IRD Interest & Penalty Calculator

Inland Revenue charges use-of-money interest (UOMI) on tax that is paid late or underpaid. As of 2025, the IRD underpayment interest rate is approximately 10.9% per annum. This rate is set quarterly by the Commissioner of Inland Revenue under a formula linked to the 90-day bank bill rate, plus a margin. UOMI applies to underpaid provisional tax (from each instalment date), terminal tax (from the due date, typically 7 April for standard balance date taxpayers), unpaid GST, and other unpaid tax obligations. Importantly, UOMI is tax-deductible for income tax purposes — so if you are in a 33% tax bracket, the after-tax cost of UOMI is approximately 7.3%. Conversely, IRD also pays interest (the overpayment rate) on tax overpayments, which was approximately 2.31% per annum in 2025. UOMI is not a penalty — penalties apply separately for not filing or for tax shortfalls. Source: IRD — Use-of-Money Interest (ird.govt.nz/income-tax/provisional-tax/use-of-money-interest).

Use-of-money interest (UOMI) in New Zealand is calculated on a daily compounding basis. The formula is: daily interest = outstanding tax amount * (annual rate / 365). This amount is added to the balance each day, and interest is then charged on the growing balance (compound interest). For example, $10,000 of unpaid tax at 10.9% per annum accrues approximately $2.99 per day in interest in the first day. Over 90 days, the total UOMI would be approximately $272. UOMI starts accruing from the date the tax was due (the instalment date for provisional tax, or the terminal tax date) and stops when the outstanding tax is paid in full. UOMI applies to the core tax amount — if you also have late payment penalties, those are calculated separately and do not attract additional UOMI. IRD's online tax accounts and calculators show the current UOMI balance. Source: IRD — UOMI Calculation (ird.govt.nz/income-tax/provisional-tax/use-of-money-interest).

There are several strategies to avoid use-of-money interest (UOMI) on provisional tax in New Zealand. The safe harbour rule is the most straightforward: if your prior-year residual income tax (RIT) was under $60,000 and you pay all three standard uplift instalments on time and in full, you are protected from UOMI even if you end up owing more terminal tax. This works because the standard uplift (105% of prior-year RIT) may understate your actual tax if your income has grown. Tax pooling is another effective strategy: IRD-approved tax pooling intermediaries (such as Tax Traders or Flexitax) allow you to buy provisional tax credits from other taxpayers who overpaid, at a cost typically well below the UOMI rate. Tax pooling credits can even be purchased retrospectively after the provisional tax date. Using the estimation method accurately is also an option, but requires reliable forecasting of your income to avoid underpaying. Source: IRD — Avoiding UOMI (ird.govt.nz/income-tax/provisional-tax/use-of-money-interest).

Tax pooling is an IRD-approved mechanism that allows New Zealand taxpayers to buy and sell provisional tax credits through a licensed intermediary. Here is how it works: some taxpayers overpay their provisional tax during the year; these overpayments sit in a pooled tax account held with IRD; taxpayers who have underpaid can then purchase these surplus credits, effectively transferring the overpayment to offset their own shortfall. The key benefit is cost savings: buying tax pooling credits typically costs significantly less than the UOMI rate IRD charges (around 10.9% p.a.). The effective rate through pooling intermediaries is often in the range of 6-8% p.a. Additionally, credits can be purchased retrospectively — even after a provisional tax instalment date has passed — which provides flexibility to manage unexpected income or shortfalls. Tax pooling is governed by sections RP 17 to RP 19 of the Income Tax Act 2007. IRD-approved intermediaries include Tax Traders, Flexitax, and TMNZ (Tax Management NZ). Source: IRD — Tax Pooling (ird.govt.nz/income-tax/provisional-tax/use-of-money-interest).