) 1.1.C.210
For each child this takes the parent's cost percentage of the child's cost away from that cost, with no halving, because the parent's income was not doubled in working out that cost. What is left is the yearly amount paid to the non-parent carer, or shared between two carers in proportion to their cost percentages.
| Amount | |
|---|---|
| Cost percentage × cost | $1,98624% × $8,275 |
| Cost less that amount | $6,289$8,275 − $1,986 |
Sources Annual rate (opens in a new tab) 1.1.A.70
Formula source: DSS Child Support Guide 2.2.7
Three DSS guide examples, run in the guide’s own year
The DSS Child Support Guide publishes worked examples for Formula 1, Formula 3 and Formula 4. Each one below is run through the calculator with the same assessment-year values the guide used, and shown beside the guide’s figure. A match on these examples does not guarantee a match with a Services Australia assessment.
Formula 1
2025 rates
DSS Formula 1 example
Mark and Lisette have three children aged 0 to 12, who spend 290 nights a year with Mark and 75 with Lisette.
| Payment | DSS guide | Calculator | Difference |
|---|---|---|---|
| Lisette pays Mark | $4,863 | $4,863 | None |
The calculator returns the same figure the guide publishes.
See the full breakdown
The case
- Mark’s income
- $50,000
- Lisette’s income
- $60,000
- Children
- Three aged 0 to 12
- Care
- Mark 290 nights a year, Lisette 75
The breakdown is shown from Mark’s side, so Mark appears as “You”.
Result breakdown
Formula 1: The basic formula
This takes each parent's adjusted taxable income and sets aside a self-support amount, plus any allowance for other children they support, leaving the child support income the formula works with.
| You | Other parent | |
|---|---|---|
| Adjusted taxable income | $50,000 | $60,000 |
| Self-support amount | −$29,841 | −$29,841 |
| Child support income | $20,159 | $30,159 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20
This adds both parents' child support incomes into one combined figure, which is used to read the children's cost from the table and to measure each parent's share of the income.
| You | Other parent | |
|---|---|---|
| Child support income | $20,159 | $30,159 |
| Combined child support income | $50,318 | |
Sources Combined child support income (opens in a new tab) 1.1.C.190
This divides each parent's child support income by the combined figure, giving each parent's percentage share of the combined income, which is the share of the children's costs the formula expects that parent to meet.
| You | Other parent | |
|---|---|---|
| Child support income ÷ $50,318 | $20,159 | $30,159 |
| Income percentage | 40.06% | 59.94% |
Sources Income percentage (opens in a new tab) 1.1.I.30
This turns the care each parent provides into a percentage of the time, worked out separately for every child. It is the measure of care the next step converts into a share of costs.
| You | Other parent | |
|---|---|---|
| Nights per year | 290 | 75 |
| Percentage of care | 80% | 20% |
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts each parent's percentage of care into a cost percentage using a set table of care bands, not a straight proportion. The cost percentage is the share of each child's costs that parent is treated as meeting through care.
| You | Other parent | |
|---|---|---|
| Cost percentage | 76%from 80% care | 24%from 20% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% | 0% |
| 14% to 34% (applies here) | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% (applies here) | 76% |
| 87% to 100% | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This takes each parent's cost percentage away from their income percentage for each child. A positive result shows that parent's care falls short of the share of costs their income points to, a negative result shows it goes beyond that share, and the later steps work out what that means in dollars.
| You | Other parent | |
|---|---|---|
| Income percentage | 40.06% | 59.94% |
| Cost percentage | −76% | −24% |
| Child support percentage | −35.94% | 35.94% |
Your negative percentage means you don't pay child support for Children 1, 2 and 3.
Sources Child support percentage (opens in a new tab) 1.1.C.140
This reads the yearly cost of the children from the Costs of the Children Table, using the parents' combined child support income and the number and age group of the children. It is a cost base that the percentages are applied to, not an amount anyone pays.
| Amount | |
|---|---|
| Costs of the children | $13,531 |
| Per child | $4,510 |
This is the average amount spent raising your children at your combined income, not the amount you pay.
Sources Costs of the child (opens in a new tab) 1.1.C.210
This multiplies each child's cost by each paying parent's child support percentage to give a yearly amount for each child, and adds those amounts up.
| Other parent's annual rate | |
|---|---|
| Step 6 × Step 7 | |
| Child 1 | $1,62135.94% × $4,510 |
| Child 2 | $1,62135.94% × $4,510 |
| Child 3 | $1,62135.94% × $4,510 |
| Total | $4,863 |
Sources Annual rate (opens in a new tab) 1.1.A.70
Guide example: DSS Child Support Guide 2.2.2, “Example — Using 2025 rates”
Formula 3
2024 rates
DSS Formula 3 example
Vincent and Faith have two children, one aged 13 plus and one aged 0 to 12, who spend 75 nights a year with Vincent. Vincent also has a child aged 0 to 12 in a second child support case.
| Payment | DSS guide | Calculator | Difference |
|---|---|---|---|
| Vincent pays Faith | $3,219 | $3,219 | None |
The calculator returns the same figure the guide publishes.
See the full breakdown
The case
- Vincent’s income
- $50,000
- Faith’s income
- $35,000
- Children in this case
- Two: one aged 13 plus and one aged 0 to 12
- Care
- Vincent 75 nights a year, Faith 290
- Vincent also has
- One child aged 0 to 12 in another child support case
The breakdown is shown from Vincent’s side, so Vincent appears as “You”.
Result breakdown
Formula 3: Multiple child support cases
Formula 3 applies because you have children in another child support assessment, so a multi-case allowance, a multi-case cost for each child and a multi-case cap are added to the basic formula.
This takes each parent's adjusted taxable income and sets aside a self-support amount, plus any allowance for other children they support, leaving the child support income the formula works with.
| You | Other parent | |
|---|---|---|
| Adjusted taxable income | $50,000 | $35,000 |
| Self-support amount | −$28,463 | −$28,463 |
| Multi-case allowance | −$1,938 | — |
| Child support income | $19,599 | $6,537 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20Multi-case allowance (opens in a new tab) 1.1.M.30
This adds both parents' child support incomes into one combined figure, which is used to read the children's cost from the table and to measure each parent's share of the income.
| You | Other parent | |
|---|---|---|
| Child support income | $19,599 | $6,537 |
| Combined child support income | $26,136 | |
Sources Combined child support income (opens in a new tab) 1.1.C.190
This divides each parent's child support income by the combined figure, giving each parent's percentage share of the combined income, which is the share of the children's costs the formula expects that parent to meet.
| You | Other parent | |
|---|---|---|
| Child support income ÷ $26,136 | $19,599 | $6,537 |
| Income percentage | 74.99% | 25.01% |
Sources Income percentage (opens in a new tab) 1.1.I.30
This turns the care each parent provides into a percentage of the time, worked out separately for every child. It is the measure of care the next step converts into a share of costs.
| You | Other parent | |
|---|---|---|
| Nights per year | 75 | 290 |
| Percentage of care | 20% | 80% |
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts each parent's percentage of care into a cost percentage using a set table of care bands, not a straight proportion. The cost percentage is the share of each child's costs that parent is treated as meeting through care.
| You | Other parent | |
|---|---|---|
| Cost percentage | 24%from 20% care | 76%from 80% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% | 0% |
| 14% to 34% (applies here) | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% (applies here) | 76% |
| 87% to 100% | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This takes each parent's cost percentage away from their income percentage for each child. A positive result shows that parent's care falls short of the share of costs their income points to, a negative result shows it goes beyond that share, and the later steps work out what that means in dollars.
| You | Other parent | |
|---|---|---|
| Income percentage | 74.99% | 25.01% |
| Cost percentage | −24% | −76% |
| Child support percentage | 50.99% | −50.99% |
The other parent's negative percentage means they don't pay child support for Children 1 and 2.
Sources Child support percentage (opens in a new tab) 1.1.C.140
This works out a cost for each child on its own, because a parent has another child support case: the table amount at the parents' combined child support income as if every child in the case were that child's age, divided by the number of children in the case. Children of different ages can therefore get different costs.
| Amount | |
|---|---|
| Cost of 2 children, all 13 or over | $7,579 |
| Per child | $3,790 |
| Amount | |
|---|---|
| Cost of 2 children, all under 13 | $6,273 |
| Per child | $3,137 |
This is the average amount spent raising your children at your combined income, not the amount you pay.
Sources Costs of the child (opens in a new tab) 1.1.C.210
This multiplies each child's cost by the paying parent's child support percentage to give the amount the ordinary formula would charge for that child, before the multi-case cap is checked.
| Your child support payable | |
|---|---|
| F1 Step 6 × Step 1A | |
| Child 1 | $1,93350.99% × $3,790 |
| Child 2 | $1,60050.99% × $3,137 |
Sources Annual rate (opens in a new tab) 1.1.A.70
This works out a ceiling for each child, so a parent with other cases is not asked to pay more for a child than if all their children lived together: the child's cost at the paying parent's own income with the children from all of that parent's child support cases counted, less the share of that cost the parent already meets through care. Where the ceiling is lower than the formula amount, it becomes the rate.
| Your multi-case cap | |
|---|---|
| Child 1 | $1,746$2,297 × 76% |
| Child 2 | $1,473$1,938 × 76% |
Sources Multi-case cap (opens in a new tab) 1.1.M.40
For each child this takes the lower of the formula amount and the multi-case cap, and adds the children's amounts together.
| Your annual rate | |
|---|---|
| Lower of Step 1B and Step 2 | |
| Child 1 | $1,746 · Capped |
| Child 2 | $1,473 · Capped |
| Total | $3,219 |
Sources Annual rate (opens in a new tab) 1.1.A.70
Guide example: DSS Child Support Guide 2.2.4, “Example — Using 2024 rates”
Formula 4
2025 rates
DSS Formula 4 example
Aliya and Edmund have two children. Kristina, aged 13 plus, lives with Edmund, and Harriette, aged 0 to 12, lives with a grandparent. Aliya also has a child in a second child support case and a relevant dependent child.
| Payment | DSS guide | Calculator | Difference |
|---|---|---|---|
| Aliya pays Edmund | $1,342 | $1,342 | None |
| Aliya pays the grandparent | $1,132 | $1,132 | None |
| Edmund pays the grandparent | $4,791 | $4,792 | $1 |
The guide’s worked steps show $4,791 for Edmund’s payment ($6,158 × 77.81%), and the calculator returns $4,792. That multiplication comes to $4,791.54, and section 156 of the Child Support (Assessment) Act rounds amounts to the nearest whole dollar. The guide’s summary line prints $4,819, the multi-case cap from its Step 2.
See the full breakdown
The case
- Aliya’s income
- $45,000
- Edmund’s income
- $70,000
- Children in this case
- Kristina, aged 13 plus, and Harriette, aged 0 to 12
- Care
- Kristina lives with Edmund; Harriette lives with the grandparent
- Aliya also has
- One child aged 0 to 12 in another case, and one relevant dependent child aged 0 to 12
The breakdown is shown from Aliya’s side, so Aliya appears as “You”.
Result breakdown
Formula 4: Multiple child support cases with a non-parent carer
Formula 4 applies because a non-parent carer has qualifying care and at least one parent has children in another child support assessment.
This takes each parent's adjusted taxable income and sets aside a self-support amount, plus any allowance for other children they support, leaving the child support income the formula works with.
| You | Other parent | |
|---|---|---|
| Adjusted taxable income | $45,000 | $70,000 |
| Self-support amount | −$29,841 | −$29,841 |
| Relevant dependent child amount | −$2,577 | — |
| Multi-case allowance | −$1,132 | — |
| Child support income | $11,450 | $40,159 |
Sources Child support income (opens in a new tab) 1.1.C.120Self-support amount (opens in a new tab) 1.1.S.20Relevant dependent child amount (opens in a new tab) 3.1.2Multi-case allowance (opens in a new tab) 1.1.M.30
This adds both parents' child support incomes into one combined figure, which is used to read the children's cost from the table and to measure each parent's share of the income.
| You | Other parent | |
|---|---|---|
| Child support income | $11,450 | $40,159 |
| Combined child support income | $51,609 | |
Sources Combined child support income (opens in a new tab) 1.1.C.190
This divides each parent's child support income by the combined figure, giving each parent's percentage share of the combined income, which is the share of the children's costs the formula expects that parent to meet.
| You | Other parent | |
|---|---|---|
| Child support income ÷ $51,609 | $11,450 | $40,159 |
| Income percentage | 22.19% | 77.81% |
Sources Income percentage (opens in a new tab) 1.1.I.30
This turns the care each parent and the non-parent carer provides into a percentage of the time, worked out for every child. The parents' percentages are shown here and feed the next step; the carer's is carried to the final step, where it can be used to divide a rate that is shared.
| You | Other parent | |
|---|---|---|
| Nights per year | 0 | 365 |
| Percentage of care | 0% | 100% |
| You | Other parent | |
|---|---|---|
| Nights per year | 0 | 0 |
| Percentage of care | 0% | 0% |
Care differs between the children, so each child is calculated separately from here.
Sources Percentage of care (opens in a new tab) 1.1.P.70
This converts each parent's percentage of care into a cost percentage using a set table of care bands, not a straight proportion: the share of each child's costs that parent is treated as meeting through care. The non-parent carer's cost percentage is worked out the same way and can be used at the final step when a rate is shared.
| You | Other parent | |
|---|---|---|
| Cost percentage | 0%from 0% care | 100%from 100% care |
| You | Other parent | |
|---|---|---|
| Cost percentage | 0%from 0% care | 0%from 0% care |
Care and cost percentage table
| Care | Cost percentage |
|---|---|
| 0% to 13% (applies here) | 0% |
| 14% to 34% | 24% |
| 35% to 47% | 25% plus 2% for each percentage point over 35% |
| 48% to 52% | 50% |
| 53% to 65% | 51% plus 2% for each percentage point over 53% |
| 66% to 86% | 76% |
| 87% to 100% (applies here) | 100% |
Sources Cost percentage (opens in a new tab) 1.1.C.200
This takes each parent's cost percentage away from their income percentage for each child. A positive result shows that parent's care falls short of the share of costs their income points to, a negative result shows it goes beyond that share, and the later steps work out what that means in dollars.
| You | Other parent | |
|---|---|---|
| Income percentage | 22.19% | 77.81% |
| Cost percentage | 0% | −100% |
| Child support percentage | 22.19% | −22.19% |
| You | Other parent | |
|---|---|---|
| Income percentage | 22.19% | 77.81% |
| Cost percentage | 0% | 0% |
| Child support percentage | 22.19% | 77.81% |
The other parent's negative percentage means they don't pay child support for Child 1.
Sources Child support percentage (opens in a new tab) 1.1.C.140
This works out a cost for each child on its own, because a parent has another child support case: the table amount at the parents' combined child support income as if every child in the case were that child's age, divided by the number of children in the case. Children of different ages can therefore get different costs.
| Amount | |
|---|---|
| Cost of 2 children, all 13 or over | $14,898 |
| Per child | $7,449 |
| Amount | |
|---|---|
| Cost of 2 children, all under 13 | $12,318 |
| Per child | $6,159 |
This is the average amount spent raising your children at your combined income, not the amount you pay.
Sources Costs of the child (opens in a new tab) 1.1.C.210
This multiplies each child's cost by each paying parent's child support percentage to give the amount the ordinary formula would charge for that child, before the multi-case cap is checked.
| You | Other parent | |
|---|---|---|
| F1 Step 6 × Step 2A | ||
| Child 1 | $1,65322.19% × $7,449 | No child support payable |
| Child 2 (non-parent carer) | $1,36722.19% × $6,159 | $4,79277.81% × $6,159 |
Sources Annual rate (opens in a new tab) 1.1.A.70
This works out a ceiling for each child, so a parent with other cases is not asked to pay more for a child than if all their children lived together: the child's cost at the paying parent's own income with the children from all of that parent's child support cases counted, less the share of that cost the parent already meets through care. Where the ceiling is lower than the formula amount, it becomes the rate.
| You | Other parent | |
|---|---|---|
| Child 1 | $1,342$1,342 × 100% | No multi-case cap |
| Child 2 (non-parent carer) | $1,132$1,132 × 100% | No multi-case cap |
Sources Multi-case cap (opens in a new tab) 1.1.M.40
For each child this takes the lower of the formula amount and the multi-case cap, and each amount goes to whoever is entitled to receive it for that child.
| You | Other parent | |
|---|---|---|
| Lower of Step 2B and Step 3 | ||
| Child 1 | $1,342 · Capped | No annual rate |
| Child 2 (non-parent carer) | $1,132 · Capped | $4,792Step 2B |
Payments
- You pay the other parent$1,342
- You pay the non-parent carer$1,132
- Other parent pays the non-parent carer$4,792
Sources Annual rate (opens in a new tab) 1.1.A.70
Guide example: DSS Child Support Guide 2.2.5, “Example: Using 2025 rates”
Sources
- Assessment year: 2026. Self-support amount: $31,046.
- Costs of Children source: Registered 2026 Costs of the Children Table Notice.
- Formula rules: the Child Support (Assessment) Act 1989 and the DSS Child Support Guide sections linked on each example.
- The DSS guide examples use the 2024 and 2025 values the guide used, not the 2026 values.
This page is general information about how an estimate is calculated. It is not legal or financial advice, and an estimate is not an official assessment.
Frequently asked questions
What are the six Australian child support formulas?
Australian child support uses six formulas: Formula 1 (basic single case), Formula 2 (single case with a non-parent carer), Formula 3 (multiple child support cases), Formula 4 (multiple cases with a non-parent carer), Formula 5 (one-parent income assessment, used when a parent is overseas in a non-reciprocating jurisdiction), and Formula 6 (one-parent income assessment with a deceased parent). The correct formula is selected from the case details.
Can a calculator handle multi-case (Formula 3) child support?
Yes. In the Formula 3 example on this page, the calculator deducts a multi-case allowance of $3,622 for Parent B, works out the costs of the children under the multi-case rules, and returns $10,346 per year.
Can a child support calculator use different care for each child?
AusChildSupport can. Each child in an assessment has its own care arrangement, and the calculator works out a separate care, cost and child support percentage per child before combining them.