How Services Australia calculates support based on both parents' incomes, care percentages, and the ages of your children.
Arranging child support directly between parents, and documenting it so it holds up if a dispute arises later.
Formal agreements lodged with Services Australia that lock in terms beyond what the standard formula would produce.
Applying to vary an assessment when income, care, or your children's needs have genuinely changed.
Recovering unpaid child support, or defending yourself against an incorrect overpayment claim.
Special circumstances applications where the standard calculation doesn't reflect the real cost of raising your children.
The percentage of nights each parent has directly changes the formula. Here’s roughly where the thresholds sit.
Below 14% care – Treated as having minimal or no care, with support calculated accordingly.
14% to 34% care – Classed as regular care, which begins to offset the paying parent’s liability.
35% to 47% care – Shared care territory, where both incomes are weighed more evenly against the cost of the children.
48% to 52% care – Genuinely equal care, which can substantially reduce or even eliminate a support liability depending on the income gap.
Above 53% care – The other parent may become the one paying support, even if that feels counterintuitive given who has the children most.
As a child custody lawyer in Sydney working alongside financial assessments, we often see parents underestimate how sharp these thresholds are. A handful of extra nights a year can shift you into a different bracket entirely.
Plenty of separated parents manage child support between themselves, with no formal paperwork at all. It works well while both of you are reasonable and circumstances stay stable. The trouble starts when one of those things changes.
We see this most often after a new job, a new relationship, or a house move. Income shifts, care arrangements informally drift, and what felt fair a year ago suddenly doesn’t. Without a documented agreement, there’s nothing to point back to, and nothing enforceable if payments simply stop.
A binding child support agreement doesn’t need to feel adversarial. For many of our clients, it’s simply putting a private understanding into a form that Services Australia recognises, so neither of you has to renegotiate from scratch every time something changes.
Each parent's taxable income is assessed, with a self-support amount deducted for basic living costs.
Combined parental income determines the cost of raising your children, based on their ages and the Costs of Children Table.
Each parent's share is worked out using their percentage of combined income and their percentage of care.
The paying parent's liability is set, collected either through Services Australia or arranged privately.
A change of assessment application isn’t won by simply asserting that your ex earns more than they’ve declared or that costs have gone up. Services Australia expects evidence, and vague applications are routinely rejected.
Strong applications lean on specifics: bank statements showing undeclared cash income, receipts for a child’s medical or educational costs the standard formula doesn’t cover, or documentation showing a genuine and lasting change in care nights. General frustration about fairness, without paperwork behind it, rarely shifts an outcome.
As a lawyer for child support disputes, we help clients gather exactly the right evidence before lodging, rather than filing a weak application and having to start again after a rejection.
You can apply for a change of assessment or a departure from the formula. We advise on what evidence you'll realistically need to support that application.
