Choosing a withholding rate

Quick answer

Contractors who receive schedular payments have tax withheld at source, and you can elect your own withholding rate on the IR330C form you give each payer. There is a standard rate for your type of work, but you can choose higher or lower within limits.

The goal is simple: pick a rate close to your real average tax rate so that what is withheld during the year roughly matches what you actually owe. Get that right and your end-of-year tax is small or nil. The minimum you can usually elect is 10% (15% for non-resident contractors), and you can go higher voluntarily.

The detail, in plain English

Withholding is a credit against your final tax, not your final tax itself. You still file an IR3 and claim your business expenses; the amounts withheld during the year are credited against the total you owe.

Choosing a rate is a balancing act:

• Too low and not enough is withheld, leaving a lump sum to pay at year-end — and potentially pushing you into provisional tax next year.
• Too high and you over-withhold, effectively giving IRD an interest-free loan until your refund comes through.
• Just right is a rate near your average tax rate after expenses, so withholding tracks your real liability.

Two things shift the right number. First, expenses: if you have significant deductible costs, your taxable income is well below your gross pay, so a lower rate may fit. Second, other income: a salary or rental income on top can lift your marginal rate, so a higher withholding rate on contract work helps cover it. ACC levies also sit on top of income tax, so leaving a little headroom is sensible.

It helps to separate two different rates in your head. The withholding rate is applied to your gross schedular pay before expenses. Your real average tax rate applies to your net income after expenses. The two only line up when you account for the gap between gross and net, which is exactly why contractors with heavy expenses can comfortably elect a lower withholding rate than the headline figures suggest.

Your rate is not locked in for life either. You can lodge a new IR330C if your circumstances change — picking up a salaried job, taking on more expenses, or a big swing in turnover are all good reasons to revisit it mid-year rather than waiting for the bill.

A simple example

Take a contractor expecting $90,000 of schedular income with $15,000 of genuine expenses:

Electing a withholding rate near 20% on the gross would leave a small top-up at year-end (because tax applies to the $75,000 net, but withholding applies to the $90,000 gross). Electing close to that 22–24% average usually lands the year-end position near zero. Choosing the headline 33% top rate would over-withhold and tie up cash you could be using.

Common mistakes to avoid

• Defaulting to the standard rate and forgetting expenses. If you have real costs, the standard rate often over-withholds.
• Picking a rate that ignores your other income. A salary or rental on top can lift your real rate well above the contract default.
• Choosing a very low rate for cash flow. It feels good monthly but builds a year-end bill and can trigger provisional tax.
• Forgetting ACC. Levies are extra, so leave a little buffer rather than aiming for an exact zero.

One more trap: a brand-new contractor with no track record often guesses low to protect cash flow, then meets both a year-end bill and the first provisional-tax instalments at once. Setting a realistic rate from day one smooths that double hit out.

Where this fits in your return

Schedular payments and the tax withheld both appear on your IR3. The withholding is credited against your total tax, and your expenses reduce the income it is calculated on. If the withheld amounts fall short and your residual income tax exceeds $5,000, you move into provisional tax next year.

This builds directly on how schedular payments and withholding tax work in the first place.

How Fernway can help

We estimate your average tax rate after expenses and other income, recommend a withholding rate that lands your year-end near zero, and review it as your income changes. The point is no surprises — not the highest refund, just a rate that matches what you actually owe.

Book a free 20-minute review and we will help you set the right rate before you hand over your next IR330C.

This is general information only, not personalised tax advice. Your situation may differ, so confirm it with us or check ird.govt.nz.

In plain English: choose a withholding rate close to your real average tax rate after expenses, so what comes out during the year matches what you owe and July holds no surprises.