Child Support in New Zealand: How Inland Revenue Calculates It

Child support in New Zealand is worked out by Inland Revenue (IRD) using a set formula, not by a judge deciding a fair amount case by case. This page explains what goes into that formula and where the current figures come from.

This is general information about New Zealand law, not legal advice. For your own situation, consult a lawyer or your local Community Law centre.

Who calculates child support in New Zealand

Child support is administered by Inland Revenue under the Child Support Act 1991, not by the Family Court. IRD assesses, collects, and pays out child support using a formula that applies the same set of rules to every case, rather than a judge weighing up what is fair on the facts.

This is a separate process from decisions about day-to-day care or contact with a child, which are generally dealt with under the Care of Children Act 2004. A parent's share of care can feed into the child support formula, but the formula does not decide who a child lives with.

Three ways child support can be arranged

IRD recognises three ways of arranging child support: a private arrangement between the parents with no IRD involvement, a voluntary agreement registered with IRD, or a formula assessment carried out by IRD. This page focuses on the formula assessment, which is the default and the most common of the three.

Parents who prefer to manage payments themselves can use a private arrangement, and can move to a voluntary agreement or a formula assessment at any time. A voluntary agreement is a more formal, written option, registered with IRD on the required form.

Step 1: Each parent's income and the living allowance

The formula starts with each parent's income, generally their taxable income from the previous year. From that, IRD deducts a living allowance, an amount of a parent's own income that is set aside before child support is calculated, on the basis that the paying parent has to live too.

For the 2026/27 tax year, the standard living allowance is $30,557, or $34,252 for a parent receiving a supported living payment. A parent supporting other dependent children, or supporting more than one child support group, can also have a dependent child allowance or multi-group allowance applied, which further reduces their child support income. What remains after these deductions is that parent's child support income.

Step 2: Combining incomes and the income percentage

IRD adds both parents' child support incomes together to get the combined child support income. Each parent's own child support income, as a share of that combined figure, is their income percentage.

The child expenditure table used in the next step has six income brackets, and its highest bracket begins at $214,855 for 2026/27. Combined child support income above that level is still assessed using the top bracket, so the formula's estimate of a child's cost does not keep rising once combined income reaches that point.

Step 3: Care and the cost percentage

The formula also takes into account how much time each parent has the child in their care, measured in nights per year. Care of at least 28% of nights, about 103 nights a year, is needed before it is recognised in the formula at all.

Where a parent has less than 28% care, the other parent is treated as having full ongoing care for cost purposes. A parent generally needs care of at least 35%, about 128 nights a year, to be treated as a receiving carer able to receive child support rather than a parent who pays it. Between those points, and above them, an increasing share of care reduces what a parent contributes and can shift some or all of a formula amount the other way.

Step 4: The child expenditure table

The final dollar figure comes from IRD's child expenditure table, which estimates the average annual cost of raising children in New Zealand. The table has two age bands, children aged 12 and under, and children aged 13 and over, each split across six income brackets, and child support is reassessed when a child turns 13.

Where a parent has more than one qualifying child, the table's cost estimate for the relevant income bracket is generally divided across the children in that age band. Combining the income percentage, the care cost percentage, and the relevant expenditure table figures produces the annual formula assessment for each parent.

The minimum annual amount

IRD applies a minimum annual amount of child support, $1,211 for the 2026/27 tax year. Where the formula would otherwise work out to less than this floor for a liable parent, IRD generally applies the minimum amount instead, subject to limited statutory exceptions.

These figures change every year

The living allowance, the income cap, the minimum annual amount, and the child expenditure table are all reviewed by IRD and generally updated each 1 April, in line with movements in average wages and inflation. A figure that was correct for an earlier tax year will not necessarily still be correct, so any specific calculation should be checked against IRD's current tables, or IRD's own assessment for a parent's actual circumstances.

Related New Zealand family law topics

For how relationship property, as opposed to child support, is divided when a relationship ends, see the 3-year rule for relationship property. For the wider picture of family law in New Zealand, see the family law hub.