Child Support Calculator
Estimate child support for a 2026 assessment period from income and care.
Enter the family circumstances
Adjusted taxable income before the self-support deduction.
Adjusted taxable income before the self-support deduction.
Enter A’s care; B has the rest. Switching the entry method resets each child to 20% care.
Other children and cases
Comma-separated ages; blank if none. Once per child per parent.
Your entries stay in this tab. Reloading clears the scenario.
| Component | Parent A | Parent B |
|---|---|---|
| Adjusted taxable income | $61,046.00 | $41,046.00 |
| Self-support deduction | $31,046.00 | $31,046.00 |
| Relevant dependent child allowance | $0.00 | $0.00 |
| Multi-case allowance | $0.00 | $0.00 |
| Child support income | $30,000.00 | $10,000.00 |
| Income percentage | 75% | 25% |
| Child | Annual child cost | A / B care | A / B cost share | A / B child support share | A / B multi-case caps | A / B formula amounts |
|---|---|---|---|---|---|---|
| Child 1, age 8 | $6,800.00 | 20% / 80% | 24% / 76% | 51% / -51% | Not applicable | $3,468.00 / $0.00 |
Without other cases: Parent A pays $3,468.00 annually.
Follow the Child Support Formula
This CS calculator estimates child support under the Australian formula. Child maintenance here means that child-support estimate. Childcare fee subsidies use a separate calculation.
The calculation covers children under 18 cared for by their two parents. Amounts are annual unless labelled otherwise.
Include all children in this parent’s other cases, excluding children in this case.
Qualifying dependants outside support cases; this parent has at least 35% care.
Comma-separated ages, e.g. 4, 10; blank if none. List each child once per parent.
Child support starts with each parent’s adjusted taxable income, less the self-support amount and applicable allowances. Each parent’s remaining income determines their income percentage.
The formula subtracts the cost percentage met through care from that income percentage. A positive difference creates a payment towards the children’s published costs.
For the default example, Parent A earns $61,046 and Parent B earns $41,046. After the $31,046 self-support deduction, their child support incomes are $30,000 and $10,000.
Parent A has 75% of the combined income and 20% care of one eight-year-old. That care meets 24% of costs, leaving a 51% child support share.
The child’s annual cost is 17% of $40,000, or $6,800. Multiplying $6,800 by 51% gives $3,468 a year, equivalent to $66.69 a week.
The calculation uses the DSS costs-of-children tables and 2026 formula values. Costs stop increasing above $232,843 of combined child support income.
Convert Care Nights to Percentages
Care percentage measures time with the child. Cost percentage is the formula’s allowance for costs met through that care. The two percentages are different.
Two nights a fortnight is 14.29% of the fortnight. Over 365 days, that pattern annualises to 52.14 nights.
Select nights and enter 52 whole nights for this example. The calculation is 52 ÷ 365 × 100 = 14.25%, rounded down to 14% care under the official convention.
That care band gives a 24% cost percentage. With the default incomes unchanged, Parent A’s income percentage remains 75% and the annual formula amount stays $3,468.
The income table shows each parent’s income percentage. The child table separates care, cost and child support percentages so you can follow the entered nights through the formula.
For a 365-night period, 73 nights gives 20% care and a 24% cost share. At 128 nights, care rounds to 35% and the cost share becomes 25%.
With the example’s incomes unchanged, 35% care reduces Parent A’s annual formula amount to $3,400. Equal care produces a 50% cost share and a $1,700 amount.
| Care percentage | Nights in 365 days | Cost percentage |
|---|---|---|
| 0 to 13% | 0 to 51 | 0% |
| 14 to 34% | 52 to 127 | 24% |
| 35 to 47% | 128 to 175 | 25%, plus 2 points per care point above 35% |
| 48 to 52% | 176 to 189 | 50% |
| 53 to 65% | 190 to 237 | 51%, plus 2 points per care point above 53% |
| 66 to 86% | 238 to 313 | 76% |
| 87 to 100% | 314 to 365 | 100% |
Below 50%, care rounds down to a whole percentage. Above 50%, it rounds up. Read the DSS care-rounding explanation.
Account for Other Children and Cases
The comparison keeps income, dependants and care unchanged.
Relevant dependent children reduce the parent’s child support income through a separate allowance. Enter their ages and the parent’s care percentage.
The dependent-child input assumes the same care percentage for every dependent child listed for that parent. Each must meet the relevant dependent child definition.
Children assessed in another child support case belong in the other-cases field. Their ages determine a multi-case allowance. A separate cap limits each child’s payment.
Add one five-year-old in Parent A’s other case to the default example. All other inputs stay unchanged. The multi-case allowance is $3,600 and Parent A’s child support income falls to $26,400.
The formula gives $3,003 before the cap. The child’s $2,736 multi-case cap reduces the annual amount to $2,736, compared with $3,468 without the other case.
For multiple cases, the tool calculates age-specific costs for each child under Formula 3. It reports only this case’s payment, not the total across every family.
Compare an Estimate With an Assessment
Periodic equivalents divide the annual amount by 52, 26 or 12 for budgeting. They are not the official collection schedule.
The estimate uses the circumstances you enter for a 2026 assessment period. It assumes those circumstances stay constant for the annual calculation.
Changes in income, a child’s thirteenth birthday or care arrangements can change the assessment during a period. Agreements and departures can also replace the formula outcome.
Minimum-rate rules and fixed-rate rules need additional eligibility facts. This calculator reports the formula amount before those rules.
Non-parent carers, adult children and different care percentages among a parent’s relevant dependants require a calculation outside this tool’s input scope.
The Australian assessment formula applies across the states. A Queensland, New South Wales, Victoria or Western Australia label does not select a different rate table.
Centrelink administers benefits separately from child support. Income support can affect which child support rules apply. Use Services Australia’s formula guidance when comparing the result with an assessment.
When the income figure is disputed, compare the client’s records using the child support income guide before changing the scenario.