How your income affects your child support

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

Once we work out each parent’s income, we’ll know their share of the children’s costs. Your percentage of care can also affect these costs. Read about the assessment formula we use.

What income information we use

We can usually use information about your income from the Australian Taxation Office (ATO).

The income we base your payments on is your adjusted taxable income for the last relevant year. This means the financial year that ended before your current child support period.

If you live overseas, financial year means the financial year of the country you live in. Read about child support when parents and children live overseas.

To make sure we base your child support on the right income, you should always lodge your tax return on time.

What income we use if you haven’t lodged your tax return

You can tell us your adjusted taxable income for the last relevant year. If you don’t, we’ll work out a provisional income for you. This will be what we think your adjusted taxable income is likely to have been.

We may ask you for a copy of some recent pay slips to help us.

If we don’t have enough information or you don’t lodge a tax return we’ll use either:

  • your tax return for the year before and adjust it for inflation
  • two thirds of the male total average weekly earnings as your income.

We’ll use the higher of these amounts.

We may make a new assessment when you or the other parent lodges a tax return for the year.

If you live overseas, we won’t know when you lodge a tax return in the country where you live. If you have a child support assessment from us, you need to tell us your last financial year’s income. You must do this at the start of each child support period. You may need to give us proof of your income.

You need to lodge your tax return for that year as soon as possible. Read about child support when parents and children live overseas.

If you need to tell us your income

If you have all your income information, but aren’t ready to lodge a tax return, tell us your income either by:

Or, you can complete the income declaration form and submit it either by:

What if there are changes to your income

You must tell us about any changes to your income when they happen. We may be able to change your child support assessment. This includes if you stop or start getting an income support payment from Centrelink. We can’t backdate some income changes, so tell us as soon as possible.

Your current income may be lower than the income we are using in your child support assessment. If this applies to you, you may be able to tell us an estimate of your current income.

We can only accept an estimate in certain circumstances. Your current adjusted taxable income must be at least 15% lower than what we’re using in your child support assessment.

One of the following must also apply:

  • the ATO has assessed your income for the financial year we are using for your assessment
  • the ATO hasn't assessed your income for the financial year used in your assessment, but you've declared your income.

Only you can make an estimate. If you choose to make an estimate, it’s important you do it as soon as you can. We can only use your estimate from the day you tell us.

You may not be able to make an estimate if your child support involves any of the following:

When you need to update your estimate

Your income changes

If your income goes up or down you must make a new estimate of income. If your income goes down, we can’t backdate your estimate. Do this as soon as possible.

Your estimate ends before your child support period

Your income estimate lasts until the end of the financial year. Your child support period may continue into the new financial year.

If this happens you should give us a new income estimate. Do this before the end of the current financial year.

If you don’t submit a new estimate we’ll base your assessment on the income from the last financial year.

How to make an estimate

You can make an estimate in one of the following ways:

Or you can complete the Estimate of income for use in Child Support Assessment form and submit it either:

Make your estimate as accurate as you can.

What happens if you don't update your estimate

After the financial year ends we compare your estimate to your actual income for the year.

If the estimate is lower you may have to do one of these:

  • pay off a debt
  • pay back an overpayment.

What happens if you lodge your tax return late

When you haven’t lodged a tax return on time, we’ll work out your provisional income. If your actual income was lower than your provisional income, we can’t usually go back and change your child support.

Change of assessment

If you have special circumstances, you may be able to apply for a change of assessment.

Special circumstances can include any of these:

  • either parent’s financial resources, income and property aren’t being reflected in the assessment
  • either parent’s earning capacity is greater than what’s reflected in the assessment.

This can include income and financial resources that are not part of the adjusted taxable income in the child support formula.

What if you earn extra income after you separate

If you earn extra income after you separate, you may be able to exclude it from your child support assessment. For example, you might be able to exclude some of the income you earn if you start a second job.

To exclude extra income, you need to show you earned it in a pattern that started after separating. This could be from any of these:

  • getting a new job on a higher salary
  • opening your business for longer hours
  • getting a second job.

You also need to show you wouldn’t have earned it in the normal course of events. For example, it can’t be from any of these:

  • a regular pay increase
  • your usual pattern of overtime
  • ordinary seasonal changes in income.

You can only exclude income if all of the following apply:

  • you lived together with, and were in a relationship with, the other parent for at least 6 months
  • you apply to exclude the extra income less than 3 years after separating
  • you’re still separated at the time you apply.

You may be able to exclude up to 30% of your adjusted taxable income.

Both parents can apply to do this.

To apply to exclude income, complete the Application for Post Separation Income to be Excluded form.

You can then upload it using either your:

You can also send it by post or fax.

If you’re a non-parent carer, you won't need to tell us about income changes.

Call the Child Support Enquiry Line if you have any questions.

Page last updated: 11 November 2022.