About NZTaxTools

NZ Tax Tools is an independent publisher of free New Zealand tax calculators and plain-English explainers — PAYE and income tax, the ACC earners' levy, KiwiSaver, student loan repayments, GST, Working for Families, property and investment tax. There is no sign-up, no paywall, and no paid tier. The aim is to give you an honest answer to a common New Zealand tax question and let you leave.

Who runs this site

NZ Tax Tools is an independent publication: New Zealand tax, pay, and retirement calculators built from official sources.

What stands behind the numbers is process: every rate and threshold is taken from the official source — Inland Revenue or the legislation that set it — locked in by an automated test suite, and dated on the page it appears on. When something is wrong, it goes on the corrections page and gets fixed at the source.

The site is funded by advertising served through Google AdSense. We take no affiliate commissions, sponsorships, or payments in exchange for coverage, and no advertiser sees or influences a calculator, an article, or a result before it is published.

Where the numbers come from

Every rate, threshold, bracket, contribution setting, and credit used in a calculation is taken from the body that set it, or from the legislation that changed it:

Inland Revenue (IRD) — guides, IR-number forms, and the tax-technical and tax-policy sites — for PAYE brackets and tax codes, student loan repayment settings, KiwiSaver, GST, the bright-line test, FIF rules, Working for Families, provisional tax, and use-of-money interest;
ACC and IRD's earners' levy pages for the levy rate and the earnings cap deducted through PAYE;
Work and Income (Ministry of Social Development) for benefit, supplement, and NZ Super rates;
MBIE and Employment New Zealand for the minimum wage and holiday pay rules, Stats NZ for the CPI series behind inflation tools, and the Reserve Bank for published interest rates;
the Treasury and Budget documents for announced changes, applied when they are confirmed;
legislation.govt.nz where the rule is statutory — the Income Tax Act 2007, the Accident Compensation (Earners' Levy) Regulations, and the amendment Acts that change them.

Secondary sources — news reports, accounting-firm summaries, competing calculators — are used for cross-checking only, never as the basis for a figure. Pages that carry a substantive number name the official documents behind it in a footer, so the claim can be checked rather than taken on trust. See Methodology & Sources for how the calculations are structured, and the Editorial Policy for the source hierarchy and review cadence.

How rates are versioned

New Zealand's tax year runs from 1 April to 31 March, so rules change on a different clock from the calendar year and from the Budget that announces them. They are not stored here as a single set of numbers that gets edited each April. They are stored per tax year, in one central configuration, and read from there by every calculator, reference page, and article that mentions them — so an IRD or ACC update lands in one place rather than being chased through prose.

Superseded years are kept rather than overwritten. Calculators that offer a tax-year selector compute an earlier year with that year's own rules, and a page written about a particular year stays pinned to that year after the year turns over, because someone filing or amending an earlier IR3 needs that year's answer. The calculators currently cover the 2024-25 to 2026-27 tax years.

How the calculations are checked

The calculation logic is written separately from the interface specifically so it can be tested, and it is — the full automated suite runs on every change before anything is published. The tests concentrate on where tax rules actually break:

boundary cases — the exact income at which a PAYE bracket, an abatement, or the ACC earnings cap starts, and the dollar either side of a threshold;
anchor cases — figures pinned to a published IRD or ACC number, such as the ACC earners' levy rate and earnings cap and the student loan repayment threshold, so an unintended edit to a rate fails the build;
regression cases — a confirmed error becomes a test asserting the right answer before it becomes a fix, so the same defect cannot come back unnoticed;
historical years — prior tax years are asserted as well as the current one;
a rollover smoke test that fails the build when a new tax year has been applied to some data files but not all of them.

The build itself is a gate as well as a compile step: it fails on a broken internal link, on a page nothing links to, on a calculator missing from the site's own index, and on an unannounced change to a page title or description.

What this site is not

Not a registered tax agent, and not a chartered accountant. Nothing here is prepared, reviewed, or signed by a chartered accountant, we cannot be linked to your myIR account, and we cannot act for you with Inland Revenue.
Not personal tax advice. What you get here is general information about how a published rule works, applied to figures you enter. It cannot tell you what to put in your own return, and it cannot account for every credit, deduction, or personal circumstance. For a binding answer, speak to a qualified tax adviser or contact IRD.
Not affiliated with Inland Revenue, ACC, Work and Income, or any government department. They are sources; none of them endorses, reviews, or is connected to this site.

Your data

Calculations run in your browser. The figures you type into a calculator stay on your device — this is a static site with no backend that could receive them. We use Google Analytics for anonymous, aggregate usage and Google AdSense for advertising, both covered by our Privacy Policy and Cookie Policy.

Corrections

If a figure here disagrees with Inland Revenue, ACC, or Work and Income, we want to know. Email contact@nztax.tools with the page URL, the inputs you used, and the official source that says otherwise. What happens after that is set out on our Corrections page.

Part of the TaxTools Network

NZ Tax Tools is part of the TaxTools Network — independent tax calculators and tools built from official government sources for Australia, Canada, New Zealand, the United Kingdom, and the United States.

The network sites do not share content or rebadge each other's calculators: each one implements its own country's rules on its own country's tax calendar, because a calculator that generalises across jurisdictions is wrong in all of them. What they share is the published standard they are built to and the methodology they follow.