NZ Rental Property Cash Flow Calculator
This calculator projects the full after-tax cash flow of a New Zealand rental property, reflecting the 100% mortgage interest deductibility restored from 1 April 2025 and the ring-fencing rules that still apply to rental losses. You enter your weekly rent and vacancy rate, your loan balance, interest rate and remaining term, plus the property value for yield. You then add annual operating costs: council rates, insurance, property management fees, repairs and maintenance, accounting fees, and chattels depreciation, before selecting your marginal tax rate. Results appear across three tables: effective rental income and taxable income or loss once interest, opex and depreciation are deducted; tax payable, or, if you make a loss, confirmation it is ring-fenced and carried forward rather than offsetting your salary; and the actual cash flow, showing the principal and interest split, operating costs, tax paid, and net annual and weekly cash flow, alongside gross and net rental yield. A results banner flags whether you are running positive or topping up from other income, common in the early years of NZ property ownership. Tax profit and cash flow differ, since principal is not deductible and depreciation is not a real cash cost, so treat every figure as an indicative estimate, as actual results depend on interest rates, vacancy, maintenance and future tax law changes.
Rental income
Mortgage
Annual operating expenses
Your tax situation
Tax vs cash flow - two different pictures
A common confusion: tax profit is NOT the same as cash flow. Mortgage interest is a deductible expense, but principal repayments are not. Conversely, depreciation is a deductible expense but no actual cash changes hands. This calculator shows both views side by side.
Ring-fencing rules (Income Tax Act 2007 s EL 1-20)
Even with 100% interest deductibility restored, rental losses are ring-fenced. This means:
- You CAN'T use rental losses to reduce tax on your salary or wages.
- Losses carry forward to offset future rental income or bright-line gain on sale.
- You choose either portfolio ring-fencing (losses pooled across all your rentals) or property-by-property ring-fencing. The choice is locked in after your first year.
- Ring-fencing doesn't apply to most companies whose core business isn't residential property.
Operating expenses checklist
Deductible: council rates, insurance (building + landlord), property management fees, advertising for tenants, repairs and maintenance (not improvements), accountant fees, legal fees for leases, travel to inspect property, utilities you pay, chattels depreciation, body corporate fees for investment properties.
NOT deductible: principal repayments on mortgage, capital improvements (extensions, new deck - add to cost base), purchase-related legal fees (cost base), private use portion, your own labour on maintenance.
Sources
- IRD - Renting out residential property
- IRD - Residential property interest limitation rules
- IR264 Rental income guide (March 2026)
Cash flow projections are indicative only. Actual results depend on interest rate changes, vacancy, maintenance surprises, and tax law. Most investors find year 1-5 cash flow is negative even at healthy yields - the rationale is typically long-term capital growth, not current cash return.