PolicyEngine New Zealand

PolicyEngine New Zealand is a microsimulation model for New Zealand's tax and benefit system. It enables users to calculate the effects of taxes and benefits on households, and to simulate the impacts of policy reforms.

Features

• Comprehensive tax system: Income tax, ACC levies, GST
• Working for Families: Family Tax Credit, In-Work Tax Credit, Best Start
• Social security benefits: Jobseeker Support, NZ Superannuation, Sole Parent Support
• Additional support: Accommodation Supplement, Winter Energy Payment
• Retirement savings: KiwiSaver contributions and government support

Quick Start

pip install policyengine-nz

from policyengine_nz import NewZealandTaxBenefitSystem
from policyengine_core import Simulation

# Create system
system = NewZealandTaxBenefitSystem()

# Define a household
situation = {
    "people": {
        "person": {
            "employment_income": {"2025": 50000},
            "age": {"2025": 30}
        }
    }
}

# Run simulation
sim = Simulation(situation=situation, tax_benefit_system=system)
income_tax = sim.calculate("income_tax", "2025")
acc_levy = sim.calculate("acc_earners_levy", "2025")

print(f"Income tax: ${income_tax[0]:,.2f}")
print(f"ACC levy: ${acc_levy[0]:,.2f}")

System Coverage

Tax System (Inland Revenue Department)

• Personal Income Tax: Progressive rates (10.5%, 17.5%, 30%, 33%, 39%) with current thresholds
• ACC Earner's Levy: 1.67% on employment income up to $154,548 (2025)
• GST: 15% goods and services tax

Working for Families (Inland Revenue Department)

• Family Tax Credit: Up to $6,552 per child aged 0-15, $8,372 per child aged 16-18
• In-Work Tax Credit: $5,304 base rate (2025) for working families
• Best Start: $73 per week for children under 3 (income-tested after first year)

Social Security Benefits (Work and Income)

• Jobseeker Support: Up to $374.66 per week for single adults 25+ (2025)
• New Zealand Superannuation: Universal pension from age 65
• Sole Parent Support: Support for single parents
• Supported Living Payment: For people with disabilities
• Accommodation Supplement: Housing cost assistance (regional variations)
• Winter Energy Payment: Seasonal heating cost support

Retirement Savings

• KiwiSaver: Auto-enrolment scheme with 3% minimum contributions and government co-contribution

Data Sources

All parameters are sourced from official New Zealand government websites:

• Inland Revenue Department (IRD)
• Work and Income
• Ministry of Social Development
• New Zealand Treasury

Development

git clone https://github.com/PolicyEngine/policyengine-nz.git
cd policyengine-nz
make install
make test

Documentation

Full documentation is available at policyengine.org/nz/api

Contributing

We welcome contributions! Please see our developer guide for more information.

License

PolicyEngine New Zealand is licensed under the AGPL-3.0 License.

Acknowledgments

This project builds on the work of New Zealand Treasury's TAWA microsimulation model and other open source tax-benefit modeling efforts. We acknowledge the valuable research and data provided by:

• New Zealand Treasury Analytics & Insights team
• Statistics New Zealand
• Parliamentary Budget Office research
• Academic researchers in tax and social policy

Special thanks to the broader PolicyEngine community and OpenFisca ecosystem for providing the technical foundation for this work.