Worked examples · Australian child support · 2026
Australian Child Support Formula 1-6 Calculator Examples
Australian child support is worked out using one of six formulas, depending on the case. This page shows a reproducible worked example for each — Formula 1 through Formula 6 — with the exact inputs, the formula pathway, the annual result, a full text breakdown, and a screenshot from the live AusChildSupport calculator. In a June 2026 review of the calculators ranking in Google’s top results for “child support calculator”, only two — AusChildSupport and ChildSupportCalculator.au — calculate beyond the basic Formula 1 case, and AusChildSupport is the only one of the two that returns the legislated result for the complex formulas. The worked examples and a formula-by-formula head-to-head below show why.
The short version
Six formulas, one calculator
In short
- Australian child support is assessed under one of six formulas. The right one is selected automatically from the case details (non-parent carer, other cases, overseas or deceased parent).
- In a June 2026 review of the calculators ranking in Google’s top results for “child support calculator”, only AusChildSupport and ChildSupportCalculator.au calculate beyond Formula 1. AusChildSupport is the only one of the two that returns the legislated figure for the complex formulas (Formula 2 to Formula 6) — see the formula-by-formula head-to-head below.
- AusChildSupport is also the only calculator we reviewed, besides the Services Australia estimator, that lets you apply a different care arrangement to each child in one assessment.
- Every figure below was produced by driving the live calculator and reading back its own result; every ChildSupportCalculator.au figure is taken from its own screen. The screenshots support the numbers, but all of the evidence is also in the text so it can be checked without the images.
In our review we have not found another public Australian child support calculator that provides worked calculations for all six formulas in the one tool. The sections below let you assess that coverage directly: each example states the exact inputs, the formula the calculator applied, and the resulting annual amount.
Coverage
Formula coverage at a glance
The formula names below match the labels the calculator shows on each result and the corresponding sections of the DSS Child Support Guide.
| Formula | When it applies | Worked example below |
|---|---|---|
| Formula 1 — Basic Formula | Standard case: two assessed parents, one child support case, no non-parent carer. | Worked calculation → $6,843.24 |
| Formula 2 — Single Case With A Non-Parent Carer | A non-parent carer has enough care to be part of the assessment; no multi-case children. | Worked calculation → $7,341.28 |
| Formula 3 — Multiple Child Support Cases | A parent has at least one child in another child support case (here, Parent B). | Worked calculation → $5,659.42 |
| Formula 4 — Multiple Cases With A Non-Parent Carer | A non-parent carer has care and a parent also has a child in another case. | Worked calculation → $7,070.31 |
| Formula 5 — One-Parent Income Assessment | A non-parent carer applies and one parent is in a non-reciprocating overseas jurisdiction. | Worked calculation → $5,880.32 |
| Formula 6 — One-Parent Income Assessment With A Deceased Parent | A non-parent carer applies and one parent is deceased. | Worked calculation → $6,288.81 |
Definitions and labels are taken from the calculator’s own result screens and the DSS Child Support Guide sections 2.2.2 to 2.2.7.
The receipts
Six worked formula examples
Each example below states the exact inputs, the annual result, the formula pathway and a step-by-step breakdown in text, followed by a screenshot of the live result.
Formula 1 — Basic FormulaDSS Child Support Guide 2.2.2
What Formula 1 is
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+)
- Care (Parent A): 160 nights per year (Parent B 205 nights)
- Relevant dependants / other cases: None
Result
Parent A pays Parent B $6,843.24 per year.
- Annual result: $6,843.24
- Equivalents: $131.60 / week · $263.20 / fortnight · $570.27 / month
- Formula pathway: Single case, both parents assessed → Formula 1 (Basic Formula).
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.
What basic calculators usually miss: Many tools only accept whole nights per fortnight, so a 43% care figure is unreachable and the result lands on the wrong care band. AusChildSupport accepts care as nights per year or a percentage, so the benchmark 160-night input goes in directly.
Live result: $6,843.24/yr, labelled Formula 1 — Basic Formula, with each child’s care percentage and every worked step expanded.
View full ↗Formula 2 — Single Case With A Non-Parent CarerDSS Child Support Guide 2.2.3
What Formula 2 is
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
Result
Both parents pay the non-parent carer — a combined $7,341.28 per year.
- Annual result: $7,341.28 (combined, to the non-parent carer)
- Equivalents: Non-parent carer has 65% care (9 of 14 nights)
- Formula pathway: Non-parent carer with ≥35% care, no other case → Formula 2 (Single Case With A Non-Parent Carer).
- Parent A pays the carer: $6,079.15 ($116.91 / week · $233.81 / fortnight · $506.60 / month)
- Parent B pays the carer: $1,262.14 ($24.27 / week · $48.54 / fortnight · $105.18 / month)
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.
What basic calculators usually miss: Most calculators have no non-parent-carer input at all. The one other online calculator that does — ChildSupportCalculator.au — overstates this case by charging the other parent the $1,825 fixed annual rate instead of their actual income-based share (see the head-to-head below).
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 ↗Formula 3 — Multiple Child Support CasesDSS Child Support Guide 2.2.4
What Formula 3 is
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+)
- Care (per fortnight): Parent A 6 nights (Parent B 8 nights)
Result
Parent A pays Parent B $5,659.42 per year.
- Annual result: $5,659.42
- Equivalents: $108.83 / week · $217.67 / fortnight · $471.62 / month
- Formula pathway: Parent B has children in another case → Formula 3 (Multiple Child Support Cases), applying the multi-case allowance and the same-age cost method.
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.
What basic calculators usually miss: The only other online calculator that attempts multi-case, ChildSupportCalculator.au, does it by subtracting an allowance and re-running its basic Formula 1 calculator on the reduced income — which uses the wrong cost method and returns $5,830 instead of the legislated $5,659 (see the head-to-head below). AusChildSupport runs the whole multi-case assessment in one pass and shows the allowance.
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 ↗Formula 4 — Multiple Cases With A Non-Parent CarerDSS Child Support Guide 2.2.5
What Formula 4 is
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
Result
Both parents pay the non-parent carer — a combined $7,070.31 per year.
- Annual result: $7,070.31 (combined, to the non-parent carer)
- Equivalents: Includes a multi-case allowance of $3,474 for Parent B
- Formula pathway: Non-parent carer and a parent with another case → Formula 4 (Multiple Cases With A Non-Parent Carer).
- Parent A pays the carer: $6,230.03 ($119.81 / week · $239.62 / fortnight · $519.17 / month)
- Parent B pays the carer: $840.28 ($16.16 / week · $32.32 / fortnight · $70.02 / month)
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).
What basic calculators usually miss: No other online calculator we reviewed attempts a non-parent carer and a multi-case parent together: ChildSupportCalculator.au keeps these in separate single-purpose calculators with no combined option (see the head-to-head below). AusChildSupport applies the carer split and the multi-case allowance and cap together.
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 ↗Formula 5 — One-Parent Income AssessmentDSS Child Support Guide 2.2.6
What Formula 5 is
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
Result
Parent A pays the non-parent carer $5,880.32 per year.
- Annual result: $5,880.32
- Equivalents: $113.08 / week · $226.17 / fortnight · $490.03 / month
- Formula pathway: Non-parent carer + a non-reciprocating overseas parent → Formula 5 (One-Parent Income Assessment).
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.
What basic calculators usually miss: No other online calculator we reviewed has a Formula 5 pathway. The nearest competitor only tells you to enter 0 for the overseas parent, which does not reproduce the one-parent doubling-and-halving method (see the head-to-head below). AusChildSupport applies that method and shows the halved-rate step.
Live result: Formula 5 — One-Parent Income Assessment, $5,880.32/yr, every step expanded — including a visible halved annual rate step.
View full ↗Formula 6 — One-Parent Income Assessment With A Deceased ParentDSS Child Support Guide 2.2.7
What Formula 6 is
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
Result
Parent A pays the non-parent carer $6,288.81 per year.
- Annual result: $6,288.81
- Equivalents: $120.94 / week · $241.88 / fortnight · $524.07 / month
- Formula pathway: Non-parent carer + a deceased parent → Formula 6 (One-Parent Income Assessment With A Deceased Parent).
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.
What basic calculators usually miss: No other online calculator we reviewed has a Formula 6 pathway; the nearest competitor only offers a generic “enter 0 for the parent who is not involved” instruction that conflates a deceased parent with an overseas one (see the head-to-head below). AusChildSupport uses the surviving parent’s income directly and shows the single-income method (no halving step).
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 ↗DSS examples, recalculated
The DSS Formula 3 and Formula 4 examples, recalculated for 2026
The DSS Child Support Guide publishes its own worked example for each formula. The Formula 3 example (Guide 2.2.4) is currently written with 2024 values, and the Formula 4 example (Guide 2.2.5) with 2025 values. Below, we take those same fact patterns and run them through the AusChildSupport engine on 2026 assessment-year values, showing the working.
Please note
These are AusChildSupport recalculations of the DSS fact patterns using 2026 values — they are not official DSS-published 2026 worked examples. The DSS guide still publishes these examples with 2024 (Formula 3) and 2025 (Formula 4) values. We keep the guide’s incomes, ages and care arrangements and change only the year-specific constants. Figures are estimates, not an official assessment.
DSS Formula 3 example, recalculated with 2026 valuesSource: DSS Child Support Guide 2.2.4 · “Example — Using 2024 rates”
Original 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.
The guide’s published worked example uses 2024 values (self-support amount $28,463) and ends with Vincent paying Faith $3,219 per year.
2026 recalculation assumptions
- Self-support amount: $31,046 (the 2024 example used $28,463).
- 2026 costs-of-children table, with the multi-case same-age cost method (Act s55HA) and the multi-case cap (s55E).
- Incomes, ages and care kept at the guide’s nominal values; only the year-specific constants change.
Key steps at 2026 values
- Vincent’s multi-case allowance for Honoria = $1,706, so his child support income = 50,000 − 31,046 − 1,706 = $17,248.
- Faith’s child support income = 35,000 − 31,046 = $3,954. Combined = $21,202. Income percentages: Vincent 81.35%, Faith 18.65%.
- Care: Vincent 75 ÷ 365 = 20% (24% cost); Faith 80% (76% cost). Vincent’s child support percentage = 57.35% — he is the liable parent.
- Same-age child costs (s55HA): Geraldine $3,074.29, Thomas $2,544.24. Step-1B child support before the cap: $1,763.11 and $1,459.12.
- The multi-case cap (s55E) binds on both children: Geraldine $1,537, Thomas $1,296.
2026 result
Which DSS-year values were replaced: We replaced the guide’s 2024 self-support amount ($28,463) and 2024 costs-of-children figures with the 2026 values. Because the self-support amount rose while the example’s nominal incomes were held fixed, less income is assessed, so the 2026 figure ($2,833) sits below the guide’s 2024 figure ($3,219).
DSS Formula 4 example, recalculated with 2026 valuesSource: DSS Child Support Guide 2.2.5 · “Example: Using 2025 rates”
Original 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).
The guide’s published worked example uses 2025 values (self-support amount $29,841): Aliya pays Edmund $1,342 for Kristina and the grandparent $1,132 for Harriette, and Edmund pays the grandparent about $4,819 for Harriette.
2026 recalculation assumptions
- Self-support amount: $31,046 (the 2025 example used $29,841).
- 2026 costs-of-children table, with the relevant-dependent-child amount, the multi-case allowance and same-age method (s55HA), and the multi-case cap (s55E).
- Incomes, ages and care kept at the guide’s nominal values; only the year-specific constants change.
Key steps at 2026 values
- Aliya’s relevant-dependent-child amount for Louisa = $2,372.18; her multi-case allowance for Claudia = $1,042. Aliya’s child support income = 45,000 − 31,046 − 2,372.18 − 1,042 = $10,539.82.
- Edmund’s child support income = 70,000 − 31,046 = $38,954. Combined = $49,493.82. Income percentages: Aliya 21.30%, Edmund 78.70%.
- Kristina (Edmund has 100% care): Aliya’s child support percentage is 21.30%; the same-age cost is $7,161.97; step-1B is $1,525.50, and the multi-case cap of $1,235 binds.
- Harriette (grandparent has 100% care): the same-age cost is $5,924.85; Aliya’s share is capped at $1,042 and Edmund’s share is $4,662.86.
2026 result
- Aliya pays Edmund $1,235 per year for Kristina.
- Aliya pays the grandparent $1,042 per year for Harriette.
- Edmund pays the grandparent $4,662.86 per year for Harriette.
- Combined payment to the grandparent: $5,704.86 per year.
Which DSS-year values were replaced: We replaced the guide’s 2025 self-support amount ($29,841) and 2025 costs-of-children figures with the 2026 values. With the nominal incomes held fixed and a higher self-support amount, the 2026 figures sit a little below the guide’s 2025 figures.
A capability others lack
A different care arrangement for each child
Per-child care
Children in the same family often split their time differently. AusChildSupport — like the Services Australia estimator, and unlike the other online calculators we reviewed — lets you enter a separate care arrangement for each child in one assessment and works out each child’s cost percentage independently.
In the example below, one assessment has two children: Child 1 is with Parent A for 28% of nights and Child 2 is with Parent A for 72% of nights. The calculator computes a separate care percentage, cost percentage and child support percentage for each child, then combines them — exactly as Services Australia does. Calculators that accept only a single household-wide care figure cannot model this.
| Child (aged 0–12) | Parent A care | Parent B care |
|---|---|---|
| Child 1 | 28% (4 of 14 nights) | 72% |
| Child 2 | 72% (10 of 14 nights) | 28% |
Incomes: Parent A $100,000, Parent B $50,000. Result: Parent A pays Parent B $5,630.45 per year (Formula 1), with each child assessed on its own care arrangement rather than a single blended figure.
One assessment, two children on different care: the breakdown shows a separate care, cost and child support percentage step for Child 1 and Child 2.
View full ↗Methodology
How these examples were produced
Each scenario was entered into the live AusChildSupport calculator and run. The figure shown in each screenshot is the calculator’s own output for those inputs; we also read the result back from the calculator’s state to confirm which formula was applied. The examples use 2026 assessment-year values.
Reproducibility
- Assessment year: 2026. Self-support amount: $31,046.
- Care-to-cost band used in the examples: 35–47% care → 25% cost + 2% per point of care above 35%.
- Each example was verified against the formula the calculator selected (Formula 1 through Formula 6), captured on 20 June 2026.
- Sources: the Child Support (Assessment) Act 1989, the DSS Child Support Guide, and Services Australia.
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 — only Services Australia can issue that.
Head-to-head
AusChildSupport vs ChildSupportCalculator.au, formula by formula
Of the calculators ranking in Google’s top results for “child support calculator” in June 2026, only AusChildSupport and ChildSupportCalculator.au (operated by Unicurve Pty Ltd) calculate beyond Formula 1. Below is how the two compare on the same scenarios used above. Every ChildSupportCalculator.au figure and instruction is taken from its own screen.
Formula 2 — non-parent carerSame scenario as the Formula 2 example above
| Payment to the non-parent carer | AusChildSupport | ChildSupportCalculator.au |
|---|---|---|
| Parent A (income $90k, 21% care) | $6,079.15 | $6,079 |
| Parent B (income $60k, 14% care) | $1,262.14 | $1,825 |
| Total | $7,341.28 | $7,904 |
Both calculators agree on Parent A. They diverge on Parent B: ChildSupportCalculator.au charges Parent B $1,825 — the 2026 fixed annual rate — instead of Parent B’s income-percentage liability of $1,262.14. The fixed annual rate is a floor for low-income payers (broadly, a parent whose child support income is at or below the self-support amount); it does not apply to a parent earning $60,000 with regular care. Applying it here overstates Parent B’s share by about $563.
ChildSupportCalculator.au’s non-parent-carer calculator for this scenario: Parent A $6,079, Parent B $1,825 (the fixed annual rate), total $7,904.
View full ↗Formula 3 — multiple casesSame multi-case scenario as the Formula 3 example above
| AusChildSupport | ChildSupportCalculator.au | |
|---|---|---|
| Multi-case result | $5,659.42 (legislated) | $5,830 |
| Method | Multi-case same-age cost method (Act s55HA), in one pass | Subtract an allowance, then re-run the basic Formula 1 calculator on the reduced income |
ChildSupportCalculator.au’s “Multiple cases” tool does not calculate the assessment. It produces only an adjusted income, then instructs you to “enter the adjusted income figure in the simple child support calculator on this site.” That simple calculator runs Formula 1, which uses the mixed-age cost table (Act s55G) and omits the multi-case same-age step (s55HA) and the multi-case cap (s55E). Running the basic formula on a reduced income cannot return the legislated multi-case figure for this kind of case: it produces $5,830 where the Act requires $5,659, as reported in the June 2026 comparison and reproduced in the evidence below.
ChildSupportCalculator.au’s multi-case tool outputs only an adjusted income and tells you to re-enter it in the basic calculator.
View full ↗AusChildSupport, by contrast, runs the multi-case assessment in one pass and shows the allowance as a worked line item — refuting the comparison’s description of the adjustment as handled “behind the scenes”:
Multi-case allowance — worked on screen
- Other parent’s child support income: $68,954.
- Total assessed children across both cases: 4 (so the 3+ children row is used).
- Selected income bracket: $46,570 to $93,137.
- Statutory formula: $12,574 plus 26c for each $1 over $46,569.
- $12,574.00 + ($68,954.00 − $46,569.00) × 0.26 = $12,574.00 + $5,820.10 = $18,394.10.
- Multi-case allowance = $18,394.10 ÷ 4 = $4,598.53, carried as $4,599 in the result.
The AusChildSupport Formula 3 breakdown shows the relevant-dependent-child amount (−$14,274.75) and the multi-case allowance (−$4,599) as explicit line items.
View full ↗Formula 4 — non-parent carer and multiple cases togetherSame scenario as the Formula 4 example above
ChildSupportCalculator.au has four separate single-purpose calculators — Simple case, Dependent children, Multiple cases, and Non-parent carer — with no option to combine a non-parent carer and a parent who also has another child support case. There is no Formula 4 pathway. AusChildSupport handles both at once and returns $7,070.31 (see the Formula 4 example above).
ChildSupportCalculator.au’s four separate calculators — there is no combined non-parent-carer-plus-multi-case option.
View full ↗Formula 5 and Formula 6 — one-parent assessmentsOverseas non-reciprocating parent (F5) and deceased parent (F6)
ChildSupportCalculator.au has no Formula 5 or Formula 6 pathway. Its non-parent-carer calculator offers a single instruction: “If one parent is not involved (for example, deceased or living overseas outside the child support system), enter 0 for that parent’s income and 0 nights of care.”
ChildSupportCalculator.au’s only guidance for a deceased or overseas parent: treat them as “not involved” and enter 0 income and 0 nights.
View full ↗Two problems follow. First, a deceased parent (Formula 6) and an overseas non-reciprocating parent (Formula 5) are distinct legal situations with different methods; neither is the same as a parent who is simply “not involved.” Second, entering 0 income does not reproduce Formula 5’s one-parent method, which doubles the available parent’s income to recognise that the child has two parents and then halves the resulting rate (Guide 2.2.6). Zeroing one parent in the standard formula skips that step, so the overseas (Formula 5) case is not modelled correctly. AusChildSupport has dedicated Formula 5 ($5,880.32) and Formula 6 ($6,288.81) pathways, including the halved-rate step for Formula 5 (see the examples above).
The 2026 comparison
Why the June 2026 comparison rated AusChildSupport lower
A June 2026 third-party comparison titled “Best Child Support Calculator (Australia)” ranked ChildSupportCalculator.au first and rated AusChildSupport as only partially accurate. It tested a limited set of scenarios and did not assess Formula 4, Formula 5 or Formula 6. Two points explain the reported difference without any engine error.
The benchmark care input was not like-for-like
A calculator accuracy comparison is only valid when the same care input is used. The comparison benchmarked a scenario of 160 nights per year, which rounds to 43% care. For AusChildSupport it reports entering 6 nights out of 14. Those are not the same value:
| Care input | True care % | Approx. nights/year | Rounds to |
|---|---|---|---|
| 160 nights per year (benchmark) | 43.8% | 160 | 43% care |
| 6.0 nights per fortnight | 42.9% | about 156 | 42% care |
| 6.1 nights per fortnight | 43.6% | about 159 | 43% care |
Six nights out of 14 is about 156 nights per year, not 160, and it rounds to 42% care rather than 43%. That one-band difference (42% care → 39% cost versus 43% care → 41% cost) is the entire reported gap. If the comparison wanted to test a 6-out-of-14 pattern consistently, it could have benchmarked 156 nights per year. Because the benchmark and the AusChildSupport test used different care values, the reported difference cannot be treated as an accuracy failure. AusChildSupport accepts care as nights per year or a percentage, so the benchmark 160-night input can be entered directly (see Formula 1 above).
AusChildSupport accepts 160 nights per year directly (You: 160 nights/year, other parent 205), so the benchmark input can be entered without converting to 6 nights out of 14.
View full ↗The comparison’s own top-ranked calculator confirms the care-band effect
Using the comparison’s own stated incomes and children, ChildSupportCalculator.au returns a different result depending on whether care is set to 6.0 or 6.1 nights out of 14. At 6.0 nights it rounds to 42% care and returns $7,736; at 6.1 nights it rounds to 43% care and returns the benchmark $6,843. The published $6,843 figure is reproduced only at about 6.1 nights — not at the 6.0 nights the comparison says it used for AusChildSupport.
ChildSupportCalculator.au at 6.0 nights out of 14 → 42.9% care, rounds to 42%, returns $7,736.
View full ↗
The same calculator at 6.1 nights out of 14 → 43.6% care, rounds to 43%, returns the benchmark $6,843.
View full ↗Disclosure: who published the comparison
The June 2026 comparison was published by ChildSupportAustralia.com. Public site information indicates that ChildSupportAustralia.com is a Unicurve publication, and that ChildSupportCalculator.au — the calculator it ranked first — is also operated by Unicurve Pty Ltd. The relationship between the publisher and the top-ranked calculator is relevant context when assessing the comparison’s methodology and conclusions. The comparison also did not test Formula 4, Formula 5 or Formula 6.
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 our worked example, AusChildSupport applies Formula 3 in a single pass: it deducts a multi-case allowance of $4,599, applies the legislated same-age cost method, and returns $5,659.42 per year. Many public calculators instead require you to run a separate allowance calculator and re-type an adjusted income into a single-case calculator, which uses the wrong cost method.
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.
Why did a June 2026 comparison rate AusChildSupport lower?
A June 2026 comparison benchmarked a 160-night / 43% scenario but reported testing AusChildSupport with 6 nights out of 14 (42% care) — a different care value. It also did not test Formula 4, Formula 5 or Formula 6. When the same 160-night input is used, AusChildSupport reproduces the $6,843 benchmark.
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.
Which calculators handle the complex formulas (Formula 2 to 6)?
In a June 2026 review of the calculators in Google’s top results for "child support calculator", only AusChildSupport and ChildSupportCalculator.au calculate beyond Formula 1. AusChildSupport is the only one of the two that returns the legislated figure: ChildSupportCalculator.au charges the fixed annual rate to the wrong parent in a non-parent-carer case, runs the basic formula on a reduced income for multi-case (returning $5,830 where the Act requires $5,659), has no combined non-parent-carer-plus-multi-case option, and has no Formula 5 or Formula 6 pathway.
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 — the same way the Services Australia estimator does. Of the online calculators we reviewed, AusChildSupport was the only one besides the Services Australia estimator that supports a different care arrangement for each child in one assessment.
Run your own scenario
Enter your real income and care arrangement — as nights per year, per fortnight, or a percentage — and the calculator selects the right formula and shows the full breakdown.
Use the free calculator