Historic Tax Search Plan

This document outlines a strategy for gathering New Zealand tax rules and parameters for years prior to those already included in this repository.

Data Sources

1. data.govt.nz catalogue – query the public dataset catalogue for entries related to "income tax" or "tax rates". Many resources hosted by Inland Revenue are indexed here and provide machine-readable files.
2. Inland Revenue (ird.govt.nz) – inspect resource links discovered via the catalogue for historical spreadsheets or CSV files, such as historic income tax rates.
3. Legislation and government archives – for years not covered by available datasets, consult legislative archives (e.g. via legislation.govt.nz) and historical government publications.

Implementation Approach

The historic_tax_search.py utility automates the first step of this plan. It queries the data.govt.nz API, lists dataset titles and associated resource URLs, and can save results to disk for further analysis. Subsequent work involves reviewing these resources and converting relevant historical data into the repository's parameter format.