PAYECalculator.co.nz

The most common money question in a New Zealand job is also the simplest: what will I actually take home? The answer sits behind tax codes, the ACC earners’ levy, KiwiSaver rates and student loan thresholds, and most online calculators round them their own way.

PAYECalculator.co.nz answers that one question properly. It shows the payslip as an employer’s payroll would produce it, explains why a bonus or a second job looks over-taxed, and leaves nothing to sign up for.

The maths follows Inland Revenue’s payroll calculations and business rules specification, the document IRD publishes for payroll software developers, including how pay is annualised and truncated at each step. One engine runs in the browser and in an automated test suite, so the page and the tests can never disagree.

Before any change can be published, 41 test cases taken from IRD’s deduction tables and worked examples must match to the cent. The 16 guides take their worked examples from the same engine, so a guide can never quote a figure the calculator would not produce.

1. IRD specificationRates, thresholds and rounding rules
2. One tax engineThe same code in the page and the tests
3. 41 IRD test casesEvery case must match to the cent
4. Calculators and guides5 calculators, 16 guides

PAYECalculator.co.nz is new, launched on 10 November 2026, and we are plain about that: it has no track record of its own yet. What it does have is a method you can check, with every figure tested against Inland Revenue before it ships.

It is also the first of a set of focused New Zealand money sites built on the same engine, so the work done once here carries straight into the next tax and pay calculators.