Most managed funds and KiwiSaver are PIEs. Tax is capped at your PIR — a maximum of 28%.
We tax your full return at your PIR, which is conservative: real PIE funds don’t tax NZ and Australian share capital gains, so your actual tax may be lower and your balance higher.
Projected balance after 20 years
$37,330
You put in
$25,000
Investment growth
$12,330
Tax & fees paid
$4,795
$4,795 tax · $0 fees
How your balance builds
Year-by-year breakdown
| Year | Contributed | Growth | Balance |
|---|---|---|---|
| 1 | $2,200 | $61 | $2,261 |
| 2 | $3,400 | $168 | $3,568 |
| 3 | $4,600 | $323 | $4,923 |
| 4 | $5,800 | $528 | $6,328 |
| 5 | $7,000 | $785 | $7,785 |
| 6 | $8,200 | $1,095 | $9,295 |
| 7 | $9,400 | $1,461 | $10,861 |
| 8 | $10,600 | $1,885 | $12,485 |
| 9 | $11,800 | $2,369 | $14,169 |
| 10 | $13,000 | $2,915 | $15,915 |
How this calculator works
- Returns compound monthly, and each contribution is invested at the start of the month so it earns from then on.
- The annual fund fee is deducted from your balance each month — over decades, fees make a real dent, which is why we let you include them.
- PIE funds and KiwiSaver: tax is squared up once a year at your PIR (capped at 28%), the way Inland Revenue collects it — so your money compounds untaxed through the year. We tax the full return, which is conservative, because real funds don’t tax NZ and Australian share capital gains.
- Savings and term deposits: RWT is taken off as the interest is paid, so we deduct it each month at your chosen rate (up to 39%).
- The return rate is fixed for the whole term. Real-world returns go up and down, and can be negative in any given year.
- Figures are in today’s dollars (no inflation adjustment) and don’t include KiwiSaver employer or government contributions. This is general information, not financial advice.
What is my RWT rate?
Resident withholding tax (RWT) is the tax your bank takes off the interest you earn — on savings accounts, term deposits and the like — before it reaches your account. You choose an RWT rate that matches your income tax rate, so you don’t get a surprise bill (or leave money sitting with Inland Revenue) at the end of the year.
Your rate is based on your total taxable income for the year:
| Your total taxable income | RWT rate |
|---|---|
| Up to $15,600 | 10.5% |
| $15,601 – $53,500 | 17.5% |
| $53,501 – $78,100 | 30% |
| $78,101 – $180,000 | 33% |
| $180,001 and over | 39% |
- If you haven’t given your bank your IRD number, they must deduct RWT at 45%.
- Given your IRD number but never picked a rate? The default is 33%.
- You can tell your bank your rate — and change it if your income changes — at any time.
- Investing through a managed fund or KiwiSaver instead? Those are PIEs, so you use a prescribed investor rate (PIR), which is capped at 28% — not an RWT rate.
Rates are for the 2025/26 tax year. Confirm your rate with Inland Revenue.
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