Borrowing Capacity Guide - NZ Mortgage Calculator
💰 Borrowing Capacity Guide - New Zealand
Understanding borrowing capacity is crucial before house hunting. Banks assess your income, expenses, existing debts, and stress-test your ability to service a loan at higher interest rates. This guide explains exactly how banks calculate what you can borrow, what factors matter most, and strategies to maximise your borrowing power while staying financially secure.
How Banks Calculate Borrowing Capacity
Banks use sophisticated servicing calculators that consider multiple factors:
1. Income Assessment:
| Income Type | How Assessed | Notes |
|---|---|---|
| PAYE salary | 100% of gross income | Most reliable, fully counted |
| Bonuses/commissions | 50-100% average over 2 years | Must be consistent |
| Self-employed | Average net profit last 2 years | Requires tax returns |
| Rental income | 70-80% of gross rent | Accounts for vacancies/costs |
| Overtime | 50-80% if regular | Must prove consistent |
| Benefits (DPB/etc) | Varies by bank | Some banks don't count |
2. Expense Assessment:
Banks use the higher of:
| Household Size | Monthly Benchmark | Annual |
|---|---|---|
| 1 adult | $1,800-$2,200 | $21,600-$26,400 |
| 2 adults | $2,800-$3,500 | $33,600-$42,000 |
| 2 adults + 1 child | $3,500-$4,200 | $42,000-$50,400 |
| 2 adults + 2 children | $4,200-$5,000 | $50,400-$60,000 |
| 2 adults + 3+ children | $5,000-$6,000 | $60,000-$72,000 |
3. Existing Debts:
Banks deduct all debt obligations:
- Car loans: Full monthly repayment deducted
- Personal loans: Full monthly repayment deducted
- Student loans: 12% of gross income deducted (NZ repayment rate)
- Credit cards: 3-5% of limit deducted monthly (even if $0 balance)
- Afterpay/ZIP: Counted as available credit, reduces capacity
- BNPL services: Increasingly scrutinized by banks
$20,000 credit card limit reduces borrowing by $60,000-$100,000 even with $0 balance! Banks assume you could max it out anytime. Cancel unused cards before applying.
4. Stress Testing:
Banks test affordability at higher interest rates:
Debt-to-Income (DTI) Ratio
Reserve Bank guidance limits total lending:
DTI Examples:
| Annual Income | Max Debt (6x) | Max Debt (5x) |
|---|---|---|
| $60,000 | $360,000 | $300,000 |
| $80,000 | $480,000 | $400,000 |
| $100,000 | $600,000 | $500,000 |
| $120,000 | $720,000 | $600,000 |
| $150,000 | $900,000 | $750,000 |
The Servicing Calculation
Banks calculate maximum borrowing using this approach:
Factors That Reduce Borrowing Capacity
| Factor | Impact | Example |
|---|---|---|
| Credit cards | Huge reduction | $10K limit = -$30K-$50K borrowing |
| Car loan | $5 less borrowing per $1 repayment | $500/month = -$150K borrowing |
| Student loan | 12% of income unavailable | $80K income = -$9,600/year |
| Dependents | Higher expense benchmarks | Each child = -$700/month expenses |
| Self-employed | Lower income recognition | Must prove 2-year average |
| Probation period | May need to wait | Some banks want 3-6 months passed |
Strategies to Maximise Borrowing Capacity
Before Applying:
- Cancel unused credit cards: Each $10K limit reduces borrowing $30-50K
- Pay off small debts: Clear car loans, personal loans if possible
- Reduce credit limits: Lower limits on cards you keep
- Make voluntary student loan payments: Lower balance = lower ongoing deduction
- Build savings buffer: Shows financial discipline
- Tidy credit history: No missed payments 6 months before applying
- Avoid job changes: 3+ months in role preferred, 6+ better
Income Optimisation:
- Include all income sources: Bonuses, overtime, rental, dividends
- Self-employed: Ensure last 2 tax returns show strong profit
- Add partner income: Joint application increases capacity
- Prove consistency: Provide payslips showing regular income
Expense Management:
- Review actual spending: Reduce discretionary expenses 3 months before applying
- Bank statements matter: Banks review last 3-6 months
- Avoid gambling: Red flag for banks
- Minimise Uber Eats/takeaways: Shows poor money management
- No overdrafts: Sign of financial stress
Just because you CAN borrow an amount doesn't mean you SHOULD.
Leave 15-20% buffer below maximum borrowing for:
• Interest rate increases
• Unexpected expenses
• Job changes or income drops
• Life changes (kids, health)
Better to buy below budget than max out and face financial stress.
Bank Comparison
Different banks have different appetites:
| Factor | Conservative Banks | Moderate Banks | Aggressive Banks |
|---|---|---|---|
| DTI limit | 5x income | 6x income | Up to 7x in rare cases |
| Stress test rate | 9.0% | 8.5-8.75% | 8.5% |
| Self-employed | Strict, 2-year proof | 1-2 years | May accept 1 year |
| Rental income | 70% counted | 75% counted | 80% counted |
Tip: Use a mortgage broker to find which bank will lend you most. Don't just apply to your current bank.
🔢 Borrowing Capacity Calculations
Example 1: Single Person - Standard Employment
Profile: Sarah, 28, Auckland
- Gross income: $85,000/year ($7,083/month)
- After-tax income: $63,400/year ($5,283/month)
- Living expenses: $2,200/month (bank benchmark single person)
- Student loan: Yes (12% repayment = $10,200/year = $850/month)
- Credit card: $8,000 limit (unused)
- No other debts
Servicing Calculation:
Borrowing at Stress Test Rate (8.5%):
DTI Check:
Improvements:
Example 2: Couple - One Income, Debts
Profile: Mike & Emma, 32 & 30, Wellington
- Mike income: $95,000/year
- Emma income: $0 (stay-at-home parent)
- Combined after-tax: $70,300/year ($5,858/month)
- Living expenses: $3,800/month (couple + 1 child benchmark)
- Car loan: $450/month ($18,000 remaining)
- Credit cards: Mike $12,000 limit, Emma $5,000 limit
- No student loans
Servicing Calculation:
Borrowing at 8.5%:
After Improvements:
Example 3: Dual Income Couple - No Debts
Profile: James & Lisa, 35 & 33, Christchurch
- James: $78,000/year
- Lisa: $72,000/year
- Combined: $150,000/year
- After-tax: $111,000/year ($9,250/month)
- Living expenses: $4,500/month (2 adults, 2 children)
- No debts, no credit cards, no student loans
Servicing Calculation:
Borrowing at 8.5%:
DTI Check:
Result: Clean financial position = strong borrowing capacity. With $120K deposit, can purchase $738K property.
Example 4: Self-Employed Impact
Profile: David, 40, Auckland
- Business gross revenue: $180,000/year
- Net profit (last 2 years average): $85,000/year
- Banks assess on net profit, not revenue
Income Assessment:
Compared to PAYE:
| Scenario | Assessed Income | Max Borrowing |
|---|---|---|
| Self-employed | $85,000 | ~$425,000 |
| If PAYE employee | $180,000 | ~$900,000 |
Impact: Self-employed status reduces borrowing by 50%+ even with same revenue!
Example 5: Credit Card Impact Analysis
Testing credit card limit impact:
| Credit Card Limit | Monthly Buffer (3%) | Borrowing Reduction |
|---|---|---|
| $5,000 | $150 | -$46,000 |
| $10,000 | $300 | -$92,000 |
| $15,000 | $450 | -$138,000 |
| $20,000 | $600 | -$184,000 |
| $30,000 | $900 | -$276,000 |
Calculation basis: At 8.5% over 30 years, each $100/month repayment capacity = ~$30,667 borrowing.
3 cards with $10K limits each = -$276K borrowing power! Cancel unused cards immediately before applying for mortgage.
🌍 Real-World Borrowing Capacity Stories
Rachel, 29, teacher in Auckland, $72K income
First Application:
The Problem:
- Credit card 1: $12,000 limit (balance $800)
- Credit card 2: $8,000 limit (balance $0)
- Credit card 3: $15,000 limit (rewards card, unused)
- Total limits: $35,000
- Bank deducted $1,050/month (3% of limits)
The Fix:
Result:
- Reapplied 3 months later
- Approved for $438,000
- Increase of $158,000!
- Successfully purchased $530K apartment
Lesson: Unused credit cards are silent borrowing killers.
Tom & Sarah, combined $130K income, wanted $600K loan
Their Situation:
- Car loan: $650/month ($32,000 remaining, 4 years left)
- Bank approved: $415,000
- $185,000 short of goal!
The Math:
Their Decision:
- Used $32K from savings to pay off car loan
- Reduced house deposit from $150K to $118K
- Reapplied immediately
- Approved for $618,000
- Purchased $736K home (vs $533K before)
Analysis:
Spent $32K to unlock $203K more borrowing. Even with lower deposit (16% vs 20%), better outcome than keeping car loan.
Jason, 38, tradesman contractor
His Income:
The Problem:
- Had been claiming maximum business expenses
- Minimised tax (smart for tax, bad for borrowing)
- Bank only saw $71K income, not $165K revenue
- Approved for $380,000
- Needed $550,000
Strategic Fix (for next year):
- Reduced aggressive expense claims
- Paid more tax but showed higher profit
- Year 3: Net profit $95,000
- New 2-year average: $84,500
- Reapplied, approved for $520,000
Lesson: Self-employed need to balance tax minimisation vs borrowing power. Plan 2 years ahead.
Mark & Jenny, both 34, combined $145K income
6 Months Before Applying:
- Cancelled 4 unused credit cards ($43K limits)
- Paid off Mark's $16K car loan
- Made $8K voluntary student loan payment (Jenny)
- Reduced spending, built 3-month emergency fund
- Mark's employer confirmed in writing (off probation)
Application Time:
Results:
- Applied to 3 banks via mortgage broker
- Bank A offered: $710,000 (conservative)
- Bank B offered: $785,000 (moderate)
- Bank C offered: $820,000 (aggressive)
- Chose Bank B ($785K) as comfortable middle ground
- Purchased $850K home with $65K deposit (down payment assistance)
Lesson: Preparation matters. 6 months of financial discipline unlocked $200K+ extra borrowing.
🎯 Test Your Knowledge
Quiz on Borrowing Capacity in NZ
Frequently Asked Questions
How much can I borrow for a mortgage in New Zealand?
It depends on your income, regular expenses, existing debts and the lender tests, including a stress test of repayments at a higher rate. Banks check whether repayments fit comfortably within your income after living costs.
What is a debt-to-income (DTI) ratio?
It is your total borrowing as a multiple of your gross income. The Reserve Bank applies DTI limits that cap how much most owner-occupiers and investors can borrow relative to income.
Does a bigger deposit increase how much I can borrow?
A larger deposit lowers your loan-to-value ratio, widening your lender options and removing a low-equity premium, but your borrowing is still capped by what you can afford to repay.
What do banks include when assessing affordability?
Your income, regular expenses, other debts, and the stress-tested repayment on the new loan. Reducing debts and expenses before you apply can lift your borrowing power.
Situations like yours. The 4 situations worked through above sit alongside 40 more about buying a first home, each with the sums shown.