10 Common IR3 Mistakes NZ Kiwis Make 2025-26 & 2026-27 — Avoid IRD Penalties (myIR)

Filing an IR3 looks straightforward in myIR — until a small error triggers a review, a shortfall assessment, or a use-of-money interest charge. These are the 10 mistakes we see most often, each with a specific IRD fix.

Before you file, run our IR3 filing checker and work through the pre-filing checklist — most mistakes get caught in the preparation phase.

1. Wrong Prescribed Investor Rate (PIR) on PIE income

The single most common error. If your PIR was too low (e.g. you stayed on 10.5% after a promotion), IRD reopens the PIE income at your marginal rate and charges tax on the difference.

Check your PIR: If your taxable income was $14k or less in either of the last two years, 10.5% is right. $14k–$48k → 17.5%. $48k+ → 28%. See our PIR calculator.

Fix: If you were on the wrong PIR, IRD adjusts automatically in your end-of-year assessment. For the next year, update your PIR with your fund provider now.

2. Missing overseas income

CRS data exchange means IRD sees most foreign bank accounts, brokerage accounts (FIF), and foreign employment. Common misses:

• Bank interest under $1,000 — tiny amounts still count; you’ll trip the $50k FIF de minimis threshold one year sooner than expected
• Foreign dividends — fully taxable in NZ even if foreign tax was withheld (claim a foreign tax credit)
• Foreign pensions — a lump sum withdrawal from a UK/Australian super may be fully taxable if no FIF applied during accumulation
• Working-holiday income earned before becoming resident — still part-year taxable

Fix: Declare the income. If foreign tax was paid, claim a foreign tax credit up to the NZ tax on the same income. See our FIF calculator for overseas share holdings.

3. Forgetting a bright-line property sale

The bright-line test catches property sold within 2 years (for sales on or after 1 July 2024) or 5/10 years (for earlier purchases). Even if the property was your home for most of the ownership period, partial-use or investment-use periods can create a taxable portion.

Signs you need to check bright-line:

• Bought and sold within 2 years
• Rented it out at any point
• Subdivided and sold a lot
• Inherited a property and sold shortly after

Fix: Use our bright-line test calculator before filing. Bright-line gains are fully taxable as ordinary income.

4. Claiming non-deductible expenses

Non-deductible costs consistently appear on self-employment returns and get reversed:

Claimed	Why it fails
Home mortgage principal	Capital, not an expense
Commuting costs	IRD treats home-to-work travel as private
Ordinary clothing	Only protective or uniform clothing is deductible
Business meals for sole proprietor	Only if entertaining clients in specific cases
Gym memberships, personal phone	Personal benefit
Pre-business-start costs	Generally only from the date you commenced business

Fix: Only claim the business proportion of dual-purpose costs (phone, internet, vehicle), and keep logbooks where required. See our home office guide.

5. Mixing up gross and net rental income

Landlords who report gross rent without deductions overpay; those who net-off non-deductible costs create audit flags.

Include as deductions:

• Rates, insurance on the building
• Mortgage interest (fully deductible from 1 April 2025 onwards; phase-out rules applied in prior years)
• Property management fees, repairs, depreciation on chattels

Don’t deduct:

• Mortgage principal
• Improvements (capital — add to cost base)
• Personal use period costs

Fix: Use our rental income tax calculator to net off deductions correctly, and respect the residential rental ring-fencing rules on losses.

6. Claiming the IETC when ineligible

The Independent Earner Tax Credit (IETC) gives up to $520/year to earners $24k–$48k — but only if you did not receive any of these for any part of the tax year:

• Main benefit (Jobseeker, Sole Parent, Supported Living, etc.)
• NZ Super
• Veteran’s Pension
• Working for Families Tax Credits

Even one week on a benefit invalidates the full-year IETC claim.

Fix: Use our IETC calculator which checks exclusions automatically. If you wrongly claimed, IRD will reverse it and charge use-of-money interest.

7. Late filing without a tax agent

The standard IR3 deadline is 7 July. Miss it without being on a registered tax agent’s client list before 31 March, and you get:

• $50 late-filing penalty (or $250 for companies/trusts), doubling at 30+ days
• Use-of-money interest on unpaid terminal tax from 7 February (nearly 11% p.a. as of 2026)
• Higher audit risk in subsequent years
• No 31 March 2027 extension for the current year (signing up with an agent after 31 March doesn’t roll back)

Fix: File on time or sign up with a registered tax agent before 31 March of the year after the tax year ends.

8. Wrong terminal tax date (or missing it)

Terminal tax is due 7 February after the tax year ends (e.g. 7 Feb 2027 for 2025-26) if you’re not on an agent’s list, or 7 April if you are.

If you owe terminal tax over $5,000, you’re automatically a provisional taxpayer next year — meaning you pay three instalments on 28 August, 15 January, and 7 May during the year.

Common errors:

• Paying terminal tax on 7 April without being on an agent’s list (penalty applies)
• Missing the first provisional instalment the following August
• Using the wrong payment reference code (causes payment mis-allocation)

Fix: Diarise both dates when you submit. Use our terminal tax calculator and provisional tax calculator.

9. Separate IR526 for donations

Donation tax credits (33.33% back on donations over $5 to approved donees) are not claimed on the IR3. They go on a separate IR526 form, which you can file anytime within four years.

Filing the IR526 with your IR3 is fine, but forgetting it altogether means losing the credit. Missing an IR526 is one of the most common unclaimed refund triggers.

Fix: File IR526 in myIR under “Donation tax credit”. Keep receipts for 7 years — IRD may request a sample.

10. Forgetting provisional tax already paid

If you paid provisional tax during the year, myIR usually pre-fills it — but if you paid into the wrong period, used the wrong reference, or paid across two IRD numbers (sole-trader + company), the payment can go missing from your IR3 reconciliation.

Fix: Before submitting, check the “Payments made” section matches your bank records. If a payment is missing, raise a myIR secure message before filing rather than after.

If You’ve Already Made a Mistake

Voluntary disclosure before IRD contacts you typically removes shortfall penalties. Disclose via myIR:

1. Amend the original return if within 4 years
2. Add a secure message explaining what changed and why
3. Pay any extra tax immediately — use-of-money interest still applies but penalties are waived

Leaving it until IRD asks questions usually triggers a 20% (unacceptable tax position) or 40% (gross carelessness) shortfall penalty on top of the missing tax.

Useful Guides and Calculators

• IR3 filing checker — do you actually need to file?
• IR3 pre-filing checklist — gather everything before logging in
• How to file an IR3 — step-by-step guide
• NZ tax refund timing 2025-26 — when to expect payment
• PIR calculator — right PIR for PIE income
• Bright-line test calculator — if you sold property
• Terminal tax calculator — confirm your terminal tax

Sources

• Filing your IR3 — IRD
• Shortfall penalties — IRD
• Voluntary disclosure — IRD
• PIE income and PIRs — IRD