PIR Too Low? How an Under-Set KiwiSaver Tax Rate Leaves You With an IRD Bill (NZ, 2026)

An under-set KiwiSaver PIR does not save you tax — it defers it. Here is how the year-end shortfall is calculated, who is most at risk, what the 28% cap does and does not protect, and how to fix your rate.

TL;DR: If your KiwiSaver PIR (Prescribed Investor Rate — the tax rate on your KiwiSaver earnings) is set lower than it should be, you do not avoid the tax. Inland Revenue works out the shortfall at year-end and adds it to your tax to pay ⁵. On 10.5% when you should be on 28%, that is a $175 shortfall for every $1,000 of KiwiSaver income ¹.

A PIR that is too low can feel like a win — less tax taken from your fund through the year, a balance that looks like it is growing a little faster. It is not a win. Since the rules changed for the 2021 tax year, Inland Revenue squares up the difference each year and asks you to pay it ⁷⁸. The money was always owed; an under-set rate just delays the moment you part with it, and lands the bill as cash you have to find at year-end rather than tax quietly settled inside the fund.

This guide explains how that shortfall is calculated, why the 28% cap does not rescue a top earner, roughly how much it can come to, whether penalties apply, and how to set the rate right.

What does it mean if my KiwiSaver PIR is too low?

Your KiwiSaver fund is almost always a Portfolio Investment Entity, or PIE. Instead of taxing the fund at a flat company rate, a PIE taxes the income attributed to you at your personal PIR. There are three rates for New Zealand resident individuals — 10.5%, 17.5% and 28% — and you cannot choose 0% ¹. Which one is correct for you is fixed by your income, not by preference.

Your correct PIR is based on your taxable income (and taxable income plus PIE income) across the last two income years, and you use whichever of those two years gives the lower rate ³. So the rate genuinely can sit below your current salary band for a legitimate reason. A PIR is "too low" only when it is below the rate that test actually produces — for example, sitting on 17.5% when both look-back years put you firmly in the 28% band.

This happens more often than people expect. Someone sets 10.5% as a student, then moves into a well-paid role and never updates it. A contractor's income climbs across two good years but the rate set at the start stays put. Because correctly-rated PIE income normally stays off your tax return, there is no obvious annual nudge telling you the rate has drifted out of date.

How does a low PIR create a tax bill at year-end?

For most of KiwiSaver's history, PIE tax was final — whatever rate came out was the end of it. That changed. From the 2020-21 income year onward, Inland Revenue performs a year-end calculation of any PIE tax under- or over-paid ⁸.

Here is the sequence for an under-set rate:

• Through the year, your provider deducts PIE tax at the rate you gave them.
• After 31 March, IRD compares the tax actually deducted against the tax due at your correct PIR for the year ⁵.
• If you used a rate that was too low, the outstanding PIE tax liability is calculated and included in your tax to pay as part of your income tax assessment ⁵.
• You then have to find the cash to settle that shortfall — it does not come back out of the fund automatically.

That is the key shift. An under-set PIR no longer quietly saves you anything; it converts a small, invisible deduction inside your fund into a visible bill you settle from your bank account ⁵⁸. For the mirror image — a PIR set too high — IRD issues a credit and refunds the overpayment instead ⁷. Our companion guide on overpaying KiwiSaver tax with a too-high PIR covers that side.

Why doesn't the 28% cap protect me if I'm a 39% earner?

This is the part that catches high earners out. The top PIR is 28%, which sits below the top personal marginal income tax rate of 39% (on income over $180,000) ⁴. So even on the correct top rate, a high earner pays PIE tax well under their marginal rate — that gap is a deliberate feature of the PIE regime, not a loophole ⁴.

The cap, though, only helps you once you are on the correct rate. It does not let you sit below it for free. Before the 2021 reform, an under-set PIR could push your PIE income all the way up to your full 33% or 39% marginal rate at year-end. The reform removed that sting: the 28% cap still applies to the PIE income, so you are not dragged up to 39% ⁷. But you must still pay the shortfall between the rate actually deducted and 28% ⁷.

So a 39% earner sitting on, say, 17.5% does not escape with a 17.5% bill, and is not punished with a 39% one. They owe the gap up to 28% — the 10.5 percentage points between 17.5% and the cap — on every dollar of PIE income for the year. The cap limits how bad the bill gets; it does not make the bill disappear.

How much could an incorrect PIR cost me?

The shortfall is simply the difference between the rate you used and the rate you should have used, applied to your attributed PIE income for the year — never more than the 28% cap ¹⁷. The table below shows the gap per $1,000 of PIE income for the common under-set combinations.

Figure — Tax bill from an under-set PIR by income band

Source: IRD PIR rates 10.5% / 17.5% / 28% ¹; shortfall capped at 28% ⁷. The bill rises with your attributed PIE income.

Scale it to a balance. PIE income is the income your fund attributes to you in a year, not your whole balance — but on a six-figure balance in a reasonable year it can run to a few thousand dollars. On $3,000 of attributed PIE income, a 28% earner sitting on 10.5% faces a shortfall of 17.5% × $3,000 = $525 for that single year ¹. On 17.5% when 28% was correct, the gap on the same $3,000 is 10.5% × $3,000 = $315 ¹⁷.

These figures are illustrations using the current PIR rates, not predictions; your actual attributed PIE income and correct rate will differ. A wrong rate left running across several years simply repeats the shortfall each year — and each one is a fresh bill, not a one-off.

Will IRD charge penalties or interest on under-paid PIE tax?

The under-paid PIE tax is folded into your year-end income tax assessment as tax to pay ⁵. How that bill behaves then follows Inland Revenue's normal rules for tax owing at year-end rather than anything PIE-specific.

A point worth knowing for higher earners: if your residual income tax for the year tips over a set threshold, you can be drawn into provisional tax for following years, which changes when and how you pay. That is a high-income consideration, not a part-timer's. Because penalty, interest and provisional-tax settings depend on your full circumstances and can change, this is general information only — the cleaner course is to stop the shortfall accruing by setting the right rate, and to confirm the specifics with Inland Revenue or your accountant. Smiths Financial does not provide tax structuring or accounting advice; please consult an appropriately authorised professional for your tax position.

The practical takeaway: an under-set PIR is not a way to defer tax cheaply. At best you pay the same tax later as a lump sum; at worst the timing pulls you into extra obligations. There is no upside to leaving it low.

How do I update my PIR with my KiwiSaver provider?

You change your PIR by telling your KiwiSaver or PIE provider directly — not Inland Revenue ⁸. Most providers let you do it in their app or online portal in a few minutes. IRD may also notify your provider of the correct rate, and it runs the year-end wash-up regardless ⁸, but you should not wait for that to fix the rate going forward.

Provider portal paths change; confirm the current step with your provider. List is not exhaustive — every scheme accepts a PIR update through its app, website or support line.

Two things to check while you are there. First, your IRD number must be on file, or the provider applies the default 28% regardless ¹ — which for a genuine 28% earner is at least the right rate, but for a lower earner means overpaying. Second, joint accounts generally apply the higher holder's PIR, so check those separately.

If you are not certain which band your last two income years put you in once you net off a part-year salary, study income or a contracting year, our guide on what PIR you should be on walks through the thresholds, and a KiwiSaver review will read it off your statements with you.

How do bonuses, pay rises and side income change my correct PIR?

A PIR is correct for the income it was set against; it does not adjust itself when your income climbs. Anything that lifts your taxable income across the look-back years can push your correct rate up a band, while your set rate stays where it was.

• A pay rise that carries your taxable income over $53,500 across both look-back years can move your correct rate from 17.5% to 28%.
• A bonus adds to taxable income for that year and can tip a borderline year into a higher band.
• Side or contracting income stacks on top of your salary in the same taxable-income figure — easy to overlook because it is not on your main payslip.
• Investment growth itself can matter, because the second test is taxable income plus PIE income; a strong year can lift the combined figure over $78,100.

Because the rate uses the lower of your last two income years ³, a single big year does not always move you straight away — but two strong years in a row will. Our note on how a pay rise or bonus changes your KiwiSaver PIR covers the timing in more detail. The simplest habit is to check your PIR once a year, and again after any meaningful change in income.

Frequently asked questions

What does "PIR too low" actually cost me? The shortfall is the gap between the rate you used and your correct rate, applied to your attributed PIE income, capped at 28% ¹⁷. On 10.5% when 28% is correct, that is $175 per $1,000 of PIE income; on 17.5% when 28% is correct, $105 per $1,000 ¹. IRD adds the total to your year-end tax to pay ⁵.

Doesn't the 28% cap mean I can't owe much? The cap limits how high the bill goes — you are not dragged up to your full 39% marginal rate as you were before the 2021 reform ⁷. But you still owe the shortfall up to 28% ⁷. The cap is a ceiling on the bill, not a way to avoid it.

Will I get penalties or interest on the under-paid PIE tax? The shortfall is included in your income tax assessment as tax to pay ⁵, and then follows IRD's normal rules for tax owing, which depend on your wider circumstances. This is general information only — check the specifics with Inland Revenue or your accountant.

How do I fix a PIR that is too low? Tell your KiwiSaver or PIE provider your correct rate directly — not IRD ⁸. Most allow the change in their app or portal in a few minutes. IRD also runs a year-end wash-up, but updating with your provider is what stops the shortfall accruing going forward ⁸.

My income went up this year — has my PIR changed automatically? No. Your provider keeps using the rate you gave until you change it. Your correct PIR is based on the last two income years, using the lower-rate year ³, so a single higher year may not move you immediately — but it is worth re-checking after any pay rise, bonus or new side income.

Is a too-low PIR a way to defer tax? Not usefully. The tax was always owed; an under-set rate just shifts it from a quiet in-fund deduction to a lump sum you pay at year-end ⁵⁸, and for higher earners the timing can create further obligations. There is no genuine saving in leaving it low.

This article is general information only and is not personalised financial advice. It does not take into account your particular financial situation, goals or needs. Before acting, consider whether it's right for you and seek advice tailored to your circumstances. Craig Smith Business Services Ltd (FSP712931), trading as Smiths Financial, holds a Class 2 licence issued by the Financial Markets Authority and is a member of the Financial Dispute Resolution Service (FDRS). KiwiSaver is a long-term savings scheme; tax (PIR) settings are set by the Government and can change — figures are correct as at 17 May 2025, so check current rules at ird.govt.nz. Written by Henry Smith, Financial Adviser; reviewed by Craig Smith, Principal Adviser. Last reviewed 17 May 2025.