RBNZ Debt-to-Income Limits in NZ: What First-Home Buyers Need to Know
How the Reserve Bank DTI rules cap what you can borrow — and why your mortgage ceiling might be 6× gross income before the bank even looks at your spending.
When people talk about “how much the bank will lend me,” they usually picture income minus expenses. In New Zealand, there is often a hard ceiling before that conversation even starts: the Reserve Bank’s debt-to-income (DTI) framework. If you hit the cap, you cannot borrow more — even if your day-to-day budget looks fine.
Owner-occupiers: the 6× rule of thumb
For most owner-occupier buyers, total debt (including the new mortgage you are applying for) is assessed against a multiple of gross household income. Think of it as: “All-in debt cannot exceed roughly six years of gross income.” (Investor rules differ — see our glossary entry on DTI for the distinction.)
Example: combined gross income of $160,000 → a DTI-driven ceiling in the ballpark of $960,000 of total debt. Existing car loans, personal loans, and credit card limits (not just balances) can all eat into that headroom.
Why DTI bites before “serviceability”
Serviceability asks whether you can afford repayments at the bank’s stress-test rate. DTI asks a separate question: whether your total debt is allowed at all relative to income. High earners with modest expenses sometimes discover that DTI binds first — the opposite of what they expected.
What counts as “debt” for DTI
- Mortgage you are applying for (and existing property debt)
- Personal loans, car finance, buy-now-pay-later where treated as debt
- Student loans (treated per lender policy)
- Credit cards — often assessed on limit, not just balance
That last point surprises people who “pay the card off every month.” For DTI and serviceability, the limit can still matter. Our guide on credit cards and BNPL walks through the mechanics.
How this connects to first-home buyers
If you are stretching toward a higher price bracket, DTI is the silent veto. Pair it with LVR (deposit %) and stress-test serviceability, and you get three separate gates — whichever is tightest wins.
See your own DTI position
MortgageReady models NZ income tax, ACC, KiwiSaver, and common deductions, then applies DTI alongside stress-tested borrowing scenarios so you can see which limit is binding. Browse the Mortgage Glossary for plain-language definitions of DTI, borrowing power, and surplus income.
When you are ready to speak to a broker or bank, export a free summary PDF from your dashboard — it is designed to support that first meeting.