Negative Real Rate of Return on Term Deposits

Is your term deposit actually going backwards? A 4% return sounds reasonable. With the Official Cash Rate sitting at 2.25% and banks advertising competitive rates, you could be forgiven for thinking your savings are earning their keep.

They're not. Once you account for inflation and tax, most New Zealand term deposits are delivering what's known as a negative real rate of return. Your money is quietly losing purchasing power while sitting in what feels like the safest place on earth.

This article explains exactly how the maths works, using current New Zealand data, so you can see for yourself what a term deposit actually costs you in real terms.

What Is a Real Rate of Return?

The real rate of return is the return on an investment after adjusting for inflation. It tells you whether your money is growing in terms of actual purchasing power, or just growing in nominal terms while the cost of living rises around it.

Banks advertise nominal interest rates. A 4% term deposit means you'll receive 4% in interest over the year. But if the prices of goods and services rise by 3% in the same period, your real gain is much smaller than it appears. And once tax enters the picture, even a modest inflation rate can push the real return into negative territory.

How Inflation Erodes Your Savings

Inflation measures the rate at which average prices rise across the economy. The Reserve Bank of New Zealand (RBNZ) describes it as the "thief in your wallet," and targets an annual rate between 1% and 3%, with a focus on the 2% midpoint.

One important caveat: the Consumer Price Index (CPI) published by Stats NZ is an average across a broad basket of goods and services. Your personal rate of inflation may differ significantly, particularly if a large share of your spending goes toward essentials such as electricity, council rates, insurance, and groceries, all of which have been rising faster than the headline figure.

As at the December 2025 quarter, New Zealand's annual CPI inflation was running at 3.1%, just above the top of the RBNZ's target band. Electricity prices rose 12.2% over the year. Council rates increased 8.8%. Rents climbed 1.9%. For households skewed toward these categories, the effective rate of inflation is likely well above 3.1%.

Even when inflation sits at a modest 2%, it halves the purchasing power of your money over roughly 35 years. At 3%, it takes just 23 years. The RBNZ's own inflation calculator shows how dramatically a dollar's value declines over time.

The Tax Bite: RWT on Nominal Returns

Here is where the maths turns uncomfortable. In New Zealand, Resident Withholding Tax (RWT) is charged on the full nominal interest you earn, not on your real (inflation-adjusted) return. The tax system does not distinguish between genuine gains and the portion of your interest simply compensating for lost purchasing power. You are taxed on every dollar of interest as if it were a real gain.

Your RWT rate should match your marginal income tax rate. For the 2025/26 tax year, the personal income tax rates set by the Inland Revenue Department (IRD) are:

• 10.5% on income up to $15,600
• 17.5% on income from $15,601 to $53,500
• 30% on income from $53,501 to $78,100
• 33% on income from $78,101 to $180,000
• 39% on income over $180,000

This creates an asymmetry worth understanding. You earn nominal interest. You are taxed on nominal interest. But you live in a world of real prices. The gap between the two is where your wealth quietly disappears.

This is not a uniquely New Zealand problem. Savers in Australia, the UK, and Canada face similar dynamics whenever after-tax deposit rates trail inflation. But New Zealand's comparatively high marginal tax rates on interest, with no tax-free threshold on the first dollar of income, make the effect particularly pronounced.

Worked Example: What $100,000 Actually Earns You

Consider a $100,000 term deposit at 4.00%, which as of early 2026 is among the best 12-month rates available from a New Zealand bank.

You earn $4,000 in gross interest over the year.

If you're on the 33% marginal tax rate (income between $78,101 and $180,000), you pay $1,320 in RWT. Your after-tax return is $2,680, or 2.68%.

Inflation over the same period is 3.1%. So the real purchasing power of your $102,680 is equivalent to roughly $99,580 in today's dollars. You locked your money away for 12 months and came out with less buying power than you started with.

For someone in the 39% tax bracket (income above $180,000), the picture is worse. RWT takes $1,560, leaving $2,440 after tax, or 2.44%. Against 3.1% inflation, the real return is approximately negative 0.66%. On $100,000, your purchasing power has fallen by about $660 in a single year.

Even at the 30% rate (income between $53,501 and $78,100), the after-tax return of 2.80% still falls short of 3.1% inflation. At current rates, every tax bracket above 17.5% delivers a negative real return on a 4% term deposit.

A quick way to check your own position: take your term deposit rate, multiply it by (1 minus your tax rate), and compare the result to the latest annual CPI figure. If the after-tax number is lower, your savings are going backwards in real terms.

PIE Term Deposits: A Partial Fix

A Portfolio Investment Entity (PIE) term deposit is taxed at your Prescribed Investor Rate (PIR), which is capped at 28%. For anyone on a marginal tax rate of 30% or above, this cap provides a meaningful advantage over a standard term deposit taxed via RWT. You can check which PIR applies to you on the IRD website.

Using the same $100,000 at 4.00%, a PIE investor pays tax at 28%, keeping $2,880 after tax, or 2.88%. Against 3.1% inflation, the real return is still negative, at roughly minus 0.22%, but the loss is noticeably smaller than the minus 0.42% faced by a standard term deposit holder in the 33% bracket.

PIE structures are worth considering if you are in a higher tax bracket and committed to holding cash. Most major New Zealand banks offer PIE term deposits, though availability, terms, and minimum deposits vary. However, a PIE does not solve the fundamental problem: when inflation exceeds your after-tax return, your money is still losing ground.

The Decade Test

One year of negative real returns is easy to overlook. A decade of them is not.

Suppose you hold $100,000 in a standard term deposit earning 4.00% per year (reinvesting interest), and your marginal tax rate is 33%. Your after-tax compound return is 2.68% per year. After 10 years, your balance reaches approximately $130,400 in nominal terms. It feels like growth.

But if inflation averages 3.1% over the same period, the cumulative rise in prices is roughly 36%. In today's purchasing power, your $130,400 is worth approximately $96,000. You've gone backwards by about $4,000 in real terms, despite never touching the money and dutifully reinvesting every dollar of after-tax interest.

At the 39% tax rate, the same exercise produces a real balance of approximately $93,700 after a decade. A loss of more than $6,000 in purchasing power, from what most people consider the safest investment available.

These figures are illustrative. They assume a constant 4% nominal rate and 3.1% inflation, neither of which will hold precisely over a decade. Interest rates, tax brackets, and inflation all fluctuate. But the direction has been remarkably consistent across most post-2008 interest rate environments in New Zealand: after tax and after inflation, term deposits have rarely delivered a positive real return for anyone in a tax bracket above 17.5%.

The Depositor Compensation Scheme: Safe, but Not Growing

Since 1 July 2025, New Zealand's Depositor Compensation Scheme (DCS) protects eligible deposits up to $100,000 per depositor, per licensed deposit taker, in the event of institutional failure. This brought New Zealand into line with most other OECD nations after decades without any form of deposit insurance.

The DCS is an important development. It means your capital is genuinely safer than it has ever been in a New Zealand bank. For a detailed look at how the scheme works and what it covers, see our guide on whether your money is safe in a New Zealand bank.

What the DCS does not do is protect you from inflation. Your $100,000 is guaranteed in nominal terms, but its purchasing power is not. The scheme ensures you get your dollars back. It does not ensure those dollars buy what they bought when you deposited them.

If you're wondering whether your savings are structured to keep pace with the cost of living, a conversation with a qualified adviser can help clarify where you stand. Feel free to get in touch with the team at Become Wealth.

When Term Deposits Still Make Sense

Note: term deposits serve a clear purpose in specific situations:

• An emergency fund covering three to six months of living expenses belongs in a liquid, low-risk vehicle. A savings account or short-term deposit is appropriate here.
• Cash earmarked for a specific purchase within the next 12 to 24 months, such as a property deposit, a renovation, or a vehicle, should generally not be exposed to investment market volatility.
• Retirees drawing down capital may hold a portion in cash or short-term deposits to cover near-term spending, so they aren't forced to sell investment assets during a market downturn.

In each case, the term deposit serves as a holding bay for money with a short time horizon, not as a long-term wealth-building tool. The problem arises when term deposits become the default home for savings intended to fund goals years or decades away. Over those timeframes, negative real returns compound against you.

There is also a behavioural dimension worth acknowledging. Some investors value the certainty and simplicity of term deposits, even at the cost of real returns. If the alternative is money sitting in a cheque account earning nothing, a term deposit is clearly preferable. And for people who would otherwise lose sleep over short-term market movements, a lower real return may be a reasonable price to pay for peace of mind. The key is making the trade-off consciously, with the full picture in view.

What Are the Alternatives?

The question is whether your overall mix of assets gives you a reasonable prospect of growing wealth in real terms over time.

A well-diversified investment portfolio across multiple asset classes, including shares, bonds, property, and cash, has historically delivered returns above inflation over medium-to-long timeframes. The trade-off is accepting short-term volatility in exchange for long-term real growth. Depending on your risk tolerance and time horizon, the spectrum ranges from conservative funds with a heavier weighting toward bonds and cash, through to growth-oriented funds with greater exposure to shares and property. Managed funds, including those offered through KiwiSaver Schemes, provide access to these options at various risk levels.

For those planning for retirement or reviewing their overall financial plan, understanding the real return on every component of your wealth is a sensible starting point. It is often the part of the conversation clients find most revealing.

Negative Real Rate of Return on Term Deposits

A negative real rate of return may be the new normal.

In most post-2008 interest rate environments, New Zealand term deposits have struggled to deliver positive real returns for savers in tax brackets above 17.5%. The combination of RWT on nominal interest and persistent inflation means the real return on cash is almost always lower than it appears, and frequently negative.

Term deposits remain valuable for short-term liquidity, capital preservation over brief periods, and peace of mind. With the Depositor Compensation Scheme now in place, the nominal safety of bank deposits has never been stronger. But safety of capital and growth of purchasing power are two different things, and confusing the two is one of the most costly long-term errors a saver can make.

For more on the risks of relying too heavily on term deposits, see our articles on seven risks of term deposits most savers overlook and when holding cash costs you money.

If you'd like to understand how your savings and investments are positioned relative to inflation, we'd welcome the opportunity to help. Get in touch with Become Wealth for an initial conversation.