Proof pageFormula 1-6 · 2026 assessment year · source citations included
Australian Child Support Formula 1-6 Calculator Examples
A clean set of worked examples for the six Australian child support formula paths. Each exhibit records the exact inputs, the formula pathway, the annual result, a live AusChildSupport result screenshot, and the relevant DSS Child Support Guide citation.
Formula 1-6 proof
Six worked formula exhibits
These examples are calculator-derived estimates for the 2026assessment year. They are not Services Australia assessments, government endorsement, legal advice, or a promise that every possible fact pattern has the same result.
Parent A pays Parent B $6,843.24 per year.
Formula path
Formula 1 is the basic single-case assessment. It applies when only the two parents care for the children and neither parent has a child in another child support case or a relevant dependent child that changes the result.
Exact inputs
Parent A — adjusted taxable income
$120,000
Parent B — adjusted taxable income
$100,000
Children
Three (two aged 0–12, one aged 13+ years)
Care (Parent A)
160 nights per year (Parent B 205 nights)
Relevant dependants / other cases
None
Inspect the calculationWorked steps and DSS source citation
How the result is built
- Child support income: A = 120,000 − 31,046 = 88,954; B = 100,000 − 31,046 = 68,954.
- Combined child support income = 157,908. Income percentage for A = 88,954 ÷ 157,908 = 56.33%.
- Care 160 ÷ 365 = 43.8% → rounds to 43% care → 41% cost. A’s child support percentage = 56.33 − 41 = 15.33%.
- Costs of the children (mixed-age table, three children at 157,908) = $44,639.53.
- Annual rate = 15.33% × 44,639.53 = $6,843.24.
Source citation: DSS Child Support Guide 2.2.2. The screenshot records the calculator output; the text keeps the inputs and result inspectable without relying on the image alone.
Live result: $6,843.24/yr, labelled Formula 1 — Basic Formula, with each child’s care percentage and every worked step expanded.
View full ↗Both parents pay the non-parent carer — a combined $7,341.28 per year.
Formula path
Formula 2 applies when a non-parent carer — for example a grandparent — has at least 35% care of a child, and neither parent has a child in another child support case. Both parents can be liable to the carer.
Exact inputs
Parent A — adjusted taxable income
$90,000
Parent B — adjusted taxable income
$60,000
Children
One (aged 0–12)
Care (per fortnight)
Parent A 3 · Parent B 2 · Non-parent carer 9
Inspect the calculationWorked steps and DSS source citation
How the result is built
- Child support income: A = 90,000 − 31,046 = 58,954; B = 60,000 − 31,046 = 28,954.
- The non-parent carer has 9 of 14 nights = 65% care (76% cost), so the carer is an eligible carer for the assessment.
- Each parent’s child support percentage is positive (income share above their low cost share), so each parent is liable to the carer rather than to each other.
- Parent-to-parent payment is $0; the combined liability is directed to the carer: $6,079.15 + $1,262.14 = $7,341.28.
Source citation: DSS Child Support Guide 2.2.3. The screenshot records the calculator output; the text keeps the inputs and result inspectable without relying on the image alone.
Live result: Formula 2 — Single Case With A Non-Parent Carer. Both parents pay the carer ($6,079.15 + $1,262.14 = $7,341.28/yr), every step expanded.
View full ↗Parent A pays Parent B $5,659.42 per year.
Formula path
Formula 3 is used in multi-case situations, where one or both parents have child support responsibilities in more than one case. It applies a multi-case allowance, child-specific (same-age) costs, and a multi-case cap on the annual rate.
Exact inputs
Parent A — adjusted taxable income
$120,000 (plus 1 relevant dependent child, 0–12)
Parent B — adjusted taxable income
$100,000 (plus a second child support case, 1 child 0–12)
Children in this case
Three (two aged 0–12, one aged 13+ years)
Care (per fortnight)
Parent A 6 nights (Parent B 8 nights)
Inspect the calculationWorked steps and DSS source citation
How the result is built
- Relevant dependent child amount for Parent A = $14,274.75, so CSI_A = 120,000 − 31,046 − 14,274.75 = $74,679.25.
- Multi-case allowance for Parent B = $4,599 (shown as a line item), so CSI_B = 68,954 − 4,599 = $64,355.
- Combined child support income = $139,034.25. Income percentage for A = 53.71%.
- Care 6 of 14 = 42.9% → 42% care → 39% cost. A’s child support percentage = 14.71%.
- Costs are computed with the multi-case same-age method (Act s55HA), giving an annual rate of $5,659.42.
Source citation: DSS Child Support Guide 2.2.4. The screenshot records the calculator output; the text keeps the inputs and result inspectable without relying on the image alone.
Live result: Formula 3 — Multiple Child Support Cases, $5,659.42/yr, every step expanded. The breakdown lists the relevant-dependent-child amount and the multi-case allowance as explicit line items.
View full ↗Both parents pay the non-parent carer — a combined $7,070.31 per year.
Formula path
Formula 4 applies when a non-parent carer is involved and one or both parents also have other child support cases. It combines the non-parent-carer rules with the multi-case allowance and cap.
Exact inputs
Parent A — adjusted taxable income
$90,000
Parent B — adjusted taxable income
$60,000 (plus a second child support case, 1 child 0–12)
Children in this case
One (aged 0–12)
Care (per fortnight)
Parent A 3 · Parent B 2 · Non-parent carer 9
Inspect the calculationWorked steps and DSS source citation
How the result is built
- Child support income: A = 90,000 − 31,046 = 58,954.
- Parent B has a second case, so a multi-case allowance of $3,474 is deducted: CSI_B = 28,954 − 3,474 = $25,480.
- The non-parent carer has 9 of 14 nights = 65% care, so both parents are liable to the carer.
- The breakdown shows a Formula 4 calculation block with the multi-case cap step before the payment to the carer ($6,230.03 + $840.28 = $7,070.31).
Source citation: DSS Child Support Guide 2.2.5. The screenshot records the calculator output; the text keeps the inputs and result inspectable without relying on the image alone.
Live result: Formula 4 — Multiple Cases With A Non-Parent Carer. Both parents pay the carer ($6,230.03 + $840.28 = $7,070.31/yr), with the multi-case cap step and every step expanded.
View full ↗Parent A pays the non-parent carer $5,880.32 per year.
Formula path
Formula 5 applies when a non-parent carer applies for an assessment and only one parent’s income can be assessed — usually because the other parent lives overseas in a non-reciprocating jurisdiction. The available parent’s income is used, with a doubling-then-halving adjustment.
Exact inputs
Available parent (A) — adjusted taxable income
$80,000
Other parent
Overseas, non-reciprocating (details not required)
Children
One (aged 0–12)
Care (per fortnight)
Parent A 4 · Non-parent carer 10
Inspect the calculationWorked steps and DSS source citation
How the result is built
- Only the available parent’s income is assessable: CSI_A = 80,000 − 31,046 = $48,954.
- The method recognises the child has two parents by doubling the available income for the cost lookup, then halving the resulting rate.
- The breakdown includes a distinct “halved annual rate” step, confirming the Formula 5 method.
- The non-parent carer has 10 of 14 nights, so the available parent pays the carer $5,880.32/yr.
Source citation: DSS Child Support Guide 2.2.6. The screenshot records the calculator output; the text keeps the inputs and result inspectable without relying on the image alone.
Live result: Formula 5 — One-Parent Income Assessment, $5,880.32/yr, every step expanded — including a visible halved annual rate step.
View full ↗Parent A pays the non-parent carer $6,288.81 per year.
Formula path
Formula 6 applies when a non-parent carer applies and one parent is deceased. Only the surviving parent’s income is used — without the doubling-and-halving step used in Formula 5.
Exact inputs
Surviving parent (A) — adjusted taxable income
$80,000
Other parent
Deceased (details not required)
Children
One (aged 0–12)
Care (per fortnight)
Parent A 4 · Non-parent carer 10
Inspect the calculationWorked steps and DSS source citation
How the result is built
- Only the surviving parent’s income is used: CSI_A = 80,000 − 31,046 = $48,954.
- Unlike Formula 5, the income is not doubled and the rate is not halved — there is no “halved annual rate” step.
- Because the single income is used directly, the result on the same inputs is higher than Formula 5.
- The non-parent carer has 10 of 14 nights, so the surviving parent pays the carer $6,288.81/yr.
Source citation: DSS Child Support Guide 2.2.7. The screenshot records the calculator output; the text keeps the inputs and result inspectable without relying on the image alone.
Live result: Formula 6 — One-Parent Income Assessment With A Deceased Parent, $6,288.81/yr, every step expanded. No halved-rate step (single income used directly).
View full ↗Official guide cross-checks
DSS guide examples run through the calculator
The DSS Child Support Guide publishes worked examples for Formula 1, Formula 3 and Formula 4 using earlier assessment-year values. These cards keep the guide fact patterns and show the output from this site's actual 2026 calculator, with the same screenshot treatment as the six formula exhibits above.
These are calculator estimates from DSS guide fact patterns, not official Services Australia assessments and not official DSS-published 2026 worked examples.
Parent B pays Parent A $4,708.83 per year.
DSS fact pattern
Mark and Lisette have three children: Domitilla, 9, Delia, 7, and Helen, 5. The children spend 290 nights a year with Mark and 75 nights with Lisette. Mark has adjusted taxable income of $50,000 and Lisette has adjusted taxable income of $60,000.
What the DSS guide publishes
The guide's published Formula 1 example uses 2025 values and ends with Lisette paying Mark $4,863 per year.
Calculator inputs
Parent A / Mark — adjusted taxable income
$50,000
Parent B / Lisette — adjusted taxable income
$60,000
Children
Three children aged 9, 7 and 5
Care
Parent A 290 nights/year · Parent B 75 nights/year
Relevant dependants / other cases
None
Inspect the calculator cross-checkWorked steps and assessment-year note
How the calculator built it
- The calculator keeps the DSS incomes and care pattern, then applies 2026 values: self-support amount $31,046.
- Child support income: Parent A = $18,954; Parent B = $28,954; combined child support income = $47,908.
- Income percentages: Parent A 39.56%, Parent B 60.44%. Parent A has 80% care, so Parent B's child support percentage is 36.44%.
- The 2026 cost of each child is $4,307.38, so Parent B's liability is $1,569.61 per child.
- Total annual rate = $1,569.61 x 3 = $4,708.83.
The DSS page is the source fact pattern. The screenshot and figures here are from the AusChildSupport calculator using the 2026 assessment-year constants.
Live calculator result for the DSS Formula 1 fact pattern: Parent B pays Parent A $4,708.83/yr, with the calculator breakdown expanded.
View full ↗Parent A pays Parent B $2,833 per year.
DSS fact pattern
In case 1, Vincent (adjusted taxable income $50,000) and Faith ($35,000) have two children — Geraldine, 14, and Thomas, 10. In case 2, Vincent has a third child, Honoria, 5, in a separate child support case. Vincent cares for the case-1 children 75 nights a year (Faith has the other 290). Neither parent has a relevant dependent child, and Faith has no other case.
What the DSS guide publishes
The guide's published worked example uses 2024 values and ends with Vincent paying Faith $3,219 per year.
Calculator inputs
Parent A / Vincent — adjusted taxable income
$50,000
Parent B / Faith — adjusted taxable income
$35,000
Children in this case
Geraldine, 14, and Thomas, 10
Care
Parent A 75 nights/year · Parent B 290 nights/year
Parent A other child support case
Honoria, 5
Inspect the calculator cross-checkWorked steps and assessment-year note
How the calculator built it
- The calculator keeps the DSS incomes, ages and care pattern, then applies 2026 values.
- Parent A's multi-case allowance for Honoria is $1,706, so child support income is $17,248. Parent B's child support income is $3,954.
- Combined child support income is $21,202. Income percentages are Parent A 81.35% and Parent B 18.65%.
- Parent A has 20% rounded care and 24% cost, so Parent A's child support percentage is 57.35%.
- The multi-case cap binds on both children: $1,537 for Geraldine and $1,296 for Thomas, giving $2,833 per year.
The calculator output matches the earlier text-only recalc, but the page now shows it as a live calculator-worked example with the result screenshot.
Live calculator result for the DSS Formula 3 fact pattern: Parent A pays Parent B $2,833/yr, with the multi-case allowance and cap visible in the expanded breakdown.
View full ↗Parent A pays Parent B $1,235 per year, and the non-parent carer receives $5,704.86 per year combined.
DSS fact pattern
In case 1, Aliya (adjusted taxable income $45,000) and Edmund ($70,000) have two children — Kristina, 14, and Harriette, 10. Edmund has sole (100%) care of Kristina, while Harriette lives full-time with her grandparent, who has applied for a child support assessment as a non-parent carer. Aliya also has a second child support case (Claudia, 7) and a relevant dependent child with her new partner (Louisa, 4).
What the DSS guide publishes
The guide's published worked example uses 2025 values: Aliya pays Edmund $1,342 for Kristina and the grandparent $1,132 for Harriette, and Edmund pays the grandparent about $4,819 for Harriette.
Calculator inputs
Parent A / Aliya — adjusted taxable income
$45,000
Parent B / Edmund — adjusted taxable income
$70,000
Children in this case
Kristina, 14, and Harriette, 10
Care
Kristina: Parent B 365 nights/year. Harriette: grandparent 365 nights/year.
Parent A adjustments
Other case child Claudia, 7; relevant dependent child Louisa, under 13
Inspect the calculator cross-checkWorked steps and assessment-year note
How the calculator built it
- The calculator keeps the DSS incomes, ages, care pattern, relevant dependent child and other-case child, then applies 2026 values.
- Parent A's relevant-dependent-child amount is $2,372.18 and multi-case allowance is $1,042, leaving child support income of $10,539.82.
- Parent B's child support income is $38,954. Combined child support income is $49,493.82.
- For Kristina, Parent A's liability is capped at $1,235 and payable to Parent B.
- For Harriette, Parent A pays the grandparent $1,042 and Parent B pays the grandparent $4,662.86.
The result comes from the site's calculator for the DSS Formula 4 fact pattern. It preserves the separate parent-to-parent and parent-to-carer payment lines instead of compressing the case into one number.
Live calculator result for the DSS Formula 4 fact pattern: Parent A pays Parent B $1,235/yr; the grandparent receives $1,042 from Parent A and $4,662.86 from Parent B.
View full ↗Methodology
How these examples were produced
Each scenario was entered into the live AusChildSupport calculator and run. The figures shown in each screenshot are the calculator's own output for those inputs; the examples use 2026 assessment-year values.
Reproducibility
- Assessment year: 2026. Self-support amount: $31,046.
- Costs of Children source: Registered 2026 Costs of the Children Table Notice.
- Each example was verified against the formula the calculator selected: Formula 1 through Formula 6.
- Sources include the Child Support (Assessment) Act 1989, the DSS Child Support Guide, and Services Australia public guidance.
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.
FAQ
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 this worked example, AusChildSupport applies Formula 3 in one pass: it deducts a $4,599 multi-case allowance, applies the legislated same-age cost method, and returns $5,659.42 per year.
Does AusChildSupport require care to be entered as 6 nights out of 14?
No. The care field accepts a period of Fortnight, Week, Year or Percent. Entering 160 nights per year returns $6,843.24 — the same figure as the Services Australia estimator. The 6-nights-out-of-14 input is one option, not a requirement.
Is 160 nights per year the same as 6 nights per fortnight?
No. 160 nights per year is 43.8% care, which rounds to 43% for the formula. Six nights out of 14 is 42.9% care — about 156 nights per year — which rounds to 42%. They land on different care bands and produce different results, so they are not interchangeable inputs.
Is the multi-case allowance shown or hidden?
It is shown. The breakdown displays the 2026 costs-of-children figures, the multi-case allowance ($4,599 in our Formula 3 example), and the surrounding steps as explicit line items, so the adjustment is auditable rather than handled out of sight.
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.
Run your own scenario
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