If you overpay any tax or duty, we'll pay you back with interest. If you underpay tax, we'll charge you interest. We may also charge a penalty with interest. This is often called use of money interest, or UOMI.
What interest is applied to
Interest applies to these taxes, duties and revenue types:
- casino duty
- child support deductions by employers (CSE)
- FamilyBoost (FMB)
- fringe benefit tax (FBT)
- gaming machine duty and problem gambling levy
- goods and services tax (GST)
- imputation accounts
- income tax
- KiwiSaver contributions
- lottery duty
- non resident withholding tax (on interest and dividends)
- PAYE deductions
- residential land withholding tax (RLWT)
- resident withholding tax (RWT) (on interest and dividends)
- student loan deductions by employers
- ESCT (employer superannuation contribution tax)
- totalisator duty (betting levy)
- Working for Families Tax Credits (WfFTC).
We do not apply interest for:
- amounts under $100
- child support payments.
We do not apply credit interest for FamilyBoost.
Student loans may have interest applied.
Student loan interest and fees
Interest amounts
Interest gets calculated daily on your overpaid or underpaid tax. It does not compound and is not included when calculating penalties.
The interest rates are set by government and are based on market rates, so they vary over time.
| When interest rate started | Debit rate | Credit rate |
|---|---|---|
| 8 May 2025 | 9.89% | 3.27% |
| 16 January 2025 | 10.88% | 4.30% |
| 29 August 2023 | 10.91% | 4.67% |
| 9 May 2023 | 10.39% | 3.53% |
| 17 January 2023 | 9.21% | 2.31% |
| 30 August 2022 | 7.96% | 1.22% |
| 10 May 2022 | 7.28% | 0.00% |
| 8 May 2020 | 7.00% | 0.00% |
| 29 August 2019 | 8.35% | 0.81% |
| 8 May 2017 | 8.22% | 1.02% |
| 8 May 2016 | 8.27% | 1.62% |
| 8 May 2015 | 9.21% | 2.63% |
When interest starts
If you've underpaid tax or duty, interest:
- starts on the day after the original due date for the amount owing, or
- starts from a new due date (if you received Working for Families Tax Credit and you meet specific criteria to have a new due date)
- stops on the day the overdue balance (including interest) gets paid in full.
If you've overpaid tax or duty, interest starts on the latest of either:
- the day after the original due date
- the day after payment.
If you need to file a tax return to get a refund of your overpayment, interest starts on the latest of the:
- original due date
- day after the payment that generates the refund (that's when the credit becomes available)
- date you filed your return.
In most cases, interest stops the day the overpaid tax is refunded or transferred to another tax account or period.
Interest you're paid is gross income
Any interest you're paid on an overpayment is gross income. You'll need to include it in your income tax return or income tax assessment for the year in which it's refunded. You need to do this even if you credit the interest towards paying other unpaid tax.
If your return is reassessed and we find that you've overpaid, you may be paid interest. This is also gross income but only in the income year following the year of assessment.
Underpaid interest is deductible
Interest you pay on underpayments of tax is deductible for business purposes. You can claim it as an expense on your income tax return.
If your return is reassessed and we find that you've underpaid, you may have to pay interest. This is also deductible, but only in the income year following the year of reassessment.
Interest on tax in dispute
When you're disputing a tax amount, you can put payment on hold until a decision is made. If we decide the amount in dispute is not right, we'll refund the disputed tax and pay you interest on it. If we decide that the amount in dispute is right, you'll have to pay us any outstanding amount and any interest on it.
Interest and extra time to pay
When you get a notice of assessment or a statement of account balance we'll give you up to an extra 30 days to pay. If you pay the balance within that timeframe, you do not need to pay the interest that gets added between the date the notice or statement was issued, and the date of the payment.
If you pay after more than 30 days, the interest amount will be recalculated, so the balance may not be cleared in full.
Interest and payments
If you make a payment to clear unpaid tax, it is used to pay off unpaid interest and then tax. The exception to this rule is for payments of provisional tax, where payments are used for provisional tax instalments as directed by the taxpayer.
Credit interest may be used to pay other unpaid taxes.
GST and provisional tax
There are different rules about interest on GST and provisional tax.