Methodology

About FinLab

FinLab provides four connected calculators: take-home pay, KiwiSaver first-home withdrawal, borrowing range and mortgage repayments. The aim is clear estimates from published rules — not product sales.

FinLab is not affiliated with any bank, lender, KiwiSaver provider or government agency. It does not sell leads or take referral fees. Calculations run in your browser. FinLab is not a licensed Financial Advice Provider — see the disclaimer.

Data sources

FinLab does not invent rates. Tax, levy, KiwiSaver, student loan, DTI, LVR and first-home figures are taken from official publications:

• Inland Revenue (IRD)
• Reserve Bank of New Zealand (RBNZ)
• Kāinga Ora
• New Zealand legislation and Budget documents

Each value is stored in versioned data with an effective date and a link to its official source. Full tables are on the reference pages.

How calculations work

Each calculator applies published rules to the numbers you enter. All math runs in your browser. The tools cannot apply a lender's internal policy, assess creditworthiness, or replace a payslip, loan offer or provider statement. Results are estimates.

Interest rates and bank stress-test rates in the mortgage and borrowing tools are editable defaults, not official market rates. Change them to match current offers.

Updates

Rule files are versioned. They are updated when an official source announces a change, and reviewed around 1 April each year when tax-year settings typically move. If a FinLab figure and an official source disagree, the official source prevails.

Corrections

If a figure is incorrect

• Incorrect values are corrected in the data file and deployed as soon as practical.
• Source links and effective dates are updated with the correction.
• Material corrections that could change a decision are noted on this page.

Reporting an issue

Note the calculator, the figure that looks wrong, and the official source you compared against.

What is not an error

• A bank or provider reaching a different decision — their criteria differ.
• Editable assumptions (interest rates, stress-test rates) — they are starting points.
• An estimate that is not a guarantee or approval.