A joint mortgage is a home loan where two or more people are co-borrowers, sharing responsibility for the debt. In New Zealand, most couples buy together — but joint mortgages between friends, siblings, and other combinations are also possible. Understanding how income is assessed, how ownership is structured, and what happens if the arrangement changes is essential before you sign.
A NZ joint mortgage combines both borrowers' incomes for the DTI 6× borrowing cap, but makes all borrowers jointly and severally liable for 100% of the debt. The property ownership structure — joint tenancy or tenants in common — is a separate legal decision with major consequences if the relationship ends or one party wants to exit.
Who Can Apply for a Joint Mortgage in NZ?
NZ banks don’t restrict joint mortgages to couples or family members. You can apply jointly with:
- A partner or spouse (married, civil union, or de facto)
- A sibling or other family member
- A friend or colleague
- A parent (as a co-borrower, separate from a guarantor arrangement)
Up to four borrowers can typically be on a mortgage, though most banks prefer two. Adding more borrowers adds legal and administrative complexity.
How Income Is Assessed in a Joint Application
The primary benefit of a joint application is combined income, which increases your borrowing capacity under DTI rules.
Example:
- Borrower 1 salary: $75,000 → solo DTI 6× cap = $450,000
- Borrower 2 salary: $65,000 → solo DTI 6× cap = $390,000
- Combined income: $140,000 → joint DTI 6× cap = $840,000
Both borrowers’ incomes are combined — but so are their expenses and debts. Both borrowers’ student loans, personal loans, credit card limits, and living costs are assessed together.
All borrowers are equally responsible for 100% of the debt. This is not “each person owes their half” — if one borrower can’t pay, the other is fully liable for the entire mortgage. Banks treat it as joint and several liability.
Ownership Structures: Joint Tenants vs Tenants in Common
The mortgage and the property ownership are separate legal matters. When two people buy together, they need to choose an ownership structure for the title:
Joint tenancy
- Both owners hold an equal, undivided share
- Right of survivorship: if one owner dies, their share automatically passes to the surviving owner (overrides any will)
- Cannot leave your share to someone else in your will
- Common for married or long-term couples
Tenants in common
- Each owner holds a specified share (50/50, 60/40, 70/30 — any split is possible)
- Each owner’s share can be left to anyone in their will
- Better for unequal contributions (one person contributes more deposit), non-couples, or investors
- Common for friends, siblings, investment arrangements
Example of tenants in common split:
- Person A contributes $100,000 deposit
- Person B contributes $50,000 deposit
- Total deposit: $150,000 on a $750,000 property
- Agreed split: 60% (A) / 40% (B) on the title
Your lawyer will register the ownership structure on the title at settlement. Discuss this carefully with a lawyer before committing — changing it later is possible but involves legal cost.
See Joint Tenants vs Tenants in Common NZ for more detail.
Relationship Property Law and Joint Mortgages
For couples in a qualifying relationship (married, civil union, or de facto for 3+ years), the Property (Relationships) Act 1976 applies. This law means:
- Relationship property (typically the family home) is split 50/50 regardless of who contributed more to the deposit or mortgage
- The contribution of one partner’s KiwiSaver or inheritance to the deposit may still be treated as relationship property in many situations
- Separation triggers a legal process to divide the property
This is why separate property agreements (contracting out agreements) are sometimes used by couples who want to protect pre-relationship assets. These must be negotiated and signed before or early in the relationship, with each party getting independent legal advice.
Property Sharing Agreements for Non-Couples
If you’re buying with a friend, sibling, or business partner, a property sharing agreement is essential. This is a private legal document that covers:
- Each person’s ownership share and initial contribution
- How mortgage payments and ongoing costs are split
- What happens if one person wants to sell and the other doesn’t
- How the property is valued and priced if one person buys the other out
- What happens if one person stops making payments, loses their job, or dies
- How disputes are resolved
Without a property sharing agreement, you’re relying on general property law — which may not reflect your intentions. This agreement is separate from the mortgage and the title; it’s a contract between co-owners.
Cost of a property sharing agreement: approximately $500–$2,000 depending on complexity.
What Happens If One Person Wants to Sell?
For joint tenants: either party can technically force a sale (partition action) — but this is legally complex and uncommon.
For tenants in common: each owner’s share is separate. If one owner wants out, options include:
- The other owner buys out their share (refinancing to remove one borrower)
- Both agree to sell the property
Buying out a co-owner: requires the remaining owner to qualify for the full mortgage on their own income (subject to current DTI and LVR rules). If the remaining owner can’t qualify alone, the property typically must be sold.
Removing a borrower from a joint mortgage requires bank approval and refinancing — it’s not as simple as just agreeing between yourselves.
Joint Mortgages and First Home Buyer Entitlements
If any co-borrower has previously owned residential property, they may not qualify for first home buyer assistance:
- First Home Loan: all borrowers must be first home buyers
- KiwiSaver first home withdrawal: each co-borrower applies for their own withdrawal individually — one borrower’s previous ownership doesn’t prevent the other from withdrawing
- First Home Grant (Kāinga Ora): each applicant must qualify individually
Frequently Asked Questions
Can friends or siblings get a joint mortgage in NZ?
Yes. NZ banks don’t restrict joint mortgages to couples or family — you can apply jointly with a friend, sibling, parent, or anyone else. However, the absence of relationship property law protections for non-couples makes a formal property sharing agreement with an independent lawyer essential.
What does joint and several liability mean for a NZ mortgage?
Joint and several liability means every borrower is fully responsible for the entire debt, not just their share. If one co-borrower stops paying, the bank can pursue the others for the full outstanding balance. This applies regardless of any private agreement between co-owners about how costs are split.
What is the difference between joint tenants and tenants in common in NZ?
Joint tenancy means equal, undivided ownership with right of survivorship — if one owner dies, their share automatically passes to the survivor, overriding any will. Tenants in common means each owner holds a specified share (e.g., 60/40) that can be left to anyone in a will. Tenants in common is generally better for unequal contributions or non-couples.
Do both incomes count when applying for a joint mortgage in NZ?
Yes — combined gross income is used to calculate the DTI 6× cap. Two borrowers earning $70,000 and $65,000 have a combined DTI cap of $810,000, versus $420,000 and $390,000 individually. Both borrowers’ debts, credit card limits, and living expenses are also assessed together.
What happens to a joint mortgage if a couple separates in NZ?
Separation typically results in one partner buying out the other (requiring refinancing to remove one borrower and qualify solo under current DTI and LVR rules) or both agreeing to sell. The bank must approve any removal of a borrower — the remaining co-borrower must demonstrate solo serviceability, which can be difficult at current lending standards.