Debt-to-Income Ratio (DTI) in New Zealand: How It Works and How to Improve Yours

What Is a Debt-to-Income Ratio?

Since 1 July 2024, the Reserve Bank (RBNZ) has required banks to limit high-DTI lending. If your total debt exceeds six times your gross annual income, most banks cannot approve a standard owner-occupier mortgage unless they have remaining room under their regulatory quota. For investment property lending, the threshold is seven. These rules directly affect whether many New Zealand borrowers are approved or declined.

In plain terms, your debt-to-income ratio (DTI) is your total debt divided by your gross annual income, expressed as a multiple. A DTI of 5 means you owe five times your annual pre-tax earnings. A DTI of 6 means six times. Unlike the US system, which measures monthly debt payments as a percentage of monthly income, New Zealand's system measures total outstanding debt against annual income and expresses it as a simple ratio.

The biggest surprise for most borrowers is which debts count. Credit card limits, overdraft facilities, buy-now-pay-later (BNPL) accounts, and student loans all feed into the calculation, even when the balance is zero. A $15,000 credit card you keep for emergencies adds $15,000 to your total debt for DTI purposes. Marcus Mannering, Wealth and Lending Specialist at Become Wealth, sees this regularly:

"The borrowers who run into DTI issues are often surprised by what counts as debt. I regularly see people with two or three credit cards they barely use, each adding thousands to their total. Cancelling those cards a few weeks before applying is the simplest thing you can do to improve your position."

If you have searched this topic before, you may have found US content describing DTI as a percentage of monthly income. Applying a US benchmark of 36% or 43% to a New Zealand mortgage application will produce misleading conclusions. The two systems measure fundamentally different things.

How New Zealand's DTI Differs from the US System

The US system divides monthly debt payments by monthly gross income and expresses the result as a percentage. A borrower could have a low US-style DTI (small monthly payments relative to income) while still breaching the New Zealand threshold (high total debt relative to income), or the reverse. If you have seen a "good DTI" figure of 36% online, that number has no bearing on a New Zealand mortgage application.

New Zealand's DTI framework sits within the RBNZ's BS20A prudential standard, which governs how registered banks manage high-DTI residential lending. (BS20A is the regulatory document setting out the rules banks must follow; the RBNZ is currently developing a replacement Lending Standard under the Deposit Takers Act 2023, though BS20A remains the operative framework.) The DTI thresholds, along with LVR restrictions and each bank's own affordability test, collectively determine how much you can borrow.

How to Calculate Your DTI

DTI = Total debt ÷ Gross annual income

Base case: A couple with combined gross earnings of $150,000 per year is applying for a $750,000 mortgage. One partner has a $20,000 student loan and a $10,000 car loan. They hold one credit card with a $5,000 limit and a zero balance.

• Total debt: $750,000 + $20,000 + $10,000 + $5,000 = $785,000
• DTI: $785,000 ÷ $150,000 = 5.23

That sits below the owner-occupier threshold of 6.

Variation: Suppose the credit card had a $15,000 limit instead of $5,000, and the couple also held a $20,000 overdraft facility they never used. Total debt becomes $750,000 + $20,000 + $10,000 + $15,000 + $20,000 = $815,000, pushing DTI to 5.43.

After cancelling both: Closing the $15,000 card and the $20,000 overdraft before applying removes $35,000 from total debt, bringing it to $780,000 and DTI to 5.20. Revolving credit facility limits count as debt regardless of whether any money is owed on them.

What Counts as Debt

Banks include all of the following when calculating your DTI:

• The mortgage you are applying for
• Any existing mortgage debt
• Student loans
• Personal loans
• Car loans and hire purchase agreements
• Credit card limits (the full approved limit, even if the balance is zero)
• Overdraft facility limits (the facility size, not the drawn amount)
• BNPL commitments (most Tier-1 banks now include these under CCCFA interpretation, though the method of assessment differs between lenders; some count the outstanding balance while others factor in the total facility limit)
• Any guarantor obligations you carry for someone else's borrowing

The revolving credit point is where borrowers are caught off guard most often. It is common to see applicants carrying two or three cards they rarely use, each with a $5,000 to $15,000 limit, adding tens of thousands of dollars to assessable debt before they have spent a cent. Cancelling unused credit facilities before applying is typically the single highest-impact step a borrower can take. It is the first thing an experienced mortgage adviser will check.

What Counts as Income

Gross (pre-tax) income from the following sources is generally included:

• Wages and salary
• Self-employment income (banks typically discount this, often using an average of two or more years of financial statements and sometimes applying a further reduction; the size of the discount varies materially between lenders)
• Rental income (commonly assessed at 75% to 80% of gross rent, with the exact percentage set by each bank's own credit policy)
• Regular bonuses and overtime (usually averaged over one to two years rather than taken at face value)
• Government benefits, where they are ongoing
• Investment income

Two borrowers with identical headline incomes can produce meaningfully different DTI calculations depending on how much of their earnings come from variable sources and which bank they apply to. Self-employed borrowers and those with significant rental income tend to encounter the widest variation between lenders.

The RBNZ Thresholds and the Speed Limit

Under the RBNZ's DTI framework, registered banks must comply with two caps:

• Owner-occupiers: No more than 20% of new owner-occupier lending may have a DTI above 6
• Investors: No more than 20% of new investor lending may have a DTI above 7

The 20% figure is the "speed limit." A DTI above the threshold does not trigger an automatic decline. If your DTI is 6.5 as an owner-occupier, the bank can still approve the loan provided it has remaining capacity within its high-DTI quota. Banks manage these quotas actively, and availability shifts from month to month. A borrower declined at one bank in a tight quota period may find approval at another with more room, or at the same bank a few weeks later.

The RBNZ reviewed the DTI settings in October 2025 and decided to keep them unchanged, noting they remain calibrated to limit high-risk lending in housing upswings and periods of low interest rates. From 2026, the new Financial Policy Committee will review DTI and LVR settings at least annually, with the ability to adjust thresholds if risks become elevated.

A Good DTI Is Not the Same as the Maximum DTI

A DTI of 6 is the regulatory ceiling for standard lending, not a target. Borrowers with a DTI of 4 to 5 will generally find the mortgage more manageable over time, particularly if interest rates rise or household income drops temporarily. To make this concrete: on a $150,000 household income, a DTI of 5 means $750,000 of total debt and approximate monthly mortgage repayments of around $4,500 at a 6% interest rate over 30 years. A DTI of 6 means $900,000 of total debt, pushing monthly repayments to roughly $5,400. That $900 per month difference compounds during periods of higher rates or reduced income.

DTI Does Not Replace LVR

DTI restrictions sit alongside LVR restrictions (loan-to-value ratio, which governs your deposit requirement) and the bank's own serviceability or affordability test. All three operate simultaneously, and the tightest one determines how much you can borrow. DTI limits how much debt you can carry relative to your income. LVR limits how much you can borrow relative to the property's value. They serve different purposes and apply independently.

For most borrowers, especially those purchasing at lower price points, the serviceability test is the binding constraint. Banks apply a test interest rate well above the current market rate to check borrowers can still afford repayments if rates rise. DTI tends to become the limiting factor for higher-income households taking on large mortgages, or for investors with existing debt across multiple properties.

One important distinction: DTI restrictions apply only to registered banks regulated by the RBNZ. Non-bank lenders such as Resimac, Bluestone, and Liberty are not subject to these rules. For borrowers with a high DTI who can demonstrate serviceability, a non-bank mortgage may be a viable path, though typically at a higher interest rate.

How New Zealand Compares Internationally

New Zealand's 6× owner-occupier threshold is relatively generous by international standards, though direct comparisons require a caveat. Both the UK and Ireland use loan-to-income (LTI) ratios, which measure only the mortgage loan against income. New Zealand's DTI includes all debt in the numerator, so the numbers are not directly equivalent.

Under the Bank of England's LTI flow limit, UK lenders must keep high-LTI lending (at or above 4.5× income) to no more than 15% of new mortgage volume. Under the Central Bank of Ireland's mortgage measures, first-home buyers face a 4× LTI limit and subsequent buyers face 3.5×, with a 10% speed limit for above-threshold lending. Against those benchmarks, New Zealand's 6× threshold with a 20% speed limit gives borrowers considerably more room before hitting the regulatory ceiling.

That relative generosity reflects New Zealand's high house-price-to-income ratios. Auckland's median dwelling value has consistently sat at around seven to eight times the median household income in recent years. A tighter cap modelled on UK or Irish settings would have excluded a large share of the market from bank lending when the rules took effect. It also explains why advice and calculators from UK or Australian financial sites often feel conservative when applied to a New Zealand borrowing scenario.

When DTI Rules Do Not Apply

Several categories of lending sit outside the DTI restrictions entirely:

• New builds: Construction loans and purchases of newly built homes within 12 months of the code compliance certificate being issued are exempt. This makes new builds a particularly useful option for first-home buyers and other borrowers whose DTI would otherwise exceed the threshold.
• Kāinga Ora lending: Loans originated through Kāinga Ora programmes, including the First Home Loan, are not subject to DTI caps.
• Refinancing: Moving your existing mortgage to a new lender without increasing the loan amount is exempt.
• Portability: Transferring your loan to a different property without increasing the balance.
• Bridging finance: Short-term lending to bridge the gap between buying a new property and selling an existing one.
• Property remediation: Lending to repair defective buildings, such as weather-tightness issues.

The new-build exemption is worth highlighting. Buying off the plans or choosing a recently completed dwelling sidesteps the DTI restriction entirely, while also qualifying for LVR concessions on new builds. For borrowers weighing new builds against existing properties, the DTI exemption is a meaningful factor.

How to Improve Your DTI Before You Apply

Because DTI is a ratio, you can improve it by reducing debt, increasing income, or both. Most of the quick wins sit on the debt side.

Reduce Your Debt Exposure

• Cancel unused credit cards and overdraft facilities. Close them well before you apply, and allow a few weeks for the closure to be reflected in your credit file.
• Pay off or consolidate small debts. A $3,000 personal loan and a $2,000 BNPL balance may seem minor, but they add $5,000 to your numerator. Clear any active BNPL accounts and close them entirely; leaving the account open can still count against you with some lenders.
• Consider clearing your student loan if it is small and you are close to the threshold. A $10,000 student loan balance on a $150,000 income shifts your DTI by only 0.07. Minor in isolation, but if your DTI is 6.04 it could matter. Weigh this against the alternative: putting the same $10,000 toward a larger deposit reduces the mortgage you need and also lowers DTI. The right choice depends on which side of the threshold you are on and whether the deposit increase meaningfully changes your LVR position.
• Avoid new debt in the months before applying. A new car loan or hire purchase agreement taken on six months before your mortgage application directly increases your DTI.

Increase Your Assessable Income

• Apply jointly. Adding a partner or co-borrower's income to the application increases the denominator. A single earner on $100,000 seeking a $600,000 mortgage has a DTI of 6.0. Adding a partner earning $60,000 drops it to 3.75.
• Document all income sources. Boarder income, consistent overtime, or a side income can be included if you have records to substantiate it. Banks will want evidence over months or years, so start documenting early.
• Use a KiwiSaver Scheme first-home withdrawal to reduce the mortgage you need. Withdrawing from your KiwiSaver Scheme to increase your deposit means borrowing less, which directly lowers your DTI. In the base-case example above, a $30,000 KiwiSaver Scheme withdrawal would reduce the mortgage from $750,000 to $720,000, bringing total debt to $755,000 and DTI from 5.23 to 5.03.
• Time your application after a pay rise or promotion. If a salary increase is imminent, waiting a pay cycle or two may shift your DTI enough to matter.

Consider Structural Options

If reducing debt and increasing income still leave your DTI above the threshold, the exemptions listed earlier create genuine alternatives. Purchasing a new build removes the DTI constraint entirely. A non-bank lender can approve lending beyond the RBNZ caps, though at a higher cost. And the 20% speed limit means your bank may still have quota available for above-threshold borrowers with strong overall profiles.

Frequently Asked Questions

Can a mortgage adviser help me get approved above the DTI threshold?

An adviser cannot override the RBNZ rules, but they can identify which banks have remaining speed-limit quota, structure your application to minimise assessable debt, and recommend timing or lender selection that improves your chances. The variation in how different lenders treat BNPL, self-employment income, and rental income means an adviser with access to multiple banks can often find a path the borrower would miss on their own.

Do the DTI rules apply if I am topping up my existing mortgage?

Yes. A top-up increasing your loan balance is treated as new lending and is subject to DTI restrictions. Refixing or restructuring at the same balance is exempt, but adding to it is not.

Do non-bank lenders have to follow DTI rules?

No. The RBNZ's DTI restrictions apply only to registered banks. Non-bank lenders can approve lending at any DTI, provided their own credit criteria are met. The trade-off is usually a higher interest rate, and some non-bank lenders impose their own internal DTI limits even though they are not required to.

DTI Impact: Before You Apply

Add up every debt, including revolving credit limits, then divide by your gross household income. If you are above 6 as a prospective owner-occupier, the path forward usually starts with closing unused credit facilities and documenting every income source. If you are between 4 and 5, you have meaningful headroom.

If your DTI sits between 5.5 and 6.5, or you have non-standard income such as self-employment or rental earnings, or you are weighing a new build against an existing property, the interaction between DTI, LVR, and serviceability is worth modelling for your specific numbers. Small changes to debt or income can shift you from one side of the threshold to the other, and lender variance means the answer often differs depending on which bank you approach. You can run those scenarios with our lending team.