PIE vs RWT NZ (2026): Why Your KiwiSaver Is Taxed Differently to a Bank Term Deposit

Your KiwiSaver PIE income is capped at a 28% PIR, but term deposit interest can be taxed at 39% RWT. Here is the after-tax comparison that surprises top earners.

Two New Zealanders can earn the exact same percentage return on their money in the same year and keep very different amounts after tax. The difference often comes down to a single technical point: whether the money sits inside a portfolio investment entity (PIE) or earns ordinary interest taxed under resident withholding tax (RWT). Your KiwiSaver is a PIE; a bank term deposit is not.

This guide explains the difference between the two tax systems, why your KiwiSaver income is capped at a 28% rate while term deposit interest is not, and what that means when you weigh a fund against a term deposit at the same headline rate.

TL;DR: KiwiSaver and other PIEs are taxed at your prescribed investor rate (PIR), which is capped at 28%. Bank interest is taxed under RWT at your marginal rate — up to 39% for income over $180,000. On a 5% gross return, a top earner keeps about 3.60% in a PIE versus 3.05% on a term deposit: roughly 55 basis points, purely from the cap. ¹³⁶

What's the difference between PIE tax and RWT?

Both are ways of taxing investment income, but they run on separate rules.

A PIE (portfolio investment entity) is a fund structure used by nearly every KiwiSaver scheme, most retail managed funds, and some specialist "cash PIE" savings accounts. The fund works out the income attributed to you and taxes it at your prescribed investor rate (PIR) — a flat rate of 10.5%, 17.5% or a maximum of 28%. ¹² That PIE tax is the final tax on the income; you do not add it to a tax return.

RWT (resident withholding tax) is the tax a bank deducts from interest before it reaches your account — on a term deposit, a savings account or a call account. You elect an RWT rate that matches your marginal income tax rate, and the interest is part of your taxable income. ³

The two systems are explained in more depth in our guide to how PIE tax works on your KiwiSaver. The key structural difference is the ceiling: a PIR stops at 28%, while RWT follows the full income tax scale.

Why is my KiwiSaver capped at 28% but my term deposit isn't?

The PIR scale was deliberately designed to top out at 28% — the company tax rate — rather than follow personal income tax all the way to 39%. ¹ So the highest rate any individual investor can be put on inside a PIE is 28%, even if their salary is taxed at 33% or 39%.

RWT was built the other way around. Because bank interest is treated as part of your ordinary taxable income, the available RWT rates mirror the personal tax brackets: 10.5%, 17.5%, 30%, 33% and 39%. ³ Someone whose total income exceeds $180,000 can elect 39% RWT, well above the 28% PIE ceiling. ³⁵

That gap is the whole story. For a dollar of return, a higher earner keeps more inside a PIE than on a term deposit, simply because the PIE tax stops climbing at 28% while RWT does not.

How RWT applies to bank interest and savings accounts

When you open an interest-bearing account, the bank asks for your IRD number and your chosen RWT rate. A few points are worth knowing:

• You choose the rate to match your income. The options are 10.5%, 17.5%, 30%, 33% or 39%, aligned to the personal tax brackets. ³
• If you choose nothing, the default is 33%. Banks apply a default RWT rate of 33% when you have not elected one. ⁴
• No IRD number means 45%. If the bank does not hold your IRD number, the non-declaration rate of 45% applies until you provide it. ⁴
• The interest is part of your taxable income. Unlike PIE income, term deposit interest is included in your income for the year, which can also affect things tested on total income.

The RWT thresholds follow the personal tax brackets for the 2025/26 year: 10.5% on income to $15,600, 17.5% to $53,500, 30% to $78,100, 33% to $180,000, and 39% above $180,000. ⁵ Choosing an RWT rate below your real marginal rate does not avoid the tax — it usually just leaves a bill to square up later.

Worked comparison: top earner in a PIE fund vs a term deposit

Take someone whose income puts them in the top bracket, so their RWT rate on interest is 39% and their PIR is the maximum 28%. Assume the same 5.00% gross annual return in both places — a term deposit paying 5.00%, and a cash PIE returning 5.00% before tax.

Illustrative calculation using current IRD PIR and RWT rates, 15 April 2026. Returns are not guaranteed and are shown to compare tax treatment only; actual rates and results will differ. ⁶

The 0.55 percentage-point gap is not the fund doing anything clever — it is purely the 28% cap versus 39% RWT on the same return. On larger balances that difference compounds, which is part of why the after-tax figure matters more than the headline rate. We walk through the full gross-to-net picture in what you actually keep after fees and tax.

A fair word of caution: this compares tax only. A term deposit's rate is contractually fixed for the term and the capital does not move; a cash PIE's rate can change and a non-cash fund's value can rise or fall. The tax comparison is like-for-like only when the gross returns are genuinely the same, which they often are not.

When does a PIE (including cash PIE) beat a standard term deposit?

On tax alone, a PIE comes out ahead once your marginal rate is above 28% — that is, when you are in the 30%, 33% or 39% bracket. ⁷⁸ At those rates the 28% cap saves you tax on every dollar of return compared with the same money earning interest taxed at your full marginal rate.

This is why some banks and providers offer "cash PIE" accounts alongside ordinary term deposits and savings accounts. For a higher earner, a cash PIE returning the same gross rate as a term deposit leaves more after tax, because the income is capped at 28% rather than taxed at 30%, 33% or 39%. BNZ and IRD guidance both note that you benefit from a PIE if you pay tax at 30%, 33% or 39%, precisely because the highest PIR is 28%. ⁸

Two caveats keep this honest:

• It only helps above 28%. If your marginal rate is 28% or below, there is no cap advantage (more on that next).
• Gross rates have to match. A cash PIE only wins if it pays a comparable gross rate. Always compare the actual rate on offer, not just the tax label.

What about lower earners — does the cap still help?

For most people on lower incomes, the cap gives no benefit, because their PIR already equals their marginal rate. ⁷

• Someone correctly on the 17.5% PIR pays 17.5% inside a PIE and can elect 17.5% RWT on interest — same rate either way.
• Someone on 10.5% pays 10.5% in both. ⁷

So the PIE only wins on tax once the marginal rate climbs past 28%. For lower earners the more important issue is a different one: making sure you are actually on your correct, lower PIR rather than being defaulted to 28%. If a provider does not hold your IRD number, or you never set a PIR, you can sit on the top 28% rate for years while genuinely qualifying for 17.5% — and quietly overpay. Our guide on what PIR you should be on walks through the two-year income test.

For lower earners weighing a cash PIE against a term deposit, the decision usually comes down to the gross rate, access to the money and certainty — not the tax treatment, because the tax is much the same.

Choosing between a cash PIE and a term deposit

The tax cap is one input, not the whole decision. A few factors usually matter more:

For a top-bracket earner holding cash for the medium term, the 28% cap is a real, automatic advantage when gross rates are comparable. For a lower earner, the two are close to neutral on tax, so the rate and access terms should drive the choice. And none of this turns a cash product into a growth investment — a cash PIE and a term deposit are both low-return, capital-stable options, not a substitute for a diversified KiwiSaver fund over a long horizon.

Frequently asked questions

Is KiwiSaver taxed differently to a term deposit? Yes. KiwiSaver is a PIE, so its income is taxed at your prescribed investor rate (PIR), capped at 28%. A term deposit's interest is taxed under RWT at your marginal rate, which can reach 39% for income over $180,000. ¹³

What is the maximum PIE tax rate in New Zealand? The highest PIR for an individual investor is 28%, which is also the default if you have not set a rate or your provider does not hold your IRD number. ¹²

What RWT rate should I be on for a term deposit? You elect an RWT rate matching your marginal income tax rate — 10.5%, 17.5%, 30%, 33% or 39%. If you elect nothing the default is 33%, and with no IRD number on file the bank applies 45%. ³⁴

Does a cash PIE always beat a term deposit? No. A cash PIE only has a tax advantage when your marginal rate is above 28% — the 30%, 33% or 39% brackets — and only when it pays a comparable gross rate. For lower earners the tax is much the same, so the rate and access terms matter more. ⁷⁸

How much does the 28% cap actually save a top earner? On a 5.00% gross return, a 39% RWT investor keeps about 3.05% after tax, while the same return in a PIE at the 28% cap keeps about 3.60% — roughly 0.55 percentage points, purely from the cap. Actual results depend on the rates on offer. ⁶

Does PIE income affect my tax return? No. PIE income is taxed as a final tax through your provider, so it does not go in a tax return. Term deposit interest is part of your taxable income. ¹³

General information, not personalised financial advice. It does not take into account your particular financial situation, goals or needs. Seek advice tailored to your circumstances before acting. KiwiSaver tax (PIR) and RWT settings are set by the Government and can change; figures are correct as at 15 April 2026 — check current rules at ird.govt.nz. 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). Written by Henry Smith, Financial Adviser; reviewed by Craig Smith, Principal Adviser. Last reviewed 15 April 2026.