Child Support Change Of Assessment : All 10 Reasons Explained

The child support formula doesn’t always get it right. It’s a mathematical calculation based on incomes and care percentages.

While it’s supposed to provide a “standard” framework for all Australians, in reality, life isa lot more complicated and messier than a spreadsheet.

That’s why the law lets either parent apply for a change of assessment.

It’s a formal request asking Services Australia to look beyond the formula and consider special circumstances.

People often call it a COA (change of assessment) or a child support departure from the standard formula.

There are 10 reasons you can use to apply.

Each covers a different set of special circumstances in child support cases.

At Unified Lawyers, we help parents through this process regularly. Below, we explain every reason, when each one applies, and what evidence you’ll need.

What Is a Change of Assessment (COA)?

A change of assessment, sometimes called a COA for child support, is an application to Services Australia asking them to adjust the child support amount because of special circumstances.

It’s set out in Part 6A of the Child Support (Assessment) Act 1989.

The application is free. You fill in the child support change of assessment form (available on the Services Australia website), explain which reason or reasons apply, and provide your evidence.

A Senior Case Officer (SCO) reviews the application, usually contacts both parents by phone, and then makes a decision.

The process typically takes between 6 to 10 weeks. Complex cases can run longer.

One thing to understand: the SCO doesn’t have to change anything.

Even if your reason is valid, they’ll only adjust the amount if it’s fair to do so.

That means fair to both parents and to the children.

The 10 Reasons

Each reason fills a specific gap in the formula. You can cite more than one in a single application.

These are the grounds for special circumstances child support claims.

Here’s what each covers and when it applies.

Reason 1 : High Costs of Caring for the Child

This applies when you’re paying for things the formula doesn’t cover.

The most common example is private school fees or medical/dental expenses.

If your child needs orthodontic treatment, speech therapy, or ongoing specialist care that Medicare or private insurance doesn’t fully cover, Reason 1 may help.

You’ll need to show the costs are necessary and that the current child support amount doesn’t cover them.

Keep all receipts and invoices. A letter from the treating professional explaining the need for treatment will make your case stronger.

Reason 2 : High Costs of Contact with the Child

If you’re spending a lot of money to maintain contact with your child, usually because the other parent has moved far away, Reason 2 may apply.

Think interstate flights, long-distance driving costs, or accommodation for contact visits.

The costs need to be large relative to your income.

A $200 flight twice a year probably won’t qualify.

But if you’re flying Melbourne to Perth every school holidays at $600 a return trip, plus hotel stays, that adds up.

The SCO may reduce your child support to offset those expenses.

Reason 3 : High Contact Costs for the Other Parent

This is the mirror of Reason 2.

If the other parent is the one spending heavily on travel to see the child (and you’re the one who moved), they can apply under Reason 3.

The same test applies: the costs have to be necessary, reasonable, and large enough to matter.

Reason 4 : Necessary Commitments to Support Yourself or Another Person

Reason 4 covers money issues that cut into your ability to pay.

This might include debts from the marriage, the cost of looking after an elderly parent, or your own medical bills.

This reason is harder to win than most people think.

The SCO will check whether the expense is truly needed or just a choice.

A mortgage on the family home?

Likely valid. A car loan for a luxury vehicle?

Almost certainly not.

Reason 5 : Necessary Commitments by the Other Parent

The flip side of Reason 4.

If the other parent has necessary financial commitments that increase their need for child support, they can apply here.

The same “necessary versus optional” test applies.

Reason 6 : High Child Care Costs

If you’re paying unusually high child care fees, and the formula doesn’t cover them, Reason 6 can help.

Full-time long day care, before- and after-school care, or specialised care for a child with extra needs are all common examples.

You’ll need evidence of the actual costs and proof that they’re necessary for work or study.

Reason 7 : Child’s Financial Resources

This one is rarely used. It applies when the child has their own income or assets, like a trust fund, an inheritance, or income from a family business.

The argument is that the child’s own resources reduce what the parents need to contribute.

Reason 8 : A Parent’s Income, Property, Financial Resources, or Earning Capacity

This is the most commonly cited change of assessment reason 8, and it generates the most disputes by far.

Reason 8 child support claims apply in two main scenarios.

First, when a parent’s real financial position is much better than their taxable income shows.

This covers parents who own major property, receive trust distributions, hold company assets, or get non-taxable benefits.

If someone lodges tax returns showing $50,000 but lives in a multimillion dollar house and drives a luxury car, that’s a textbook Reason 8 case.

Second, it applies when a parent has deliberately reduced their earning capacity.

If the paying parent quits a well-paying job to work part-time or take a lower-paid role without a legitimate reason (like illness or caring duties), the SCO can impute a higher income.

This is called income minimisation, and Services Australia takes it very seriously.

Evidence is everything with Reason 8.

Bank statements, property valuations, company financials, trust distribution records, loan documents.

Bring everything you have.

The more concrete your evidence, the stronger your case.

If you’re on the receiving end of a Reason 8 application, expect to disclose your financial position in detail.

We handle reason 8 child support cases regularly at Unified Lawyers.

The process can feel daunting, but with solid preparation and legal support, it’s very manageable.

Talk to our child support team if you think Reason 8 applies to your situation.

Reason 9 : Child Support Already Provided Through Property or Lump Sum

If a parent has already made a lump sum payment or transferred property specifically to cover future child support (for example, as part of a property settlement), Reason 9 lets the SCO factor that in.

Ongoing payments can be reduced to reflect what’s already been provided.

The key word is “specifically.”

You need clear evidence that the payment or transfer was meant to cover child support, not just part of a general asset split.

Without that documentation, this reason is hard to win.

Reason 10 : Special Needs of the Child

This covers children with disabilities, chronic illness, or other special needs that create costs beyond what the formula expects.

If your child needs specialised equipment, therapy, modified schooling, or full-time care that goes well beyond normal parenting costs, Reason 10 can be used to increase the child support amount.

Medical reports and specialist assessments are essential.

The stronger your documentation, the better the outcome.

If costs are ongoing, include a forecast of future expenses as well.

How to Apply for a Change of Assessment

The process is more straightforward than most people think.

Download the application form from the Services Australia website, fill it in, and submit it with your supporting evidence.

There’s no fee.

After you lodge, Services Australia will tell the other parent and give them a chance to respond.

A Senior Case Officer reviews everything.

They may call both parents by phone to discuss the details.

After that, they put their decision in writing.

If you disagree with the outcome, you have options.

You can object within 28 days.

If the objection fails, you can appeal to the Administrative Appeals Tribunal (AAT) or apply to the Federal Circuit and Family Court of Australia for a child support departure order.

Each path has different costs and timelines, so it’s worth getting advice before choosing.

Tips for a Stronger Application

We’ve reviewed hundreds of these applications over the years.

Here’s what separates the ones that succeed from the ones that don’t.

Lead with evidence, not emotions. The SCO is making a legal decision, not a moral one. Bank statements, payslips, medical reports, and receipts carry weight. Complaints about your ex’s behaviour usually don’t.

Be specific about the amount. “I think I should pay less” is weak. “I believe my assessment should be reduced by $3,200 per year because I spend $6,400 annually on travel to maintain contact” is strong. Give the SCO a clear number and the reasoning behind it.

Don’t overreach. Applying under five reasons when only two are genuinely relevant hurts your credibility. Pick the reasons that fit your situation and focus your energy on those.

Consider getting legal help. A solicitor can review your evidence, spot gaps, and present your case in the strongest terms. That’s not strictly required, but it makes a real difference. Especially for Reason 8 cases where financial disclosure and analysis are involved.

What If the Other Parent Applies for a Change of Assessment Against You?

Don’t ignore it.

If you don’t respond, the SCO will make a decision based on whatever information they have, and that’s unlikely to go in your favour.

When you receive notice of a COA application, you have a set period to respond.

Use that time.

Gather your financial documents, prepare a written response that addresses each of the other parent’s claims, and consider whether legal advice would help.

If the application involves Reason 8 and questions about your income or assets, you’ll likely be asked to provide detailed financial disclosure.

Cooperating fully and being transparent actually works in your favour.

Trying to hide things almost always backfires.

Change of Assessment vs Court Departure : What’s the Difference?

People often confuse these two options. A change of assessment is handled by Services Australia.

You fill in a form, provide evidence, and a case officer makes a decision. It’s free and you don’t need a lawyer (though having one helps).

A court departure is handled by the Federal Circuit and Family Court.

It’s a formal legal process with filing fees, court dates, and (usually) lawyers on both sides.

The court has broader powers than a case officer.

A judge can consider a wider range of factors and make orders that go beyond what the COA process allows.

Most parents start with a COA.

If that doesn’t produce a fair result, the court is the next step.

Some parents go straight to court if the amounts involved are large or the circumstances are highly contested.

Your choice depends on the complexity of your case and how much is at stake.

For a relatively simple Reason 1 or Reason 2 claim, the COA process is usually enough.

For a contested Reason 8 case involving hidden assets or corporate structures, the court may be the better path.

Common Mistakes People Make with COA Applications

We see these errors come up time and again.

Waiting too long to apply is problematic.

If your circumstances have already changed, every month that you wait is money you could be getting back or saving.

Applications can be backdated in some cases, but it’s harder to argue for that than to apply promptly.

Not including enough evidence hurts your case.

Saying “my ex earns more than they declare” without proof gets you nowhere.

Bank statements, property records, and company searches carry weight.

Vague claims don’t.

Mixing up the COA process with a complaint is a waste of time and effort.

A change of assessment is not the place to air grievances about the other parent’s behaviour.

Stick to the financial facts.

Forgetting that the other parent can respond.

Whatever you put in your application, the other side will see it and get a chance to respond.

Don’t say anything you can’t back up.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.