Joint borrower sole proprietor and family-assisted mortgages

A joint borrower sole proprietor (JBSP) mortgage lets family members help someone buy a home by adding their income to the mortgage application, without being named on the property deeds¹. The person who will live in the home is the sole proprietor, so they own all of it, while the supporting family members carry the same legal responsibility for the debt as any other borrower. Up to four people can be named on a JBSP mortgage: one or two who will own and live in the property, and up to two family members who support the application to boost the amount that can be borrowed¹.

The arrangement exists because lenders cap borrowing against income. A buyer whose salary will not stretch to the loan they need can bring in a parent's or other relative's income to pass the affordability assessment, while keeping the property in their own name. Among the bigger lenders, Barclays, Metro Bank and Clydesdale and Yorkshire have offered these deals at up to 90% loan-to-value, and Family Building Society is a specialist in the area². A related option, a family security savings account, lets family money stand behind a mortgage as security rather than income, which suits a different problem: a buyer whose income is fine but whose deposit is too small.

One owner, several borrowers: how a JBSP mortgage works

The defining feature of a JBSP mortgage is the split between the mortgage and the deeds. Every person named on the mortgage is jointly responsible for the repayments, in the same way as any joint mortgage, but only the occupying borrower or borrowers are proprietors¹. This is the opposite of an ordinary joint mortgage, where each person owns an equal share of the property and is equally responsible for the repayments regardless of whether both live there⁶.

The structure matters for two practical reasons. First, ownership: because only the child's name goes on the deeds, the parent avoids the stamp duty surcharge that would apply if they jointly bought a second property⁷. Second, responsibility: the supporting borrower is not a guarantor in the loose sense people often use. They are a full borrower, and the lender can pursue them for the whole debt if the owner cannot pay. Which? describes the arrangement as one where a parent helps their child buy a home by joining their mortgage, with only the child named on the property's deeds².

Family Building Society, the main specialist lender in this market, also offers the arrangement in reverse: adult children can support their parents' mortgage application, so the flow of help can run either way between generations¹. Joint mortgages more generally are usually shared by two people, though some lenders allow up to four borrowers to share a loan⁸, and a JBSP deal uses that same flexibility while keeping ownership with one person.

Loan sizes, deposits and income: up to 90% loan-to-value

Family Building Society states that a JBSP borrower may be able to borrow up to 90% of the property's value, depending on the loan-to-value bands of its deals¹. Its maximum loan at 90% loan-to-value on an owner-occupier capital and interest repayment basis is £500,000¹. Not every deal in the range goes that high: the society's discounted rate JBSP product XD0233 and its JBSP product XD0235 both carry a maximum loan-to-value of 80%³, and each caps the loan at £500,000³. The society's two-year and five-year fixed rate JBSP deals are the ones that reach 90% loan-to-value⁵.

The loan-to-value figure is the loan as a percentage of the property's price or valuation, and it determines the deposit: the lower the loan-to-value a lender will accept, the bigger the deposit the buyer must put down. The general guide to loan to value explains how the ratio is worked out and why it affects both the deals available and their cost. For comparison, buy-to-let mortgages usually require at least a 20% deposit, meaning a maximum loan-to-value of 80%¹¹.

What the income of each borrower buys also depends on how the lender assesses it. For self-employed supporters, mortgage lenders will look at their individual share of the profits rather than a business's headline figures¹². The point of adding a supporter is to raise the combined income the lender will consider, so the supporter's earnings, outgoings and existing debts all feed the affordability calculation alongside the owner's. The guide to how much can I borrow covers how lenders turn income into a loan figure.

Repayment, interest-only and remortgage rules

JBSP mortgages come in both repayment and interest-only forms, and Family Building Society's range includes both. Its two-year fixed rate deal is offered in a repayment version⁸ and an interest-only version¹⁰, and its five-year fixed rate deal is offered on a repayment basis⁹. The society's discounted rate JBSP product XD0235 is an interest-only mortgage with a maximum loan-to-value of 80%⁴. All of these products are available for purchase and remortgage applications³.

The difference between the two forms is the same as on any mortgage. With a repayment mortgage the monthly payment covers interest and a slice of the capital, so the debt is cleared by the end of the term. With an interest-only mortgage, borrowers just repay the interest on the loan, and the full amount borrowed is still owed at the end of the term¹³. Macmillan puts the risk plainly: at the end of the term, you still owe the full amount of capital you borrowed¹⁴.

Because of that, interest-only is regulated more tightly. Under the FCA's mortgage rules, a lender may only enter into an interest-only mortgage, or switch a repayment mortgage onto an interest-only basis, if it has evidence that the customer will have in place a clearly understood and credible repayment strategy with the potential to repay the capital borrowed and any interest reasonably expected to accrue¹⁵. This rule came out of the Mortgage Market Review, which allowed interest-only borrowing only where there is a credible repayment strategy in place¹⁶. The guides to repayment mortgages, interest-only mortgages and the repayment strategies lenders accept cover this in detail.

A related product, the retirement interest-only mortgage, is defined in the FCA Handbook as an interest-only mortgage requiring the interest to be repaid in full over the stated term, restricted to older customers above a specified age, under which the lender cannot seek full repayment until specified life events such as death or going into care¹⁷. Which? describes the practical effect: you pay interest each month, with the capital repaid when the property is sold, either on death or on going into care¹⁸. This can matter for JBSP arrangements where a parent is a supporting borrower near or in retirement, since the lender will look at how the mortgage is repaid across the whole term, and research by Which? has found that over half of borrowers will still have a mortgage at 65¹⁸.

Who pays the monthly bill

The rule Family Building Society sets is straightforward: the monthly mortgage payment has to come from a bank account in the name of at least one of the borrowers, but it does not have to be the occupying borrower³. So the owner can pay the mortgage from their own account, a supporting parent can pay it from theirs, or the two can divide the payments between them, as long as each payment comes from a named borrower's account.

This flexibility is useful where the arrangement is genuinely shared, but it does not change where legal responsibility sits. Every borrower is liable for the full monthly payment, not just a share of it, so if the owner pays nothing and the supporter pays everything, the supporter has no claim against the owner beyond whatever private agreement the family has. Any private arrangement about who pays what is a family matter, not a mortgage term, and it is worth writing down.

Buy to let and other property types

JBSP mortgages are not limited to homes the buyer will live in. Family Building Society's brochure states that in buy-to-let cases there will be one owning borrower and one non-owning borrower, and that for a buy-to-let property the owner can also get support from spouse or partners³. The structure is the same: the supporter's income strengthens the application while the property stays in the owner's name alone.

The lending limits differ, as they do across the buy-to-let market. Buy-to-let mortgages usually require at least a 20% deposit, meaning a maximum loan-to-value of 80%¹¹, which is lower than the up to 90% loan-to-value the society states may be available on its JBSP mortgages¹. Buy-to-let lending is also assessed on the rent the property is expected to generate rather than purely on income, so a supporter's role in that market is narrower. The guide to buy-to-let mortgages covers how these loans work and how they differ from residential lending.

Stamp Duty and the other costs of buying

The Stamp Duty position is one of the strongest arguments for a JBSP structure. Family Building Society states that the joint borrowers will not be liable for stamp duty since they will not own any part of the property, as the purchaser remains the sole proprietor¹. Compare this with the ordinary joint mortgage route: a parent who already owns their own home and goes on the deeds with their child will need to pay the second property stamp duty surcharge, which can run to thousands of pounds⁷. Which? makes the same point for parents helping generally: on a joint mortgage you are jointly responsible for the payments and will need to pay second property stamp duty rates if you already own a home¹⁹.

Stamp Duty is only one of the one-off costs of buying. NI Direct lists the others to budget for: a solicitor, an independent surveyor, the mortgage arrangement fee, the Land Registry fee and Stamp Duty itself²⁰. Shelter Cymru gives the same warning for joint buyers: budget for the one-off costs of buying a property, such as administration and solicitor fees and Stamp Duty²¹. In a JBSP purchase the supporting borrower may also want their own legal advice, which is an additional cost the family should expect.

Family security savings: help without adding income

Not every family problem is income. Where a buyer earns enough but lacks a deposit, a family security savings account offers a different route: family money is held by the lender as security behind the mortgage instead of, or alongside, a cash deposit. Family Building Society's Family Security Account works this way, linked to what the society calls a Family Mortgage.

The account's terms show how restricted it is. It can only be applied for by post, additions are not permitted, and withdrawals or account closure are only available following a review of the linked Family Mortgage²². Interest is calculated daily and paid annually on 31 December, available from the following day, and is paid gross without deduction of income tax; there is no monthly interest option²². The rate is variable and may be changed²². The society's illustration shows a projected gross balance of £1,030.50 from a £1,000 opening balance over 12 months, with no additions or withdrawals²³. The account is not currently available to new customers²².

The savings remain the family's money, and as a deposit with an authorised UK building society they carry FSCS protection like any other savings account, which the society confirms²². The protection limits are covered in the final section of this page.

Applying: lender checks and independent legal advice

JBSP mortgages are a niche product. Only a small number of lenders offer them, so the first practical step is finding one, and a mortgage broker can identify which lenders accept these applications at any given time. Among the big players, only Barclays, Metro Bank and Clydesdale and Yorkshire have offered these deals, at up to 90% loan-to-value², and Family Building Society is the specialist lender in the market¹.

Once a lender is found, the checks are the same in kind as any mortgage, applied to every borrower. Lenders will run a credit check on each applicant before granting a mortgage, and if one party has a poor credit score, it could impact the lender's decision²⁴. A missed mortgage payment will show up on both credit reports, regardless of whose fault it was²⁵. Income is assessed for each borrower, including each partner's individual share of profits where a supporter is self-employed¹². Which? also notes that lenders are more likely to approve a JBSP application if the child can show likely significant wage growth, along with the overall financial stability of the parent².

Legal advice is the step that protects the supporting borrower. Because they are taking on full liability for a debt on a property they will not own, they need to understand exactly what they are signing. StepChange's guidance on joint mortgages and separation is blunt: get legal advice if you have a joint mortgage²⁷. National Debtline says the same, and adds the warning that matters most here: it is unlikely that a mortgage lender will remove someone's name from a mortgage unless they are happy the other person can afford the repayments²⁸. A supporter should go into the application expecting that the commitment may last for years.

Risks for the owner and for the supporting borrower

The risks sit mostly with the supporting borrower, and they are substantial. The supporter is fully liable for the mortgage debt, including the whole of any shortfall, yet owns none of the property. If the owner stops paying, the lender can pursue the supporter for everything, and a missed payment damages both parties' credit files regardless of whose fault it was²⁵. If the relationship breaks down, parents could find it difficult to have their names removed from the mortgage agreement if relations sour², and a lender will not remove a name unless satisfied the remaining borrower can afford the repayments alone²⁸.

The supporter's own borrowing is affected too. Because they are legally responsible for the JBSP mortgage payments, the commitment counts against them if they later want to borrow for themselves, and they are jointly responsible for the payments in the meantime¹⁹. Their ability to remortgage their own home, borrow for another purchase or retire with a clear credit position can all be shaped by an arrangement entered into to help someone else.

The owner carries risks as well. The property is theirs alone, but so is the practical burden of the payments, and if they cannot pay, the consequences reach the whole family. Interest-only JBSP deals add the standard interest-only risk: at the end of the term, the full capital is still owed¹⁴, and the FCA requires a credible repayment strategy before such a mortgage can be granted¹⁵. Where a relationship behind the arrangement breaks down, guidance from Shelter Cymru on relationship breakdown applies: joint owners and joint borrowers need to sort both the property and the debt, and benefits rules can interact with mortgage costs for joint or sole owners claiming Income Support, income-based Jobseeker's Allowance or Pension Credit²⁹. Support for Mortgage Interest, where it applies, is paid monthly directly to the mortgage provider³⁰, and for joint claimants both members of the claim must sign both the loan agreement and the charge form³¹.

Where protection applies and where it stops

Two kinds of protection are relevant to family-assisted mortgages, and each has limits.

The first is deposit protection for family savings held as security. Money in a family security savings account is a deposit like any other, and FSCS protects up to £120,000 per eligible person, in total across all accounts they hold with the same authorised firm⁵. Joint accounts are eligible for the same protection per person, so a joint account with two holders is protected up to £240,000⁴. The Bank of England gives the same figure: a joint account with two holders would be protected up to £240,000³³. One limit to watch: if the family has money in multiple accounts with banks that are part of the same banking group and share a banking licence, those accounts are treated as one bank, with the £120,000 limit applying across all of them³². FSCS can only protect money held by UK branches of authorised banks and building societies³⁴.

The second is protection over the mortgage itself. FSCS protects mortgage advice³⁵, which matters if the arrangement was recommended by an adviser who then failed. It does not protect a family against the risks they have taken on voluntarily: a supporter who becomes liable for payments they did not expect, or who cannot exit the mortgage, has no compensation route for that. The FSCS's own research lists what it covers, including deposits, insurance policies, some investments, insurance broking and mortgage advice³⁶, and its protection checker lets a family confirm cover for a specific firm³⁴.

For complaints about how a JBSP mortgage was sold or administered, the Financial Ombudsman can look at a complaint against a lender or adviser without charge, and the guide to mortgage rules and your rights sets out what lenders must do. But the core protections a family needs here are the ones they build themselves: independent legal advice for the supporting borrower before completion, a written family agreement on who pays what, and a clear understanding that only the owner's name goes on the deeds while every borrower's name stays on the debt.