Secondary Tax and a Second Job

🔢 Why a Second Job Is Taxed Differently

If you take a second job, the tax on it can look alarmingly high, and many people wrongly believe they are being punished for working more. You are not. Secondary tax simply makes sure the tax on your combined income is collected properly across the year. Understanding it stops the panic and helps you pick the right code.

                Key Point: New Zealand's low-income threshold, where the first slice of income is taxed at the lowest rate, can only be claimed once. Your main job claims it through the M tax code. A second job uses a secondary code, which withholds at a higher rate because it cannot claim that threshold again. This is not extra or double tax. It is just collecting the right amount up front. At year end, Inland Revenue squares up your actual total income against what was withheld, refunding or billing the difference.
            

The Threshold Can Only Be Used Once

Income tax is progressive, so the first part of your income is taxed at the lowest rate, then higher slices at higher rates. That low-rate slice belongs to your total income, not to each job. If both jobs claimed it, you would underpay.

Your main job claims the low-rate threshold with the M code

Your second job sits on top of your main income

So its first dollar is already past the low-rate slice

The secondary code withholds at the rate that fits that higher band

🏷️ Choosing the Right Secondary Code

Secondary Codes Reflect Your Combined Income

The secondary tax code you pick should reflect your total income across all jobs, so the second job is taxed at the rate that matches the band it falls into. The codes step up as combined income rises.

Combined Income Band	Idea
Lowest band	A lower secondary rate
Middle bands	A middle secondary rate
Higher bands	A higher secondary rate

Inland Revenue publishes the current secondary codes and the income bands they apply to. Picking the code that matches your combined income keeps the withholding close to what you actually owe.

The Tailored Tax Code Option

If a standard secondary code withholds clearly too much or too little for your situation, you can apply to Inland Revenue for a tailored tax code. This sets a rate matched to your circumstances, smoothing out the year rather than waiting for a refund or bill.

                If the standard code feels wrong: A tailored tax code can prevent large over-deductions during the year. It is worth considering if your second job is small, or your situation does not fit the standard bands neatly.
            

Add Any Student Loan or KiwiSaver

Your secondary income may also have student loan repayments and KiwiSaver deducted, depending on your codes and choices. These are separate from income tax but also reduce the take-home from the second job.

⚖️ The End-of-Year Square-Up

Why Withholding Is Not the Final Word

Secondary tax is a withholding estimate, not your final tax. After the tax year, Inland Revenue brings together income from all your jobs, works out the actual tax owed on the total, and compares it with everything that was withheld.

IRD receives income details from all your employers

It calculates the real tax on your combined income

It compares that with the total tax withheld

You get a refund if too much was taken, or a bill if too little

What This Means in Practice

Over-withheld: If your secondary code took more than needed, you receive a refund after the square-up.
Under-withheld: If too little was taken, you may have a bill, so it is wise not to spend as if the headline take-home is yours to keep.
Right code, smoother year: Choosing the correct code keeps the square-up small.

                Secondary tax is not lost money: Because of the year-end square-up, paying a bit too much through a secondary code is not money gone forever. It comes back as a refund. The goal is to get the code right so you are neither lending the government money interest-free nor facing a surprise bill.
            

💡 Avoiding Problems and Common Myths

Myth 1: Secondary Tax Is a Penalty

It is not. It just collects the right amount on income stacked on top of your main job. Working more always leaves you better off overall.

Myth 2: Both Jobs Should Use the M Code

This is the most common and costly error. Using M on two jobs claims the low-income threshold twice, so you underpay through the year and face a bill at the square-up.

Myth 3: A Second Job Is Not Worth It Because of Tax

Even on a higher secondary rate, you keep the large majority of what you earn. The extra income is still well worth having.

Myth 4: You Cannot Change Anything

You can pick a code that matches your combined income, or apply for a tailored code if the standard one is clearly wrong. You are not stuck.

A Simple Approach

1. Use the M code on your main job only

2. Use a secondary code on the second job that matches your combined income

3. Consider a tailored code if the standard one over-deducts

4. Do not spend the second job's pay as if no further tax is due

5. Check the year-end square-up for a refund or bill

For the underlying tax brackets, see our Progressive Tax System guide, and use the PAYE Calculator to estimate take-home pay across jobs.

Final word: Secondary tax can look harsh, but it is just the system collecting the right tax on income stacked above your main job, with a year-end square-up to put things right. Keep the M code on your main job, choose a secondary code that matches your combined income, and consider a tailored code if needed. This is general information, not personalised advice, and the codes and bands can change, so check the current details.

🎯 Test Your Knowledge

Quiz on Secondary Tax (20 Questions)

1. Secondary tax exists because:

The low-income threshold can only be claimed once

The government punishes extra work

Second jobs are illegal

Banks require it

2. Your main job uses which tax code?

A secondary code

GST

No code

3. A second job uses:

A secondary tax code

The M code as well

No tax at all

Your IRD number only

4. Secondary tax is:

Not extra or double tax, just correct withholding

A penalty for working more

Double the normal tax

Optional

5. The secondary code you choose should reflect:

Your total income across all jobs

Only the second job's pay

Your age

Your bank balance

6. If a standard secondary code over-deducts, you can:

Apply for a tailored tax code

Stop paying tax

Quit the job only

Do nothing, it is fixed

7. Using the M code on two jobs:

Claims the threshold twice and underpays, causing a bill

Is the recommended setup

Gives a bigger refund

Has no effect

8. At year end, Inland Revenue:

Squares up actual tax against what was withheld

Ignores secondary income

Doubles your tax

Refunds everyone the same amount

9. If too much was withheld, you:

Receive a refund after the square-up

Lose the money

Pay a penalty

Get nothing

10. If too little was withheld, you:

May have a bill to pay

Always get a refund

Pay nothing more ever

Lose your job

11. Income tax in NZ is:

Progressive, with higher slices taxed at higher rates

A single flat rate

Zero on second jobs

Set by your employer

12. The low-rate slice of income belongs to:

Your total income, not each job separately

Every job individually

Only your second job

Your employer

13. Even on a higher secondary rate you:

Keep the large majority of what you earn

Keep nothing

Pay over 100% in tax

Earn less than nothing

14. Secondary income may also have deducted:

Student loan and KiwiSaver, depending on your situation

Nothing ever

GST

Your rent

15. Secondary tax paid through the year is:

Not lost; over-payments come back as a refund

Gone forever

A fine

Paid to your employer

16. Choosing the correct secondary code:

Keeps the year-end square-up small

Makes no difference

Doubles your tax

Cancels your main job's code

17. Where do you find current secondary codes and bands?

Inland Revenue publishes them

On your power bill

Nowhere

From your flatmates

18. With a second job you should avoid:

Spending its pay as if no further tax is due

Working at all

Telling IRD your income

Choosing any code

19. A tailored tax code is useful when:

The standard code over-deducts or does not fit your situation

You want to avoid all tax

You have only one job

Never

20. The overall message on secondary tax is:

It is correct withholding, not a penalty, with a year-end square-up

It makes a second job pointless

It is double tax forever

It cannot be changed

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