Provisional tax is one of those topics that confuses a lot of self-employed people and small business owners in New Zealand. If you have ever received a provisional tax bill from Inland Revenue and wondered what it was or how it was calculated, you are not alone.
In this guide, we will explain what provisional tax is, who needs to pay it, the three methods available for calculating it, and the due dates you need to know.
What Is Provisional Tax?
Provisional tax is not a separate tax. It is simply a way of paying your income tax in instalments throughout the year, rather than in one lump sum after the end of the tax year. It applies to people whose income is not fully covered by PAYE — typically the self-employed, contractors, landlords, and investors.
If your residual income tax (RIT) for the previous year was more than $5,000, you are a provisional taxpayer. Residual income tax is the tax you owe at the end of the year after subtracting any PAYE, withholding tax, and tax credits already paid.
The purpose of provisional tax is to spread the payment across the year so you do not face a large tax bill all at once, and so IRD receives revenue more evenly throughout the year.
The Three Methods for Calculating Provisional Tax
You can choose from three methods for working out how much provisional tax to pay:
1. Standard Method (Uplift)
This is the default method and the one IRD will use if you do not choose another option. Under the standard method, your provisional tax for the current year is calculated as your residual income tax from the previous year, plus 5% (the uplift). This total is then divided into three equal instalments.
For example, if your residual income tax last year was $10,000, your provisional tax for this year would be $10,500 ($10,000 + 5%), paid in three instalments of $3,500 each.
The advantage of the standard method is simplicity — you do not need to estimate your income. The disadvantage is that if your income drops significantly, you might be overpaying. If your income increases, you might underpay and face use-of-money interest.
2. Estimation Method
With the estimation method, you estimate your total income tax for the current year and pay provisional tax based on that estimate. This can be useful if you expect your income to be significantly different from last year — either higher or lower.
The advantage is flexibility — you pay based on what you actually expect to earn, not what you earned last year. The risk is that if you underestimate your income, you will be exposed to use-of-money interest (UOMI) on the shortfall from the original due dates. If you overestimate, you simply get a refund.
If you use the estimation method, you need to file an estimate with IRD. You can revise your estimate during the year if your circumstances change.
3. Accounting Income Method (AIM)
The AIM method is the newest option and is designed for businesses that use accounting software. Under AIM, your provisional tax is calculated automatically each period (usually two-monthly) based on your actual accounting data. Your accounting software works out the tax due and files the information with IRD.
AIM is only available to businesses with annual turnover under $5 million and requires compatible accounting software (such as Xero, MYOB, or other approved software). The main advantage is accuracy — you pay tax based on actual results, so you should not have significant over- or under-payments. The main disadvantage is that it requires up-to-date accounting records, which not all businesses maintain.
A key benefit of AIM is that you are not exposed to use-of-money interest, as long as you use the method correctly and file on time.
Provisional Tax Due Dates
The due dates for provisional tax depend on your balance date (the end of your tax year) and which method you use. For most people with a standard 31 March balance date:
Standard and Estimation methods (three instalments):
- Instalment 1: 28 August
- Instalment 2: 15 January
- Instalment 3: 7 May
AIM method (six instalments, two-monthly):
- 28 July, 28 September, 28 November, 28 January, 28 March, 28 May
If a due date falls on a weekend or public holiday, the payment is due on the next working day.
Use-of-Money Interest (UOMI)
If you underpay your provisional tax (because your income was higher than expected or you underestimated), IRD charges use-of-money interest on the shortfall. The UOMI rate for underpayments is typically around 7-8% per annum, which is significant.
Conversely, if you overpay, IRD pays you interest on the excess — but at a much lower rate (typically around 1-2%). This asymmetry means it is generally better to slightly overpay than to underpay.
If you use the standard method and pay on time, you are generally protected from UOMI on the first two instalments, even if the total ends up being insufficient. The exposure is mainly on the third instalment and the period between the third instalment and the final assessment.
If you use AIM and file correctly, you are not charged UOMI at all.
Tax Pooling
Tax pooling is a service offered by intermediaries that allows you to manage provisional tax payments more flexibly. You pay into a pool managed by the intermediary, and if you have underpaid, you can purchase tax from the pool at a date earlier than when you actually made the payment. This effectively backdates your payment and reduces or eliminates UOMI.
Tax pooling is particularly useful for businesses whose income is unpredictable. The intermediary's fee is usually much less than the UOMI you would otherwise pay.
What If You Cannot Pay?
If you know you cannot pay your provisional tax on time, contact IRD before the due date. They can often arrange an instalment plan, which avoids late payment penalties (though interest may still apply). Ignoring the bill is the worst option — penalties and interest accumulate quickly.
Provisional Tax and GST
If you are registered for GST, you can align your provisional tax payments with your GST return dates. This is called the ratio method and can simplify your compliance by combining provisional tax payments with your regular GST returns. You pay a percentage of your GST sales as provisional tax each period.
Tips for Managing Provisional Tax
- Set money aside regularly. Do not wait for the due dates. Transfer a portion of each invoice or payment you receive into a separate tax savings account.
- Keep your accounting up to date. If you use AIM, this is essential. Even if you do not, knowing your year-to-date position helps you estimate accurately.
- Review your method annually. If your income is stable, the standard method is easiest. If it fluctuates, estimation or AIM might save you money on interest.
- Use tax pooling if needed. If you have underpaid, tax pooling can be much cheaper than paying UOMI directly to IRD.
Final Thoughts
Provisional tax is simply a mechanism for paying your income tax in advance. The key is choosing the right method for your situation, paying on time, and keeping good records. If you are newly self-employed and this is your first year with residual income tax over $5,000, make sure you understand the system before the first instalment is due.
Use our New Zealand salary calculator to estimate your income tax position and plan your provisional tax payments accordingly.