How is child support calculated in NZ?

NZ child support uses an 8-step IRD formula. Each parent's taxable income is reduced by a living allowance (based on benefit rates). The remaining 'child support income' is combined, and each parent's percentage of the total is calculated. Care cost percentages are determined by how many nights the child spends with each parent. The income percentage minus the care cost percentage gives the child support percentage. This is multiplied by the child's estimated cost (from IRD expenditure tables based on age and combined income) to give the annual child support amount.

What is the living allowance for child support?

The living allowance is deducted from each parent's income before the child support calculation. For the 2026/27 year, the living allowance for a single parent is approximately $25,270 per year. For a parent living with a new partner, it is approximately $21,133. These amounts are based on benefit rates and are updated annually by IRD. If your income after deducting the living allowance is zero or negative, your child support income is treated as nil.

How does shared care affect child support?

Care is measured by the number of nights per year the child spends with each parent. If a child spends at least 128 nights per year (35%) with a parent, that parent has 'recognised care' and their care costs are factored into the formula. More nights means a higher care cost percentage, which reduces the amount that parent pays (or increases what they receive). If the child spends less than 128 nights with a parent, that parent has no recognised care for formula purposes.

What is the minimum child support payment?

The minimum annual child support payment for the 2026/27 year is approximately $929 (about $18 per week or $77 per month). This applies when a liable parent's calculated amount falls below the minimum. Even parents with very low incomes or on benefits are required to pay at least this minimum amount.

Can I use IRD's own child support calculator?

Yes. IRD provides an official child support calculator at ird.govt.nz/child-support/how-much-you-might-get-or-pay/calculator. It is the most accurate tool as it uses the exact current expenditure tables and living allowance figures. The calculator on this page provides a simplified estimate to help you understand the formula and get an approximate figure, but you should use the IRD calculator or apply for a formal assessment for definitive amounts.

NZ Child Support Calculator

Estimate your child support payment or entitlement using the IRD formula assessment. This calculator uses a simplified version of the 8-step IRD formula based on both parents' incomes, the child's age, and care arrangements. For a definitive calculation, use the official IRD child support calculator or apply for a formal assessment.

Updated April 2026 Living allowances and expenditure tables for 2026/27 year. Child Support Act 1991 as amended.

1. Parent A (You)

Your annual taxable income

Your living situation

Nights per year child lives with you

nights

Other dependent children living with you (not this child)

children

2. Parent B (Other Parent)

Their annual taxable income (best estimate)

Their living situation

Child's age

Number of children in this child support arrangement

Estimated Child Support

Who Pays

Liable parent

Monthly
-
Estimated payment

Weekly

Estimated

Annual

Estimated

Parent A Calculation

Taxable income-

Living allowance-

Child support income-

Income percentage-

Care (nights)-

Care cost percentage-

Child support percentage-

Parent B Calculation

Taxable income-

Living allowance-

Child support income-

Income percentage-

Care (nights)-

Care cost percentage-

Child support percentage-

Estimate: -

How the Child Support Formula Works

New Zealand uses an income-shares model administered by Inland Revenue (IRD) under the Child Support Act 1991 (as amended 2013). The formula estimates the cost of raising a child and divides it between parents based on their incomes and care arrangements. The calculation follows 8 steps:

Step 1: Work out each parent's adjusted taxable income
Step 2: Subtract the living allowance (and any dependent child or multi-group allowances) to get child support income
Step 3: Add both parents' child support incomes to get combined income
Step 4: Calculate each parent's income percentage of the combined total
Step 5: Determine the care cost percentage based on nights per year
Step 6: Subtract care cost percentage from income percentage to get the child support percentage
Step 7: Look up the child's estimated cost from the expenditure table (based on age and combined income)
Step 8: Multiply the positive child support percentage by the child's cost

A parent with a positive child support percentage is the liable parent (pays). A parent with a negative percentage is the receiving carer.

Living Allowances (2026/27)

Situation	Annual Amount
Single parent (no new partner)	~$25,270
Parent living with new partner	~$21,133

Living allowances are based on benefit rates and updated annually by IRD. They ensure a parent retains enough income for basic living costs before child support is calculated.

Care Cost Percentages

Nights per Year	Care Level	Cost %
0-51 (0-13%)	No recognised care	0%
52-127 (14-34%)	Regular care	0% (below threshold)
128-175 (35-47%)	Regular care	25%
176-225 (48-61%)	Substantial care	50% approx
226-262 (62-71%)	Primary care	75% approx
263-365 (72-100%)	Primary care	100%

Care must be at least 128 nights per year (35%) for it to be "recognised care" that affects the formula. Below 128 nights, the care cost percentage is 0%.

Important Limitations

This calculator uses a simplified version of the expenditure tables. The actual IRD tables have detailed income bands and are updated annually.
Dependent child allowances and multi-group allowances are applied in simplified form only.
For definitive amounts, use the official IRD calculator or apply for a formal assessment.
Income used is generally taxable income from the last calendar year (PAYE earners) or net income from 2 years ago (IR3 filers, adjusted for inflation).

Related Calculators

Sources: Child Support Act 1991 (legislation.govt.nz). IRD child support formula assessment (ird.govt.nz/child-support). IRD child support rates and expenditure tables 2026/27 (ird.govt.nz). IRD form IR100 April 2026.

This calculator provides a simplified estimate only. Child support is complex and the actual amount depends on verified income, the specific expenditure table bands, dependent child allowances, multi-group situations, and other factors. Use the IRD calculator at ird.govt.nz for accurate figures, or apply for a formal assessment. This tool does not send any information to IRD.