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Child Support Calculator

The child support assessment formula

If you wish to understand the process for calculating child support, try working through the following steps. This basic child support assessment formula applies to parents with one child and no other dependent children.

The assessment is calculated like this:

  • 1. Work out your child support income

    This is your taxable income less the ‘parenting self-support amount’ indexed annually. The ‘parenting self-support amount’ for 2011 is $20,594.

  • 2. Work out the combined child support income

    This is both parents’ child support income amounts added together.

  • 3. Work out your income percentage

    This is the amount you got from Question 1, as a percentage of the amount you got from Question 2.

  • 4. Work out your care percentage

    This is based on the number of nights in a year that the child lives with each parent, expressed as a percentage of the year.

  • 5. Work out your cost percentage

    This is calculated from your answer to Question 4. You take the care percentage and check which category it fits into (these are set out on the CSA’s website and range from 0 per cent to <14 per cent up to >86 per cent to 100 per cent).

  • 6. Work out your child support percentage

    This is each parent’s income percentage (see Question 3) minus their cost percentage (Question 5).

    If the percentage is positive, you need to pay child support. If the percentage is negative, you are entitled to receive child support.

  • 7. Work out the cost of your child

    This is calculated using a table on the CSA website that is updated every year. It takes into account your combined child support income and then takes the cost of each child as a percentage of that number.

  • 8. Work out the child support amount

    Multiply the liable parent’s child support percentage (Question 6) by the cost of the child (Question 7). This gives the amount the liable parent will have to pay per year.