Child Support: A Practical Guide

The formula, in plain language

Child support in Australia is administered by Services Australia rather than the family court, and it runs on its own rules. If you are separating now, it sits alongside your parenting arrangements but travels on a completely separate track.

The assessment works through a fixed sequence. Each parent’s adjusted taxable income is established. A self-support amount, $31,046 for child support periods starting in 2026, is set aside for each parent first, because you are allowed to keep yourself alive before supporting anyone else. What remains is combined, and a costs table converts that combined income into a dollar cost for your children based on their number and ages. Each parent then wears a share of that cost equal to their income percentage minus their care-based cost percentage.

Care is counted in nights per year. Below 52 nights a year (under 14% of care) a parent’s care does not reduce their liability. From 52 nights, recognised as regular care, it starts to offset the bill, and the offset grows as care approaches equal time.

The formula itself is mechanical, so there is very little point arguing with it. What you can do is challenge what goes into it. Almost every child support dispute we see comes down to a single input: the other parent’s true income, the real care percentage, or a cost the table was never built to cover.

When the formula gets it wrong

The assessment assumes the tax return tells the truth. Where a parent is self-employed, paid partly in cash, or drawing a deliberately small wage from their own company or trust, the taxable income going into the formula can be a fraction of the real position. The law allows a departure from the assessment in defined circumstances: where income or earning capacity is not reflected in taxable income, where the costs of seeing the children are high because of distance, where a child has special medical or education needs, or where private school fees were part of how the children were being raised.

A departure application goes to Services Australia first, and objections to decisions can then be reviewed by the Administrative Review Tribunal. Neither step is quick, and both run on evidence. Bank records, business accounts and lifestyle evidence are what decide these applications, so knowing what to gather before you lodge makes a real difference to the result.

Doing your own deal instead

Parents who want certainty can contract out of the formula. A limited agreement fixes an amount at or above the assessment. A binding child support agreement can set any figure and fold in school fees, health cover and extracurricular costs, but it requires independent legal advice on both sides and is built to be hard to escape, even if your income later collapses. We advise on and draft both, and we tell you honestly when the formula would serve you better than a signed agreement.

Where to get help with the wider picture

Child support rarely travels alone. The same separation usually involves dividing the assets, covered in our divorce settlement guide, and formalising arrangements for the children. Our family lawyers look at the three together, because a decision in one, such as who keeps the house, shifts the numbers in the others.

If your assessment looks wrong, a departure or objection deadline is approaching, or you have been handed a binding agreement to sign, call 1800 130 120. The first conversation is free, and it will tell you whether the number you are staring at is worth fighting.