By Dave McCarry | 12 August 2026

Disclaimer: This article is for general information purposes only and does not constitute financial or tax advice. Every landlord's situation is different. Speak with a qualified accountant or tax adviser before making decisions based on this content.

Mortgage Interest Deductibility: What Wellington Landlords Can Claim in 2026

Most Wellington landlords know interest deductibility was removed. Fewer have actually sat down and worked out what the full restoration means for their tax return this year.

From 1 April 2025, you can claim 100% of the interest on your residential rental mortgage. Not 80%. Not 50%. All of it. The 2026 income year is the first complete year you've been able to do this since 2021. If you haven't reviewed what you're entitled to claim, this is the time to do it.

A Quick History of Where This Has Been

The previous Labour government restricted interest deductibility from October 2021, phasing it out progressively to 0% by April 2023 for most existing properties. National reversed course in stages: 80% deductibility from 1 April 2024, then full restoration to 100% from 1 April 2025. The restriction rules have now been fully repealed.

If you were confused by the changing percentages over the last few years, you're not alone. We hear this question constantly from landlords in Karori, Thorndon, and Te Aro who aren't sure what they could actually claim in any given year. The answer from April 2025 is simple: all of it.

What This Is Actually Worth for Your Wellington Property

Let's make this concrete. If you have a $600,000 mortgage at 6.5% interest, your annual interest cost is around $39,000. In the 2025 income year you could claim 80% of that ($31,200). From 1 April 2025 you can claim the full $39,000.

The difference: an extra $7,800 in allowable deductions. At a 33% marginal tax rate, that's roughly $2,574 back in your pocket compared with 2024. For landlords whose properties were subject to a complete interest denial under the previous rules, the difference is significantly larger. On that same $39,000 of interest, moving from 0% to 100% deductibility produces a tax saving of around $12,870 at 33%, or just over $15,210 at 39%.

For example, on an $800,000 rental mortgage at 6%, the annual interest is around $48,000. At a 33% marginal tax rate, that $48,000 deduction has a potential tax value of $15,840, although ring-fencing may defer when that benefit can be used. At 39%, the potential value is just under $18,720.

This is one of the most material changes to the financial position of Wellington landlords in the last decade. It's worth getting it right on your return.

What You Can and Cannot Claim

The interest component of your mortgage repayments is deductible. The principal component is not. These are two different things.

Interest is the cost of borrowing money. When you make a mortgage repayment, part of it reduces the loan balance (principal) and part of it covers the interest the bank charges for that month. Only the interest portion can be claimed as a rental expense. Your mortgage statement or annual bank interest certificate will show you exactly how much interest you paid across the year.

A few things to watch:

• Revolving credit and offset mortgages require care. If personal spending runs through the same revolving credit account as your rental mortgage, you can only claim interest on the rental property portion. If the account has been drawn on for personal purposes, you'll need to apportion carefully.
• Loan establishment, refinancing, and break fees can have different tax treatments depending on the circumstances. Check these with your accountant rather than assuming a particular approach.
• Mixed-use properties require apportionment. If you live in part of the property and rent out the rest, only the interest attributable to the rental portion can be deducted.
• Renting out part of your own home is treated differently. You may be able to claim a proportion of interest and other expenses relating to the income-producing portion, but you will need to apportion between private and rental use. This is not the same as the rules for standalone investment properties.

What Else Can You Claim Alongside Interest?

Many landlords who've been focused on the interest question overlook other deductible expenses they're not claiming. The full list for Wellington landlords includes:

• Council rates
• Landlord insurance
• Property management fees
• Repairs and maintenance (not capital improvements)
• Accounting and tax agent fees
• Body corporate levies relating to operating and maintenance costs (for apartment owners — levies used for capital improvements are generally not deductible)
• Advertising and letting fees
• Travel costs for rental property visits (in some circumstances)

Capital improvements are not deductible. If you replace a deck, reconfigure the layout, or add a room, those costs increase the property's value and are treated as capital expenditure rather than an expense. General maintenance and repairs sit on the deductible side; structural or improvement work generally does not. If you're unsure which side of that line your project falls on, an accountant who works with rental properties is the right call.

If you're also thinking about chattels depreciation, that's a separate and often overlooked tax saving on items like carpets, heat pumps, and appliances. We covered that in detail here.

A note on property management fees: if you use a manager, those fees are fully deductible as a rental expense. If you want to understand the full cost breakdown, this post has the detail.

Ring-Fencing: The Rule Landlords Often Forget

Even with full interest deductibility restored, there's a rule that affects negatively geared properties: ring-fencing.

Under New Zealand's ring-fencing rules, rental losses can only be offset against other rental income. They cannot reduce your employment income or other income sources. If your interest and other expenses push your rental position into a loss, that loss is carried forward and can be used against rental income in future years.

This matters for landlords whose Wellington properties are negatively geared, particularly where high mortgage balances exceed current rental yields. Ring-fencing means the tax benefit of the loss may be deferred rather than immediate. Your accountant can help you model this if it applies to your situation.

What Records IRD Expects You to Keep

IRD's IR264 Rental Income guide, updated in March 2026, is the most useful reference for what you need to retain. At minimum, hold onto:

• Annual mortgage interest certificates from your bank
• Mortgage statements showing the interest-versus-principal breakdown
• Any refinancing or loan restructure documentation
• Bank statements if you use a revolving credit or offset facility
• Records of when the loan was drawn down and for what purpose

Keep these records for seven years. That's IRD's standard retention requirement for tax records, and it's the practical window for any review or audit.

Filing Your 2026 IR3

The 2026 income year runs from 1 April 2025 to 31 March 2026. If you're filing without a tax agent, the deadline is 7 July 2026. If you're using a tax agent, they operate under an extended deadline (typically 31 March 2027) through IRD's tax agent extension scheme.

If you missed the July deadline as a self-filer, it's worth engaging a tax agent who works with rental property investors. They can often manage late filing, ensure you're claiming everything you're entitled to, and reduce the risk of errors that trigger IRD queries.

Frequently Asked Questions

Can I claim 100% of my mortgage interest on my Wellington rental property?

Yes. From 1 April 2025, the full restoration of interest deductibility allows Wellington landlords to claim 100% of interest paid on loans used for residential rental properties. This applies regardless of when the property was purchased or when the loan was originally drawn down.

What is the difference between claiming 80% and 100% interest deductibility?

On $39,000 of annual interest, moving from 80% (the 2025 income year rate) to 100% (from April 2025) means an extra $7,800 in deductible expenses. At a 33% marginal tax rate, that's roughly $2,574 more in your pocket annually. For landlords whose properties were subject to a complete interest denial under the previous rules, the cumulative difference is far more significant.

Does interest deductibility apply to new builds differently in 2026?

No. From 1 July 2024, new builds are treated the same as existing properties under both the bright-line test and interest deductibility rules. The separate new-build treatment that applied between 2021 and 2024 no longer exists.

Can I claim interest if my rental property is held in a trust or company?

Yes. The 100% interest deductibility applies to residential rental properties held through trusts, companies, and LookThrough Companies (LTCs), not just individual ownership. The standard apportionment and ring-fencing rules still apply in the same way they do for individual landlords.

What happens if my rental expenses exceed my rental income?

If your deductible expenses (including interest) exceed your rental income, you have a rental loss. Under New Zealand's ring-fencing rules, that loss can only be offset against other rental income, not against wages or other income. The loss carries forward and can be applied against rental income in future years.

The restoration of full interest deductibility is the most significant tax shift for Wellington landlords since 2021. For most property investors in suburbs like Kelburn, Karori, and Brooklyn, the savings are in the thousands of dollars per year. Making sure you're claiming everything you're entitled to, keeping the right records, and understanding ring-fencing is worth the time to get right.

If you'd rather hand the day-to-day management of your Wellington rental to someone who tracks the compliance calendar, handles tenant selection, and keeps your property financially optimised, we'd be glad to talk. Get in touch with Dave at Propertyscouts Capital City.

About Dave McCarry
Dave McCarry is the owner of Propertyscouts Capital City in Wellington and has worked in property, business, and customer service for many years. Since becoming a property investor in 2009, he has built a strong reputation for practical advice, strong tenant selection, and hands-on property management focused on protecting landlords' investments and maximising returns.