Follow the 2026 eight-step income-shares method

Services Australia describes eight steps. First, each parent’s child support income is adjusted taxable income minus the self-support amount and any applicable relevant dependent child or multi-case deductions. This page applies only the common $31,046 self-support amount for 2026 and assumes the other deductions are zero.

The two child support incomes are combined. Each parent’s income percentage is their share of that combined amount. Care percentage is then converted to a cost percentage representing the share of the children’s costs met directly through care. Subtracting cost percentage from income percentage gives the child support percentage.

A positive percentage indicates that a parent is not meeting all of their income share directly through care and is the prospective payer. A negative percentage indicates the prospective receiving side. The page calculates both sides and displays the net direction, although the visible rail follows Parent A so the formula can be audited consistently.

When both child support incomes are zero, the page displays equal 50% income shares for a readable trail and the table produces zero child costs because combined income is zero. It does not decide whether a statutory minimum or fixed annual rate applies. That requires the official low-income provisions and the parent’s wider case facts.

Care percentage is converted through a statutory table

Care and cost are deliberately not identical at every point. A parent with regular care between 14% and 34% receives a 24% cost percentage because the formula recognises costs of maintaining care. In the shared-care bands, cost percentage moves progressively. Near the boundaries, one percentage point of care can therefore change the child support percentage materially.

Use the official care-percentage estimator or an established care decision. The number of nights is generally considered over a care period, and actual arrangements can be more complex than a weekly pattern. This page accepts the percentage as an input; it does not decide disputed care or apportion different patterns among different children.

If children have different care arrangements, Services Australia may calculate different child support percentages for each child. The single care input here is not suitable. Separate informal runs are not necessarily equivalent because the costs-of-children table also depends on the number and ages of all children in the assessment.

The 2026 costs-of-children table is progressive and capped

The annual cost amount depends on combined child support income, number of children and whether they are aged 12 or under, 13 or older, or a mixed-age group of at least two. The table uses income bands based on the 2026 annualised Male Total Average Weekly Earnings figure of $93,137. Its first breakpoint is half that figure, later breakpoints are multiples, and costs stop increasing above $232,843 combined child support income.

The calculator implements every 2026 band published on the Services Australia basic-formula page. It does not interpolate between annual tables or update values automatically. For a child support period starting in another calendar year, use that year’s formula values and costs table.

A worked example using the default inputs

Parent A has ATI of $90,000 and Parent B has $60,000. After deducting $31,046 from each, their child support incomes are $58,954 and $28,954, a combined $87,908. Parent A’s income percentage is about 67.06%. With 30% care, Parent A’s cost percentage is 24%, so Parent A’s positive child support percentage is about 43.06%.

For one child aged 12 or under, combined income falls in the second 2026 band. Annual child costs are $7,917 plus 15 cents for each dollar above $46,569. Multiplying those costs by Parent A’s positive percentage produces the basic annual transfer. The displayed monthly amount divides by 12, fortnightly by 26 and weekly by 52; actual collection timing and rounding may differ.

Adjusted taxable income is broader than salary

Child-support adjusted taxable income can include taxable income, reportable fringe benefits, target foreign income, total net investment losses, specified tax-free pensions or benefits and reportable superannuation contributions. It is not the amount deposited into a bank account and not necessarily the taxable-income field alone.

Services Australia normally uses income information under the statutory rules and may accept or make an estimate in relevant circumstances. Post-separation income, business structures, overseas income and incomplete tax returns can require special treatment. A new partner’s income is not simply added to a parent’s ATI, although relevant dependent children and other formula provisions can affect the parent’s child support income.

The 2026 self-support amount is one third of annualised MTAWE and is the same for both parents. It is updated each year on 1 January. Hard-coding $31,046 into a later-year calculation would produce the wrong child support incomes even if every other input stayed the same.

What can change an official assessment

Minimum annual and fixed annual rates can replace or modify a basic formula result for some low-income cases. The 2026 guide lists current values, but applying them requires facts not requested here. Protected earnings rules concern employer deductions and do not cap the assessment itself in this simple calculation.

Relevant dependent children and multiple child support cases can reduce child support income through calculated allowances rather than a user-chosen flat deduction. A child support agreement or court order can set different obligations. A parent may also seek a change of assessment for legislated reasons, including unusual costs or income, property and financial resources not adequately reflected by the formula.

Family Tax Benefit is not included in the transfer output. The published costs table represents net costs after Family Tax Benefit at the formula-design level, but the calculator does not estimate either parent’s family assistance. Private payments, school fees and non-cash maintenance may be credited only under the applicable rules or agreement.

Use the result to understand a formula trail or test the effect of one clearly defined input. For decisions, access the Child Support online account or official estimator and keep income and care details current. Seek legal advice for disputed parentage, care, agreements, court proceedings or property-settlement interaction.