Child Support Calculator
Estimate NZ child support liability using the IRD 8-step formula. Factors in living allowance, dependent children, and share of care.
About this calculator
This calculator implements IRD child support 8-step formula from Inland Revenue (IRD). Last consulted 18 May 2026. Verify the figures yourself by following the link.
NZ Child Support formula parameters
FY 2026-27 IRD formula- •Living allowance (single): $24,000
- •Per dependent child: +$11,500
- •Cost of 1 child %: 17%
- •Cost of 2 children %: 24%
- •Cost of 3+ children %: 27%
- •Shared care threshold: 28% of nights (103+/yr)
- •Minimum annual liability: $1,230
Source: IRD — Child Support
Disclaimer
This calculator provides estimates for general information purposes only. Results should not be relied upon as professional financial, tax, or legal advice. Tax rates and thresholds are based on publicly available IRD data and may change. Always consult a qualified tax agent or financial adviser for advice specific to your circumstances.
How NZ Child Support is calculated (IRD 8-step)
ATI − living allowance × cost-of-children % × share-of-care reduction = liability.
- 1
Adjusted taxable income (ATI)
ATI = taxable_income + add-backs (rental losses, fringe benefits)
Uses prior tax year by default.
- 2
Living allowance
Allow = $24,000 single + ($10,500 if partnered) + ($11,500 × dep_children)
Indexed annually.
- 3
Child support income
CS_income = max(0, ATI − living_allowance)
If negative, only minimum applies.
- 4
Cost of children %
Cost_% = 17% (1 child) / 24% (2) / 27% (3+)
Of CS_income.
- 5
Share of care reduction
Care_pct = nights ÷ 365 × 100 — reduces liability proportionally above 28%
Tiered: 13-27% = 24% reduction, 28-72% = pro-rata.
- 6
Final liability
Annual = max($1,230 minimum, base × (1 − care_reduction))
Minimum $1,230/yr (2026).
Worked example
Inputs: ATI $80k, single, 2 dep children, 1 CS child, 50 care nights
Result: Allow $35,500. CS income $44,500. Base $44.5k × 17% = $7,565. Care 14% → no reduction. Annual $7,565.
Frequently Asked Questions
How is NZ child support calculated?
Can parents agree on a different amount?
How this calculator works
This child support calculator uses the latest data from official New Zealand government sources to provide accurate results. All calculations are performed in your browser — your data never leaves your device.
All calculations are performed in your browser — your data never leaves your device. Results are for general guidance only and should not be considered professional financial advice.
Built and maintained by Konstantin Iakovlev. Data sourced from the IRD and official New Zealand government sources.
Last reviewed: