Deducting costs from rental income
Question from Ryan updated on 22nd August 2018:
My partner and I have just bought our first four bedroom home and are looking to rent out the other rooms to flatmates to help pay the mortgage. We understand that we have to declare this as income, however I was just wondering if we can deduct the mortgage interest costs from this income?
Our mortgage is $600,000 and our interest is going to be approximately $26,700 this year. We are renting out three bedrooms in Auckland for a total of $620 a week or $32,240. Can we deduct the $26,700 of interest off the $32,240 of income that we will receive?
Our expert Matthew Gilligan responded:

You are right that you need to declare the income from the flatmates as taxable income. While there is an exemption for providing boarding services, if you have flatmates that are paying rent and effectively acting as tenants, then it is taxable income.
You are permitted a deduction for expenditure that is incurred in relation to deriving this income. This means you will be permitted a deduction for interest, but it will not be the total interest paid.
You need to apportion the property between private and rental use and claim the relevant proportion of the interest against the rental income. As a starting point, if three of four bedrooms are rented you may be looking at claiming 3/4 of the interest and other property holding expenses as deductible, although this will depend on the facts.
Matthew heads GRA's specialist property and asset planning division. He helps clients create optimal tax structures and build wealth through property. He has an extensive buy-to-hold property portfolio, is currently involved in over a dozen developments, and is author of two books - Property 101 and Tax Structures 101.Search the Ask an Expert archive
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