Key takeaways

  • As a contractor, the IR330C tells your payer how much tax to deduct from your schedular payments. No form means a 45% no-notification rate.
  • NZ residents can choose any rate from 10% upwards. Non-residents have a 15% minimum.
  • You need a separate IR330C for each payer. The form is your responsibility, not theirs.
  • Withholding tax only covers income tax. ACC, GST, and student loan are separate.
  • A reasonable starting rate for most NZ-resident contractors earning $50,000 to $70,000 is around 20%.
  • The withholding tax deducted for contractors is not a final tax and if you choose a rate lower than your marginal tax rate, you will need to pay the additional tax direct to IRD.

If you are a contractor or freelancer in New Zealand, the IR330C is one of those forms you cannot afford to get wrong. Skip it or fill it in incorrectly, and your client or labour hire company is legally required to deduct tax at 45%. That is nearly half your pay, gone before you see it.

The form itself is not complicated. But the language on it is confusing enough that a lot of people either guess their way through or put it off until someone chases them. This guide walks you through every section so you can fill it out in five minutes and get on with your work.

What is the IR330C and who needs to fill one out?

The IR330C is a tax rate notification form for contractors. You fill it out and give it to whoever is paying you so they know how much withholding tax to deduct from your schedular payments before they pay you.

You need to complete one if you are a contractor or freelancer providing services through a labour hire company, recruitment agency, temping firm, or any organisation that makes schedular payments. If you work through multiple agencies or clients who deduct withholding tax, you need a separate IR330C for each one.

This form is your responsibility. Your payer cannot fill it out for you, and they are not allowed to advise you on what tax rate to choose. If they do not have a completed IR330C from you, they must deduct at the no-notification rate of 45%.

What goes in Section 1 of the IR330C?

Section 1 covers your details. Enter your full legal name exactly as it is registered with IRD. Then enter your IRD number. If you have an eight-digit IRD number, leave the first box blank and start from the second box. That is it for section 1. Two minutes.

What goes in Section 2 (and why it trips people up)?

Section 2 is the section that catches people out. There are two things to fill in.

Tax rate

You choose the percentage of tax to be withheld from your payments. The minimum is 10% for NZ tax residents and 15% for non-residents. Beyond that minimum, you can choose any rate you want; most contractors will follow the Standard Rate for your activity.

The IR330C includes a flowchart on page 2 to help you work out a sensible rate based on your expected income. If you hold an IRD certificate of exemption, you can enter 0%.

Getting this rate right matters. Choose too low and you will have a big tax bill at the end of the year, possibly with use-of-money interest on top. Choose too high and your cash flow suffers unnecessarily throughout the year. A reasonable approach is to estimate your total annual income from all sources, check which tax bracket that puts you in, and use a rate close to that marginal rate.

Activity number

This is a code that identifies the type of work you do, taken from the table on page 3 of the IR330C. Because the form is mandatory for labour-hire arrangements, most people completing it use activity number 19, the labour-hire number. Film and television workers use 24. If your work is not a labour-hire arrangement, choose the number that matches what you actually do from the page 3 table. The activity number does not change the amount of tax you end up paying, so the main thing is to pick the closest match. If you are not sure, ask the company paying you. They deal with contractors regularly and will know.

What goes in Section 3?

Section 3 is the declaration. Enter your full name again (make sure it matches Section 1), your title or designation (leave this blank if you are an individual contractor or sole trader), sign it, and date it. If you filled in the form on your computer, an electronic signature is fine. Save it as a PDF and send it to your payer.

How do I choose the right tax rate for my situation?

A practical way to choose your rate:

  • Estimate your total expected income for the year, including any PAYE salary, contracting income, and other sources.
  • Subtract your expected business expenses to find your taxable income.
  • Check which tax bracket that figure puts you in.
  • Choose a withholding rate close to that marginal bracket.

Example: a contractor expecting $80,000 of contracting income with $10,000 of expenses sits at $70,000 taxable. That puts them in the 30% bracket. A 30% withholding rate is a reasonable starting point. If they also have a $50,000 PAYE salary, the combined income hits the 33% bracket on the contracting portion, so 33% would be more accurate and will minimise how much additional tax would be payable at the end of the year.

Where do I get the IR330C form?

Download the IR330C directly from ird.govt.nz. Search for IR330C or go to the forms section. You can fill it in digitally or print and complete by hand. Most contractors keep a saved digital copy and update it whenever their circumstances change.

What does withholding tax actually cover?

Withholding tax covers income tax only. It does not cover:

  • GST (if you are registered, you still file GST returns separately).
  • ACC levies (you receive separate ACC invoices each year).
  • Student loan repayments (calculated when you file your IR3).
  • KiwiSaver contributions (your responsibility).

Each of these sits outside the withholding tax system and needs to be managed separately. People sometimes assume withholding tax covers everything because it feels similar to PAYE. It does not.

What happens at year-end if my withholding rate was wrong?

You still need to file an IR3 individual tax return at the end of the financial year, even if withholding tax has been deducted from all your income. The withholding tax is credited against your final tax bill on your return.

If your withholding rate was too low, you owe the difference. If it was too high, you get a refund. Getting the rate close to your marginal bracket saves you from cash flow surprises in either direction.

If your residual income tax ends up over $5,000, you will enter the provisional tax system the following year. Choosing too low a withholding rate makes this more likely.

How can I get a more accurate rate using real-time tools?

Afirmo’s real-time tax calculations can help you estimate your total tax position across all income sources, so you can choose a withholding rate with more confidence. As your income changes through the year, you can update your IR330C with each payer to better match your true marginal rate.

You can submit a new IR330C at any time. Your payer just uses the most recent one on file. There is no penalty for updating mid-year.

Frequently asked questions

What happens if I do not submit an IR330C?

Your payer must deduct tax at the no-notification rate of 45%. That continues until you submit a completed form, at which point the new rate applies to future payments. You cannot recover the 45% rate retrospectively, though it does get credited against your final tax bill at year-end.

Can I use a different tax rate for different clients?

Yes. You submit a separate IR330C to each payer and you can choose a different rate for each one. This rarely makes sense in practice (your total marginal rate is what matters at year-end), but it is allowed.

Do I still file an IR3 if all my tax has been withheld?

Yes. You file an IR3 at year-end declaring all your income, claiming your business expenses, and reconciling against the tax already withheld. The withholding tax is treated as a credit on your return.

Can I change my withholding rate during the year?

Yes. Submit a new IR330C to your payer with the updated rate. They apply it to future payments. There is no limit on how often you can update your rate, though once or twice a year is usually enough unless your income changes substantially.

Afirmo helps contractors track their full income picture and pick a withholding rate that matches their actual tax position. Start a free trial at afirmo.com.