New Zealand Secondary Tax Codes and the Myth About Them

New Zealand's income tax is straightforward: five rates rising from 10.5% to 39%, with no tax free threshold and an ACC earners' levy charged alongside. PAYE is deducted by employers using a tax code declared by the employee.

The complication arises when someone has more than one source of employment income, because neither employer can see the other.

Why the secondary code looks harsh

The primary code applies the rate scale from the bottom, so the first slice of income is taxed at 10.5%. If a second employer also started from the bottom, the low rates would be applied twice and tax would be underdeducted.

The secondary code prevents this by applying a rate appropriate to income that sits on top of your primary income. Because that rate does not include the lower steps, it looks high in isolation. It is not an extra tax, it is the correct rate for the position that income occupies.

Code	When it is used	What it does
M	Primary job, main source of income	Applies the rate scale from the bottom
ME	Primary job, where the independent earner tax credit applies	As above, plus the credit
SB, S, SH, ST, SA	Secondary sources, by estimated total income band	Applies a flat rate matching the band the extra income falls into
Tailored tax code	Any situation where the standard codes give the wrong result	A rate calculated by Inland Revenue for your circumstances
No declaration filed	Where the employee has not completed the form	Withholding at the no-notification rate, which genuinely is punitive

The last row is where the real damage happens. Failing to complete the tax code declaration leads to withholding at a rate well above anything the standard codes produce, and it is entirely avoidable.

Choosing the right secondary code

The secondary codes are banded by your total estimated income from all sources. Choosing a band that is too low results in underdeduction and a bill at assessment. Choosing one that is too high results in overdeduction and a refund.

Estimate total annual income from every source.
Select the secondary code matching that total, not the income from the secondary job alone. This is the step most often got wrong.
If income varies unpredictably, apply for a tailored tax code, which Inland Revenue calculates specifically.
Review at the start of each tax year on 1 April, and whenever a job starts or ends.

The automatic assessment changed the picture

New Zealand introduced automatic income tax assessment for most salary and wage earners. Inland Revenue calculates the year's position from employer filings and issues a refund or a bill without the individual doing anything.

This removed most of the historic harm from secondary tax, because an incorrect code now produces a temporary cash flow effect rather than a permanent loss. Someone overtaxed on a second job receives the difference back after the tax year ends on 31 March.

The wider pattern of countries that assess automatically is in which countries refund automatically, and the general second job problem in taking a second job.

The student loan interaction

Student loan repayments are deducted at a set percentage above a repayment threshold, and the threshold is applied to the primary job. A secondary job carries a student loan deduction from the first dollar unless a repayment exemption has been granted.

An exemption is available where total income is below the annual threshold, and applying for it is worthwhile for anyone with two small jobs. The general position on payroll collected student loans is in student loan repayments through payroll.

The tax due depends on total income, not on which job it came from. Enter the combined figure on the New Zealand Salary Calculator.