NZ Child Support Calculator
This calculator estimates how much child support you might pay or receive in New Zealand, using a simplified version of the 8-step IRD formula assessment set out in the Child Support Act 1991. Child support matters because it is worked out from both parents' incomes and how care is shared, not from a fixed rate, so small changes in nights or income can shift who is liable and by how much. You enter each parent's annual taxable income, which living allowance applies to them, the number of nights per year the child stays with you, any other dependent children in your household, the child's age band, and how many children are covered by the arrangement. The calculator then works through living allowances, child support income, income percentages and care cost percentages to show who pays, the estimated monthly, weekly and annual amount, and a full breakdown of each parent's calculation including their income percentage, care cost percentage and final child support percentage. Use it to get a realistic idea of your likely payment or entitlement before applying for a formal assessment, and try different nights or income figures to see how care arrangements affect the outcome. This is a simplified estimate only, so treat the figures as indicative and confirm your actual assessment using the official IRD child support calculator or a formal application.
1. Parent A (You)
2. Parent B (Other Parent)
Parent A Calculation
Parent B Calculation
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 (1 April 2026 to 31 March 2027)
| Situation | Annual Amount |
|---|---|
| Standard living allowance (most people) | $30,557 |
| Parent receiving a Supported Living Payment | $34,252 |
The living allowance no longer changes according to whether you are single or living with a new partner. That split belonged to the pre-2015 formula. Since 1 April 2015 there is one standard living allowance for most people, with a higher allowance only for parents receiving a Supported Living Payment. The amounts are set from benefit rates and updated by IRD each year on 1 April. They make sure a parent retains enough income for basic living costs before child support is calculated. Separate dependent child and multi-group allowances can also apply on top of the living allowance.
Care Cost Percentages
| Proportion of Care (nights) | Care Level | Care Cost % |
|---|---|---|
| 0% to 27% (up to about 100 nights) | No recognised care | Nil |
| 28% to 34% (about 103 to 124 nights) | Regular care | 24% |
| 35% to 47% (about 128 to 172 nights) | Regular care | 25% plus 2% for each percentage point over 35% (25% to 49%) |
| 48% to 52% (about 175 to 190 nights) | Shared care | 50% |
| 53% to 65% (about 193 to 237 nights) | Substantial care | 51% plus 2% for each percentage point over 53% (51% to 75%) |
| 66% to 72% (about 241 to 263 nights) | Primary care | 76% |
| 73% to 100% (about 266 nights or more) | Primary care | 100% |
These bands come from Schedule 2 of the Child Support Act 1991. Recognised care starts at 28% of nights, which IRD describes as about two nights a week or roughly 103 nights a year. Below 28% the care cost percentage is nil. The separate 35% figure (about 128 nights) is the threshold a parent or carer has to reach before they can be paid child support as a receiving carer, not the threshold at which care is recognised in the formula.
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).
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Sources: Child Support Act 1991, including Schedule 2 care cost percentages and Schedule 3 expenditure on children (legislation.govt.nz). IRD child support annual rates for 1 April 2026 to 31 March 2027, giving the $30,557 standard living allowance, the $34,252 Supported Living Payment living allowance and the $1,211 minimum annual child support (ird.govt.nz/child-support/types/formula-assessment/amount/annual-rates). IRD guidance on sharing care of children (ird.govt.nz/child-support/types/formula-assessment/sharing-care).
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.