Child support assessment

How we assess the amount of child support you need to pay or receive. The formula we use to work it out is in Australian law.

You need to know

The assessment formula

The child support assessment formula looks at your circumstances to work out how child support should be paid.

How we work out who pays

Normally you’ll:

  • pay child support if your percentage of care of a child is less than your share of the combined income, or
  • receive child support if your percentage of care of a child is more than your share of the combined income

How we work out the amount

We look at:

  • the parents’ income and combined income
  • how much time each parent cares for the child, and
  • the child’s age

The costs of a child we work out is based on research into what parents spend on children in Australia.

The figures change each year to keep up with current costs and incomes.

Read more about our basic formula for child support amounts on the Child Support Guide website.

Read details of child support amounts on the Department of Social Services website.

Link between child support and Family Tax Benefit

You may need to apply for a child support assessment to receive more than the base rate of Family Tax Benefit Part A.


  • the more child support you receive, the less Family Tax Benefit you receive, and
  • the less child support you receive, the more Family Tax Benefit you receive


To be eligible for a child support assessment you must:

  • meet the residency rules, and
  • be a legal parent or non-parent carer of the child

Legal parents

You and the other parent in your application must both satisfy us that you are the child’s legal parents.

You’ll satisfy us if at least one of the following applies:

  • the parents were married when the child was born
  • the child’s birth certificate names you as parent, it can be Australian or from a reciprocating jurisdiction
  • adoption papers name you as a parent
  • the person is male and lived with the mother any time between 20 to 44 weeks before the child’s birth
  • you have a statutory declaration:
    • that states you’re the child’s parent
    • that the other parent is named on the birth certificate, or
    • by a non-parent carer that one or both parents are named on the child’s birth certificate
  • a clear statement from a relevant court that a person is the child’s parent, or
  • you are a parent under the Family Law Act 1975 - this covers artificial conception and surrogacy

We’ll investigate if there’s conflicting evidence about who’s the parent.

Non-parent carers

You may be able to do one or both of the following:

  • apply for a child support assessment
  • make a child support agreement

Read about assessments for non-parent carers below.

How your percentage of care affects your child support payments

Our child support assessment considers each parent or non-parent carer’s care of the child. This is their percentage of care.

Read more about how your care arrangements affects your child support

How your income affects your payment

We consider each parent’s income equally when we make a child support assessment. We don’t use income from non-parent carers.

Read more about income considered when calculating child support

Basic formula

This formula is for parents with only 1 child support assessment.

Read more about working out payments using the basic formula

Child support period

A child support period is the amount of time an assessment covers. It can be up to 15 months.

When a new child support period starts

A child support period will start:

  • on the day you make an application for child support
  • on the day you make an application to accept a child support agreement, if it starts a new case
  • on the day a child support agreement changes a child support assessment,
  • the day after the current child period ends, or
  • when the ATO tells us new income information for the most recent financial year, if that year of income isn’t already used in an assessment

If a new ATO income starts a child support period, it starts:

  • on the 1st day of the next month if we receive the ATO income by the 15th of the month, or
  • on the 1st day of the month after next if we receive the ATO income after the 15th of the month

Changes during a child support period

We can update your assessment at any time. You must tell us as soon as you can if your circumstances change. For example, we need to know if:

  • your income changes, or
  • the amount of time the child lives with you changes

Your child is turning 18 and is still at school

Normally child support stops when the child turns 18.

You can apply to extend it to the end of the school year if your child will be in full time secondary education when they turn 18.

If you have a child support agreement, you may be able to extend it. Contact us to find out.

You can also apply to have a relevant dependent child included in your assessment after they turn 18. They’ll need to be in full time secondary education.

When to apply

You need to apply while the child’s 17. We’ll remind you to do this before they turn 18.

We can only accept an application after a child turns 18 in limited circumstances.

Family Tax Benefit

If you don’t extend your child support after your child turns 18, you can only receive the Family Tax Benefit Part A base rate.

How to apply

You can apply by:

Child support for same-sex parents

You and the other person on your application must be the child’s parents or a non-parent carer.

Read about who can apply for an assessment.


You’re a parent if you have adopted the child.

Artificial conception

Parents must have been in a de facto relationship at the time of the artificial conception procedure and both agreed to the procedure.

Case study

Nicole and Samantha are in a de facto relationship. They decide to have a child together and agree Nicole will be the birth mother. She conceives their daughter Louisa using donor sperm.

They break up. Nicole has full time care of Louisa. She applies for a child support assessment.

We decide Samantha has to pay child support as the other legal parent.


You’re both the child’s parents if an Australian court order says you are.

If an assessment names you as your child’s non parent carer

You can ask us to change your assessment to show that you are a parent of your child. This may change the amount of child support you pay or receive.

Tell us about changes

Tell us right away about any changes that may affect child support.

You can do this by:

Assessments for non-parent carers

If you care for a child and you’re not their parent, you may be able to receive child support from one or both parents.

If you’re a non-parent carer, our Grandparent Advisers are there to help you. They support grandparents, other family members, legal guardians and others who care for someone else’s children.

Read about Grandparent Advisers.

Who can apply

You can apply for non-parent carer child support if all of these things are true:

  • you care for the child for at least 128 nights a year
  • you aren’t the partner of either of the child’s parents
  • you don’t have joint care with either of the child’s parents
  • the people you’re asking for child support from are:
  • the child’s parents have agreed to you caring for the child - they don’t need to agree to this if it would be unreasonable for them to care for the child

How to apply

You can contact us or can fill in an Application for child support assessment - Non-parent carer.

You must apply for child support from both parents unless:

  • one parent doesn’t live in Australia or a reciprocating jurisdiction
  • one parent has died, or
  • we’re satisfied there are special reasons you can’t, such as not knowing who the other parent is

How much you can receive

We base your child support assessment on:

  • the parents’ incomes
  • who cares for the child

We don’t consider your income.

Read about how percentage of care affects child support payments.

Parents with 2 or more assessments

We work out how much child support you pay or receive if you have 2 or more families from past relationships.

Your child support income is:

We then use this amount as part of the formula to calculate your child support assessment.

Multi case allowance

We work this out based on:

  • each child’s age, and
  • how much it would cost if all your children lived with you

Multi case cap

This is a limit on the amount of child support a paying parent can pay. We cap the amount of child support a parent pays so it won’t cost more than if all your children live with you.

We work out the multi case cap and child support assessment for each child. If your assessment is higher than the multi case cap, you won’t pay more than the multi case cap.

Child support parents with second families

If you have children from a new family, we reflect this in your assessment.

Read more assessments with second families

Fixed and minimum assessments

We can base some child support assessments on a fixed rate or a minimum rate.

Read more about minimum and fixed assessments

Residence rules

We can make a child support assessment if:

  • both parents are residents of Australia
  • one parent is a resident of Australia and the other parent is a resident of a reciprocating jurisdiction, or
  • the paying parent is a resident of Australia and the child is either present in Australia, ordinarily resides in Australia or they’re an Australian citizen

Parents who live in a reciprocating jurisdiction can apply for a child support assessment. You need to submit your application with the overseas authority in your country of residence. That country must then send the application to us.

Parents who can’t apply for a child support assessment may be able to apply for a court order for child maintenance. This can be completed through your state or territory court dealing with family matters.

Read more about child support when parents or children live overseas.

Parenting plans

A parenting plan is a written agreement with the other parent. It sets rules for things like how much time the children will spend with each parent.

Read more about parenting plans

What ends an assessment

There are a few reasons why a child support assessment will end.

Read more about events that end your child support assessment


Once you have read about eligibility the next steps are:

  1. Apply for a child support assessment
  2. We'll assess your application and let you know the outcome



Choose a collection option

The person who will receive child support can choose how the paying parent pays them.

Read more about collection options

Private Collect

This is where you and the other parent make and receive payments directly between you. It’s for parents who don’t need much help from us to agree on a plan.

Read more about Private Collect payments

Child Support Collect

This is where we collect and transfer child support payments for you.

Read more about Child Support Collect payments

Self employed parents

If you’re self employed and pay child support through us, you can use most payment methods.

Overdue payments

If you have overdue payments we try to agree with you on a plan to pay back the debt.

If we can’t make a plan we can send a garnishee notice. This requires someone to pay money to us instead of paying it to you.

For example, it could be a business you work for on contract. We can tell them to do this for a one off amount, a regular payment, or a number of cents per dollar.

What counts as income

When you’re self employed you can legally reduce your taxable income by claiming some expenses as tax deductions.

This may mean you have more financial resources than your taxable income shows.

Read about income we use to work out child support.

Changing your assessment

We can change your child support in special circumstances if you have more financial resources than your taxable income shows.

Either parent can also apply. Read about changing your child support assessment in special circumstances.

Changes of circumstances that affect your child support

We need to know about changes that could affect your child support.

Read more about how a change of circumstances can affect your child support

Changing your child support assessment in special circumstances

We can change your child support if we’re satisfied there are special circumstances and the change would be fair to both parents and the child.

Read more about changing your assessment in special circumstances

Applying for a change of assessment

Fill in the Application to change your assessment – special circumstances form.

Send it to us online or by post. Details are on the form.

Child support and military deployment

When you leave Australia on military deployment you need to tell us your new details. This is so we can make sure your child support is still accurate.

Read more about responsibilities when you are being deployed

Child support if you go to prison

You must tell us if you go to prison. This is so we can make sure your child support is accurate.

What happens if you don’t tell us

We’ll keep basing your child support on your income and care percentage from before you went to prison. This means you may:

  • pay too much child support
  • build up a debt, or
  • receive too much child support and have to pay it back

When to tell us

Tell us as soon as you can. Normally we can only change your payments from the date you tell us about the change. We can’t backdate the new amount.

What to tell us

Tell us:

  • your address in prison
  • the best way to contact you while you’re in prison
  • your income while you’re in prison - you need give details of any:
    • income or allowances you earn in prison
    • money from investments or other income you receive outside prison, and
  • if the care arrangements for your children will change while you’re in prison - if you normally have care of your child, your payments may change

Getting someone else to deal with us for you

You can choose someone to deal with us for you while you’re in prison. This can be a person or an organisation. If you want them to, they can:

  • ask us about your child support, and
  • give us information about you

They can’t:

Read about getting someone to deal with us on your behalf.

How to do this

Use the Representative authority form.

Telling the other parent

We won’t tell the other parent you’re in prison. We must tell them if we reduce or stop any child support you pay. We won’t tell them why.

While living outside Australia

In some cases we can help separated parents with child support arrangements for their children when one parent lives in another country.

Read more information about child support when parents and children live overseas.


Child support care percentage estimator

The care estimator is a tool that calculates your care percentage.

We use this figure when we decide:

  • who pays child support
  • how much you pay or receive

Read about the assessment formula.

How it works

Open the care estimator then:

  • enter the Care period start date - this starts on the day the care changed and usually ends 12 months later
  • choose:
    • select recurring care – the nights the child lived with you every week, or
    • manually select care dates – single nights the child lived with you
  • in the Total care estimate box, select Calculate
  • the box will show your:
    • total nights of care
    • care percentage
    • care level

Fact sheets in your language

We have fact sheets on child support in many other languages.


You can choose to read about:

  • paying child support when the other parent lives outside Australia - amount set overseas
  • paying child support when the other parent lives outside Australia - amount set in Australia
  • paying child support when you live outside Australia
  • receiving child support when you live outside Australia
  • receiving child support when the other parent lives outside Australia
  • paying child support when you live in New Zealand
  • receiving child support when the other parent lives in New Zealand

Where to find them

Go to information in your language:

  • choose from the list of languages
  • choose from the Read list

Payment and Service Finder

Find, estimate and compare payments and services you may be eligible for. You can also work out what a change in circumstance might mean for the payments and services you currently receive from us.

Start using Payment and Service Finder

Manage your money


We’ve got advice and tools to help you with budgeting, borrowing and credit, and managing debt.

Read about how to manage your money.

Regular deductions using Centrepay

You can use our free and voluntary service to pay bills as regular deductions from your Centrelink payments.

Read more about regular deductions using Centrepay

Page last updated: 11 September 2017