Interest Deductibility and Bright-Line Rule Changes

Interest Deductibility Has Returned

Interest deductibility refers to a landlord’s ability to claim mortgage interest as a tax-deductible expense against rental income.

In recent years, the ability to claim interest deductions on residential investment properties was progressively restricted. This increased taxable rental income for many investors and reduced after-tax returns.

However, the Government has now reversed these rules.

From 1 April 2024 to 31 March 2025, investors were able to claim 80% of their mortgage interest costs as a deduction. From 1 April 2025 onwards, mortgage interest on residential investment properties became fully deductible again. This applies regardless of when the property was purchased or when the loan was taken out.

For many landlords, this means:

• Lower taxable rental income
• Reduced income tax obligations
• Improved property cash flow
• Greater certainty when assessing investment returns

However, mortgage interest is only one part of the rental property tax equation. Understanding which expenses can be claimed and how rental income is taxed remains essential. Our guide to tax on rental income in New Zealand explains the key rules landlords should be aware of.

Example of Interest Deductibility

Let’s say a rental property has a mortgage of $600,000 with annual interest costs of $36,000.

Under the current rules, the full $36,000 interest expense can generally be claimed as a deduction against rental income, reducing the investor’s taxable profit.

This can make a substantial difference to annual tax obligations, particularly for highly leveraged property investors.

While this can result in meaningful tax savings, landlords should also be actively monitoring their rental income, expenses and loan costs throughout the year.

Using a structured tracking system can make budgeting and tax planning much easier. Our free monthly cashflow spreadsheet for rental income is designed to help property investors keep track of rental property performance and identify potential issues before they become larger problems.

The Bright-Line Test Has Been Reduced

The bright-line test is designed to tax gains made from the sale of residential property within a specified ownership period.

For property sales entered into on or after 1 July 2024, the bright-line period has been reduced to two years. This replaces the previous five and ten-year bright-line periods that applied to many residential properties.

In practical terms, this means that if a residential investment property is owned for more than two years before being sold, any gain is generally not taxable under the bright-line rules.

However, this does not mean all property sales are automatically tax-free.

Other Property Tax Rules Still Apply

A common misconception is that once the bright-line period expires, any profit from selling a property is exempt from tax.

This is not necessarily the case.

Other tax provisions may still apply, including situations where:

• The property was purchased with the intention of resale
• Property dealing, development, subdivision or building activities are involved
• Associated person rules apply

The bright-line test is only one of several provisions Inland Revenue can use to assess whether a property sale should be taxed.

Rental Loss Ring-Fencing Remains

While full interest deductibility has returned, residential rental loss ring-fencing rules remain in place.

This means rental losses generally cannot be offset against salary, wages or other forms of income.

Instead, excess losses are carried forward and can usually be used against future rental profits or taxable gains from residential property.

For investors with multiple properties or significant interest costs, understanding how ring-fencing interacts with deductible expenses remains important.

What These Changes Mean for Investors

The return of full interest deductibility and the shorter bright-line period represent a more favourable environment for residential property investors than existed several years ago.

For many landlords, the changes improve cash flow, reduce annual tax costs and provide greater flexibility when considering future property transactions.

However, property tax rules remain complex. The interaction between interest deductions, ring-fencing, bright-line provisions, ownership structures and trust arrangements can have a significant impact on your overall tax position.