How Child Support Is Calculated in Australia (2026)
This guide explains how the standard formula works. For your specific circumstances, speak with a family lawyer or contact Services Australia directly.
The 8-Step Formula
Services Australia applies the same formula to every assessment in Australia. Understanding each step shows exactly where your number comes from.
Work out each parent's child support income
A parent's child support income is their adjusted taxable income (ATI), minus the self-support amount, minus any relevant dependent child amount, minus any multi-case allowance.
What is ATI?
ATI is not the same as take-home pay or simple taxable income. A parent's ATI is the total of:
- taxable income
- reportable fringe benefits total
- target foreign income
- total net investment loss
- total of any tax-free pensions or benefits
- reportable superannuation contributions
Net investment losses (for example, rental property losses that exceed rental income) are added back to taxable income. This prevents a parent from reducing their assessed income by offsetting investment losses against other earnings.
What is not included in ATI?
A new partner's income is not included. Child support is assessed only on the parents' incomes. NDIS amounts, National Redress Scheme payments, and Territories Stolen Generations Redress Scheme payments are also excluded.
What if a parent is self-employed?
The ATI used is what each parent reports to the ATO. Where a parent has structured their financial affairs — through a business, trust, or company arrangement — in a way that reduces their reported income, either parent can apply for a Change of Assessment. Under Reason 8A, the Registrar can look beyond ATI to consider a parent's broader financial position, including retained profits and business resources.
The self-support amount
Each parent keeps a baseline before the formula applies. The self-support amount in 2026 is $31,046[2] — representing the minimum income a parent is assumed to need for their own support. This is deducted from ATI as part of the Step 1 calculation.
If a parent's ATI is less than $31,046, their child support income is treated as zero. Parents with zero assessable child support income are generally still required to pay the minimum annual rate (MAR) of $534[2] per year (indexed to CPI each January).
Work out the combined child support income (CCSI)
Both parents' child support incomes are added together to give the combined child support income. This figure is used later in Step 7 to look up the costs of the children.
Example: Parent A ($53,954) + Parent B ($23,954) = CCSI $77,908.
Work out each parent's income percentage
Each parent's individual child support income is divided by the CCSI to give their proportional share of financial responsibility for the children.
Example: Parent A: $53,954 ÷ $77,908 = 69.3% | Parent B: 30.7%.
Work out each parent's percentage of care
The percentage of care is the proportion of nights per year each parent has with the children, divided by 365. A different percentage of care may apply for each child if care arrangements differ between children.
Work out each parent's cost percentage
The percentage of care is converted to a cost percentage using a legislated table (CSA Act s.55C). The cost percentage represents how much of the children's direct costs that parent's care time is taken to cover.
| Nights per year | Care percentage | Cost percentage |
|---|---|---|
| 0–51 | 0–13% | 0% |
| 52–127 | 14–34% | 24% |
| 128–175 | 35–47% | 25% + 2% per 1% over 35% |
| 176–189 | 48–52% | 50% |
| 190–237 | 53–65% | 51% + 2% per 1% over 53% |
| 238–312 | 66–86% | 76% |
| 313–365 | 87–100% | 100% |
A parent with zero overnight care has a cost percentage of 0% and receives no credit for direct costs. A parent at exactly 50/50 care has a cost percentage of 50%.
Work out each parent's child support percentage
Each parent's child support percentage is their income percentage (Step 3) minus their cost percentage (Step 5).
- A positive result means that parent pays child support
- A negative result means they receive it. If a fixed rate applies, that rate overrides the formula result instead.
Work out the costs of the children (COTC)
Services Australia uses legislated expenditure tables to estimate what two parents at the combined income level would typically spend raising their children. The figure varies by:
- combined child support income (five income bands, updated annually)
- number of children
- age of the children
The COTC tables are updated each year on 1 January. They are a standardised benchmark, not an accounting of each family's actual expenses. The table applies only up to a combined child support income of $232,843[2] — above this, the COTC figure does not increase further.
Calculate the annual rate payable
If a parent has a positive child support percentage from Step 6, their annual rate of child support is:
Run your own numbers in less than a minute — enter both parents' incomes, care nights, and number of children.
Use the Free CalculatorHow Care Percentage Affects the Result
Care percentage feeds directly into the formula in Step 5, converting to a cost percentage that represents how much of the children's direct costs that parent is assumed to cover through their time with the children. That cost percentage then flows into Step 6, where it's subtracted from the income percentage to determine who pays and how much.
At exactly 50/50 care, both parents have a cost percentage of 50%. Whether a payment applies depends on whether each parent's income percentage also sits at 50%. If one parent earns significantly more, their income percentage will exceed their cost percentage and a payment will apply, even with equal care nights.
For a detailed breakdown of how shared care scenarios work, see 50/50 care and child support.
Worked Example — 2026 Figures
Two parents, one child aged 9. Parent A earns $90,000 ATI, has 4 nights per fortnight (104 nights/year, 28% care). Parent B earns $52,000 ATI, has 10 nights per fortnight (261 nights/year, 72% care).
| Step | Parent A | Parent B |
|---|---|---|
| ATI | $90,000 | $52,000 |
| Less self-support | ($31,046) | ($31,046) |
| Child support income | $58,954 | $20,954 |
| CCSI: $79,908 | ||
| Income percentage | 74.0% | 26.0% |
| Care percentage | 28% | 72% |
| Cost percentage | 24% | 76% |
| Child support percentage | 50.0% (74% − 24%) | −50.0% (26% − 76%) |
At a CCSI of $79,908, the 2026 Costs of Children table for one child aged 9 is $12,917.85.[1]
Parent B's result is negative. Their direct care already covers more than their income share, so they receive the payment rather than making one.
Scenario 2 — 50/50 care, unequal incomes
Two different parents, one child aged 9. Parent A earns $100,000 ATI with 183 nights (50% care). Parent B earns $42,000 ATI with 182 nights (50% care). This is the most common misconception: that equal care means no payment.
| Step | Parent A | Parent B |
|---|---|---|
| ATI | $100,000 | $42,000 |
| Less self-support | ($31,046) | ($31,046) |
| Child support income | $68,954 | $10,954 |
| CCSI: $79,908 | ||
| Income percentage | 86.3% | 13.7% |
| Care percentage | 50% | 50% |
| Cost percentage | 50% | 50% |
| Child support percentage | 36.3% (86.3% − 50%) | −36.3% (13.7% − 50%) |
At a CCSI of $79,908, the 2026 Costs of Children table for one child aged 9 is $12,917.85.[1]
Equal care doesn't produce a zero result. Parent A's 86.3% income share is well above their 50% cost share, so they pay the difference regardless of the equal care split.
What Can Change the Formula Result
The standard formula doesn't capture every circumstance. Several things can alter the assessed amount:
Other dependent children
If either parent supports other children (biological, adopted, or step-children where a court maintenance order requires it) they have a legal obligation to maintain, a relevant dependent child amount is deducted from their ATI before the formula runs, reducing their effective child support income.
Multi-case allowance
Where a parent has child support assessments for children from more than one relationship, the formula accounts for both obligations, preventing one set of children from being disadvantaged.
Change of Assessment
Either parent can apply if the formula assessment does not reflect the special circumstances of their case. For example, this covers situations where the formula result doesn't account for unusually high costs of spending time with the child, a parent's income not reflecting their true earning capacity, or significant assets and financial resources. This includes where a parent believes the other is not working, working reduced hours, or has changed occupation. Under Reason 8B, the Registrar can assess a parent against their earning capacity rather than actual income, though this does not apply where the parent's decision is justified by caring responsibilities or state of health. See the Change of Assessment guide for full details.
Binding child support agreements
Parents can agree to a different amount in a binding agreement, which overrides the formula. Each party must receive independent legal advice before entering into the agreement.
How Services Australia Gets Your Income
Services Australia receives income information directly from the ATO, based on the most recent tax year. This creates a lag: if your income has changed significantly this financial year, your assessment will continue to reflect last year's figures until you lodge your next tax return.
If your income has dropped by 15% or more, you can lodge a current year income estimate with Services Australia.
Private Collect vs Agency Collect
Once an assessment is made, payments don't have to flow through Services Australia. Many parents opt for private collect, making payments directly between themselves based on the assessed amount without Services Australia acting as intermediary.
Agency collect is where Services Australia is responsible for collecting and transferring the amount payable. This adds an enforcement layer if payments fall behind.
Either approach uses the same assessed amount. The difference is who handles the mechanics and who steps in if things go wrong.
Frequently Asked Questions
How is child support calculated in Australia?
Child support is calculated using an 8-step Services Australia formula. It takes both parents' adjusted taxable incomes, deducts a self-support amount ($31,046 in 2026), determines each parent's share of the combined income, looks up the legislated cost of raising the children at that income level, then adjusts for how much time each parent spends with the children. The paying parent covers the gap between what the formula says they owe and what their direct care already contributes.
What income is used to calculate child support?
Services Australia uses adjusted taxable income (ATI): broadly taxable income plus reportable fringe benefits, reportable superannuation contributions, target foreign income, and net investment losses. The ATO provides this directly to Services Australia based on the most recent tax year. A new partner's income is not included.
Does 50/50 care mean no child support?
Not automatically. Equal care sets both parents' cost percentages to 50%, but if one parent earns significantly more, their income percentage will exceed their cost percentage and a payment will still apply. The income split, not just the care split, is what determines the result.
What is the self-support amount for 2026?
The self-support amount is $31,046 for the 2026 assessment year. It is deducted from each parent's ATI before calculating their child support income, and is updated annually.
Can child support be changed after it's assessed?
Yes. Either parent can apply for a Change of Assessment if the formula assessment does not reflect the special circumstances of their case. For example, this covers situations where it does not account for unusually high costs of spending time with the child, a parent's income not reflecting their true earning capacity, or significant assets and financial resources. Income is also updated when a parent lodges a new tax return with the ATO, or when more accurate income information becomes available that overrides what was previously used.
Is child support taxable income?
No. Child support payments are not assessable income for the receiving parent and are not tax deductible for the paying parent under Australian tax law.
What is the minimum child support payment in Australia?
Where a parent has below regular care (less than 14% of nights, under 52 nights per year), a minimum annual rate applies even if their assessed child support income is zero. The minimum annual rate (MAR) is $534 per year (indexed annually to CPI). It applies unless they qualify for a suspended assessment.
Run Your Own Numbers
Less than a minute — enter both parents' incomes, care nights, and number of children to get a 2026 estimate.
Use the Free CalculatorIf your situation involves disputed incomes, a Change of Assessment application, other dependent children, or a binding agreement you want formalised, a family law specialist can help.
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