IRD Penalties and Interest: How a Tax Debt Actually Grows
Owing Inland Revenue money feels like the debt is compounding away in the background at some punitive rate nobody will tell you. The reality is more specific and, for most people, considerably less alarming than the fear. There are two separate charges, they behave differently, and for the taxes most New Zealanders actually owe the penalty side stops growing after the first week. What keeps running is interest, and knowing which of the two you are dealing with changes what you should do about it.
The single fact that reframes this whole subject: the 1% monthly late payment penalty, the one that sounds like it will bury you, no longer applies to income tax, provisional tax or GST. Those are the three debts most people and most small businesses have. For them the penalties are a one-off hit in the first week, and after that the debt grows only at the interest rate.
The three things to remember
Penalties are charged for being late: 1% the day after the due date, then 4% on the seventh day. Interest is charged for the use of the money, currently 8.97% a year, calculated daily and not compounding. And the 1% monthly penalty does not apply to income tax, provisional tax or GST.
Not filing because you cannot pay. Filing and paying are separate obligations with separate penalties. If you file on time and simply cannot pay, you face the payment penalties only. If you also fail to file, you add a late filing penalty on top and you lose the ability to sort out an arrangement, because Inland Revenue cannot arrange a debt it has not yet assessed. Always file, even when the money is not there.
Two charges, not one
Almost every confusion about tax debt comes from treating penalties and interest as a single thing. They are separate, they are calculated differently, and they answer different questions.
A penalty is a charge for breaking a rule. It is a fixed percentage or a fixed dollar amount, applied once when the trigger happens. Use of money interest, which everyone shortens to UOMI, is not a punishment at all. It is the price of holding money that belonged to the government, calculated daily for as long as you hold it. Inland Revenue pays it in the other direction too when they have held your money.
The practical consequence is that penalties are front-loaded and interest is ongoing. A debt paid off quickly is dominated by the penalties. A debt that sits for a year or more is dominated by the interest.
The late payment penalties
These apply when tax is not paid by its due date. There are two initial steps and, for some tax types only, an ongoing monthly step.
Because the 4% is charged on the balance after the 1% has been added, the combined initial penalty is slightly more than 5% of the original tax. On $5,000 of unpaid income tax it works out at $252.00 rather than $250.00, which is a small difference but the sort of thing that makes a bill not match a mental estimate.
The monthly penalty was removed for income tax, provisional tax, GST and Working for Families overpayments. It still applies to other obligations, PAYE and employer deductions among them, which is one reason employer arrears are treated more seriously than a personal income tax bill. If you are an employer holding deductions you have taken from staff wages, the clock behaves differently and the debt needs dealing with faster.
The late filing penalties
These are separate again, and they are flat dollar amounts rather than percentages. They apply for not filing a return, regardless of whether you owed anything on it.
| Return | Penalty |
|---|---|
| Income tax return, net income under $100,000 | $50 |
| Income tax return, net income $100,000 to $1 million | $250 |
| Income tax return, net income over $1 million | $500 |
| GST return, payments basis | $50 |
| GST return, invoice or hybrid basis | $250 |
| Employment information | $250, charged monthly |
The income tax penalty starts at $50 and is adjusted once your actual net income is known from the return you eventually file. The employment information penalty is the one to watch, because unlike the others it repeats every month the information is outstanding, whatever your filing frequency.
Use of money interest
UOMI is the charge that keeps running. From 16 January 2026 the rate charged on underpaid tax is 8.97% a year, and the rate paid to you on overpaid tax is 2.25% a year.
Three features of how it is calculated matter more than the headline rate:
The gap between the two rates is worth noticing. Being 8.97% wrong in Inland Revenue's favour costs four times as much per dollar as being 2.25% wrong in your own, which is the practical argument for getting provisional tax estimates roughly right rather than deliberately overpaying as a safety measure. Overpaying is not free, it simply costs you the return you could have earned elsewhere.
A worked example
Take $5,000 of income tax, unpaid, and left for a full year.
That is a real cost and not one to shrug at. But it is also a knowable, straight-line cost, and it is less than most credit cards would charge on the same balance. If the only way to clear a tax bill immediately is to put it on a credit card, the arithmetic often says do not. Compare the two properly with the compound interest calculator before moving a debt from a simple-interest lender to a compounding one.
To run the figures on your own debt rather than this example, the IRD penalties and interest calculator applies the steps above to an amount and a period you enter.
What to do if you cannot pay
The order of operations matters, and it is not the order most people follow.
An instalment arrangement does not switch the interest off. UOMI continues on the outstanding balance for as long as it is outstanding, which is why paying more than the minimum still helps even once an arrangement is in place. What an arrangement does is stop the situation escalating and keep you out of the enforcement track.
Relief that genuinely exists
Inland Revenue has discretion to remit penalties and interest in defined circumstances. The clearest is where the failure was caused by an event outside your control, and there is a specific category for that. There is also relief where a penalty arose despite a genuine effort to comply, and separate provisions for serious hardship, which can extend to writing off part of a debt where recovering it would cause real financial distress.
None of this is automatic. It has to be asked for, in writing, with the circumstances explained. The two mistakes are assuming relief is impossible and therefore never asking, or assuming it is a formality and therefore not making a proper case.
Most tax debt starts as a provisional tax estimate that turned out to be wrong. The provisional tax calculator and the provisional tax method calculator show what the different methods produce, and the provisional tax guide explains which method suits which kind of income. Getting the method right prevents more penalty exposure than any amount of careful payment afterwards.
What this guide does not cover
There is a separate and much more serious category of penalty for getting a tax position wrong rather than merely being late: shortfall penalties, which run from a lack of reasonable care through to evasion and are charged as a percentage of the shortfall. Those are a different subject with different consequences, and anything involving one is worth taking to an accountant. This guide is about lateness, not accuracy. It is general information rather than tax advice.
Test Your Knowledge
Ten questions on how an Inland Revenue debt actually grows.
Sources: Inland Revenue on late payment penalties, late filing penalties, and interest on overpayments and underpayments. Interest rates effective 16 January 2026. Penalty and interest rates are set by legislation and Order in Council and change over time; check the current figures with Inland Revenue before relying on them.
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