Co-borrower or guarantor: who owes what

Three arrangements Australians routinely confuse

A co-borrower is a party to the loan contract. They owe the debt, appear on the loan in their own name, and the loan appears on their credit file. A guarantor is not a party to the loan and owes nothing while it performs; they sign a separate guarantee, usually supported by a mortgage over their own property, and become exposed only if the guarantee is called. A person on the title who is not on the loan is a third arrangement again, and lenders rarely permit it because it leaves them with a mortgagor who is not a debtor.

These are not variations on a theme. They differ in who is liable, in what appears on whose credit file, in what happens on separation or death, and in whose property can be sold. Getting the wrong one because it was the easiest to arrange at application is a problem that surfaces years later, usually at the worst moment.

Ownership share and liability are also separate questions. Holding 20 per cent of the title does not make you liable for 20 per cent of the loan, and paying 80 per cent of the repayments does not give you 80 per cent of the property. Whatever the two of you agreed verbally, the loan contract and the title determine the legal position.

Joint and several liability, in plain terms

Joint borrowers are each liable for the entire debt, not a share of it. If two people borrow $800,000 and one stops paying, moves overseas, or becomes bankrupt, the lender can pursue the other for the whole $800,000 and is under no obligation to chase the first one first or to split the claim. There is no such thing as being responsible for half a mortgage.

The same logic applies to arrears. Missed repayments are reported against both credit files regardless of whose bank account the direct debit failed from, and a default on a joint loan sits on the file of a borrower who paid their half diligently for five years. This is the single most common unpleasant surprise in a joint loan that goes wrong.

It also constrains future borrowing. Most lenders assess the full joint loan against each borrower when either of them applies for something new, so a co-borrower on a $800,000 loan is treated as carrying $800,000 of debt even if the other party services all of it. Some lenders will apportion the liability where there is documented evidence the other borrower makes the repayments and can afford them, but the policy varies and the generous treatment is the exception. Going onto a family member’s loan to help them qualify can quietly close down your own borrowing for years.

What a limited guarantee limits

The common family structure is a limited guarantee: the guarantor’s liability is capped at a stated dollar amount and secured by a mortgage over a specific property, usually sized to bring the overall security position to the point where lenders mortgage insurance is not required. Take a $700,000 purchase where the buyer has $35,000 saved. A $665,000 loan is 95 per cent of the purchase price, with the LMI premium that implies. Adding a second security means the loan is measured against combined security, and getting $665,000 to 80 per cent requires about $831,000 of security — so a limited guarantee of roughly $131,000 over the parents’ home achieves it.

The word "limited" is doing narrower work than families assume. It caps the dollar amount the guarantor can be pursued for. It does not limit the exposure to a slice of the house: the mortgage sits over the whole property, and if the guarantee is called and not paid, the property that can be sold is the whole property. A $131,000 guarantee can put a $1.2 million family home into a forced sale.

A security guarantee, where only the guarantor’s property is used, is different from a servicing guarantee, where the guarantor’s income is also counted towards serviceability. Servicing guarantees have become much harder to obtain because they make an older person responsible for repayments they may not be able to meet in retirement. If someone has told you a parent’s income can be used, confirm precisely which product is being discussed.

The guarantor’s side of the ledger

A guarantee is a contingent liability, and it is assessed against the guarantor’s own borrowing capacity. A parent who guarantees a child’s purchase and then wants to buy an investment property, refinance, or fund a renovation will find the guaranteed amount counted against them. Guarantors who are planning their own borrowing should model both files together before signing anything.

Age matters too. Lenders scrutinise guarantees from people at or near retirement, because the plausible outcome of enforcement is a retiree losing their home, and they will ask about the guarantor’s income, assets and how the exposure ends. Some lenders decline guarantees beyond a certain age or require a documented exit.

There are process protections worth knowing about. Banks that subscribe to the Banking Code of Practice commit to giving a prospective guarantor the loan documents and specified information, warning them of what they are taking on, allowing time to consider it, not accepting a guarantee signed in the borrower’s presence, and taking reasonable steps to recover from the borrower before enforcing the guarantee. Independent legal advice is a normal requirement rather than a formality, and the guarantor’s solicitor should not be the borrower’s solicitor.

Getting out again

A guarantee is released when the loan can stand on its own: the loan-to-value ratio against the purchased property alone has to reach the lender’s threshold, commonly 80 per cent, and the remaining borrowers have to pass serviceability without the guarantee. That happens through principal repayment, through growth in the property’s value, or both.

The growth half of that plan has stopped working for now. With national values down 3.6 per cent from the March 2026 peak and falling for a fifth consecutive month in August, a release strategy that assumes the property appreciates its way to 80 per cent is a strategy without a timetable. Families should size a guarantee on the assumption that principal repayments do the work, and treat any valuation increase as a bonus.

Release also requires a fresh valuation and a formal application, not a phone call. Start it about three months before you expect to qualify, and be prepared for the answer to be that you are close rather than there.

Taking a name off a loan after a separation

There is no mechanism to simply remove a borrower from an existing loan. The practical route is a refinance into the remaining borrower’s sole name, which means that person must service the entire debt alone on current policy — at a cash rate of 4.35 per cent and a 3 percentage point assessment buffer, that is a harder test than the one the couple passed originally. Where the sole borrower cannot service the loan, the realistic options are a sale, a smaller loan with a cash adjustment, or a guarantee.

The property transfer is a separate step with its own cost. A transfer of a share between spouses or de facto partners on a relationship breakdown is exempt from duty in most Australian jurisdictions, typically where it concerns the principal place of residence and is supported by the right evidence such as a court order or a binding financial agreement. The conditions and the evidence differ by state, and the exemption is not automatic — this is a question for a family lawyer and the state revenue office, not a broker.

Where the parties are siblings or friends rather than partners, none of the relationship-breakdown exemptions apply and a transfer of a share is generally dutiable on its value.

Structure it before you apply, not after

The choices worth making deliberately: whether the second person is a borrower or a guarantor, how the title is held — joint tenancy carries survivorship, so a deceased owner’s share passes automatically to the survivor, while tenants in common allows unequal shares that pass under a will — and, for anyone buying with a sibling or a friend, a written co-ownership agreement covering who pays what, how the property is valued, how one party exits and how a dispute is resolved. That agreement is a lawyer’s document, and its absence is what turns a disagreement into litigation.

Azure Home Loans can model how each structure affects serviceability, LMI and the guarantor’s own future borrowing, and identify which lenders will accept the arrangement you want. This page is general information for Australian readers as at September 2026 and is not legal, tax or personal credit advice; the guarantee, title and duty questions here need a solicitor who has read your documents.