Provisional tax is how New Zealand businesses and self-employed people pay income tax during the year instead of in one lump at the end. It’s sensible in principle — but choose the wrong option for your business and it can drain cash at exactly the wrong time. Here’s how the four options work, with Inland Revenue’s current rules.
Do you have to pay provisional tax?
You’ll pay provisional tax if your residual income tax (RIT) for the previous year was more than $5,000. RIT is your income tax after tax credits such as PAYE already deducted.
Below $5,000, you just pay your tax after the year ends (terminal tax).
Option 1: standard
How it’s calculated: last year’s RIT plus 5%. If last year’s return isn’t filed yet when an instalment falls due, it’s RIT from two years ago plus 10%.
When you pay (31 March balance date):
- 28 August, 15 January and 7 May — three instalments;
- or 28 October and 7 May — two instalments if you file GST six-monthly.
Suits: businesses with steady or rising income that want simplicity.
Watch for: if your income jumps, you’ll have extra terminal tax to pay after year-end. If it falls, you may overpay during the year and wait for a refund.
Option 2: estimation
How it’s calculated: you estimate this year’s RIT yourself, and can revise the estimate up to your final instalment.
When you pay: the same instalment dates as standard.
Suits: businesses whose income will clearly be lower (or very different) this year — for example after losing a major contract or a tough season.
Watch for: you must estimate “fairly and reasonably”. If you underestimate, use-of-money interest can apply on the shortfall. Keep notes on how you arrived at your estimate.
Option 3: ratio
How it’s calculated: Inland Revenue sets a ratio percentage based on your previous RIT and GST turnover. Each instalment is that percentage of your GST taxable supplies for the period — so tax rises and falls with sales.
Eligibility:
- RIT greater than $5,000 and up to $150,000;
- you file GST monthly or two-monthly;
- in business and GST-registered for the whole previous year and part of the year before;
- not available to partnerships;
- you must elect before the year starts.
When you pay (31 March balance date): six instalments — 28 June, 28 August, 28 October, 15 January, 28 February and 7 May.
Suits: seasonal businesses with a stable margin, where sales drive profit fairly predictably.
Option 4: AIM (accounting income method)
How it works: approved accounting software calculates provisional tax from your actual year-to-date results each period, and you pay with your GST return (or on the AIM dates). If you make a loss in a period, you generally don’t pay.
Eligibility: individuals and companies with turnover under $5 million, using AIM-capable software.
When you pay: in line with your AIM statements — for a 31 March balance date, two- or six-monthly GST filers pay six instalments on the same dates as the ratio option, while monthly GST filers may be able to pay more often.
Suits: businesses with irregular income, new or fast-growing businesses, and anyone who wants tax paid as profit is actually earned.
Watch for: you need to keep the books up to date every period. You must actively choose AIM each year.
Side by side
| Option | Based on | Best for | Main risk |
|---|---|---|---|
| Standard | Last year’s RIT + 5% | Steady, predictable income | Big terminal tax if income jumps |
| Estimation | Your forecast | Income clearly dropping | Interest if you underestimate |
| Ratio | % of GST turnover | Seasonal, stable margins | Eligibility limits |
| AIM | Actual year-to-date profit | Irregular or growing income | Needs current books |
Terminal tax: the other bill
Whatever option you use, any balance after your return is assessed is terminal tax, due on 7 February of the following year for a 31 March balance date — or 7 April if you have a tax agent with an extension of time.
Matching provisional tax to cash flow
The best option is the one that puts tax payments where your cash actually is:
- A café with steady weekly takings → standard is usually fine.
- An orchard or tourism operator with lumpy income → ratio or AIM can smooth things.
- A builder coming off a bumper year into a quieter one → estimation, with care.
- A start-up growing fast → AIM avoids paying tax on profit you haven’t made yet.
Whichever you choose, set aside a weekly amount. The GST & provisional tax planner calculates the standard option and combines it with GST into one weekly figure.
If you’ve fallen behind
Missed instalments attract penalties and interest, and they compound with GST and PAYE arrears. Options include an instalment arrangement with IRD or clearing the debt with a business loan — with a property-secured loan, IRD debt can be refinanced or paid out. Read dealing with IRD debt or see IRD tax debt funding.
This guide is general information. Your accountant or tax agent should confirm which option suits your business.
Talk to a lending specialist if tax timing is squeezing your cash — it doesn’t affect your credit score.