Income percentage
Income percentage in the Australian child support formula is each parent’s share of the combined child support income. Child support income is each parent’s income minus the self-support amount, and income percentage is calculated by dividing each parent’s amount by the combined total.
Income percentage reflects relative income, not actual spending. It is compared with each parent’s cost percentage (based on care) to determine the final payment outcome.
Key takeaways for parents
The use of income percentage is a reminder that child support is based on the incomes of the parents. Whoever earns a greater share of the income pool is expected to contribute more financially.
- A parent with the higher income percentage is expected to meet more of the child’s costs through payments or direct spending; and
- Each parent’s expected financial contribution is adjusted for the costs they meet through their level of care.
A parent with no child support income has a zero income percentage and will generally rely on the other parent financially. Prescribed minimum contributions may still apply when they have less than shared care.
Income percentage definition
Income percentage is worked out by dividing a parent’s child support income by the combined child support income of both parents and expressing the result as a percentage.
Definition source: Guides to Social Policy Law, Child Support Guide, Income percentage.
Meaning in the child support formula
Income percentage is each parent’s share of the combined child support income. To calculate the percentage, you first subtract the 2026 self-support amount of $31,046 from each parent’s ATI. ATI stands for adjusted taxable income, which for most parents is simply their taxable income.
You then divide each parent’s child support income by the combined total.
A parent with the larger share of the combined child support income has the larger income percentage. The resulting percentage represents each parent’s share of financial responsibility in the formula.
Income percentage calculation
Income percentage is calculated by comparing each parent’s child support income to the combined total. Child support income is each parent’s ATI (adjusted taxable income) minus the self-support amount.
Take Ken and Barbie. Ken’s taxable income is $150,000 and Barbie’s taxable income is $100,000. After subtracting the 2026 self-support amount of $31,046, their child support incomes are $118,954 and $68,954. Their combined child support income is $187,908.
The calculated percentages show each parent’s share of the combined child support income. Each percentage represents the parent’s share of financial responsibility before their care contribution is taken into account.
Effect on child support payments
Income percentage is compared with each parent’s cost percentage, which reflects how much of the child’s costs they meet through care.
- A positive percentage means the parent pays child support
- A negative percentage means the parent receives child support
Continuing the example, Ken’s income percentage is 63.3%. If his cost percentage is 24%, his child support percentage is 39.3%.
If the total annual cost of the children is $20,000, Ken pays 39.3% of that amount, which is $7,860 per year.
Effect of income estimates
Income percentage is based on the income used in the assessment. If a parent’s income drops by 15% or more, they can elect to use an income estimate instead of the previous financial year.
The estimated income replaces the earlier income figure in the calculation. Replacing the earlier figure can change the combined child support income and shift each parent’s income percentage. Services Australia later checks the estimate against actual income and adjusts the assessment if needed.