Introduction.
Many first-time buyers have a deposit but not quite enough income to borrow what they need.
A joint borrower sole proprietor mortgage, often shortened to JBSP, lets a close family member add their income to your application without becoming an owner of the home. You own the property in your name alone; you both share responsibility for the mortgage.
Because the family member is not on the title deeds, a JBSP mortgage can protect your first-time buyer stamp duty relief and avoid the higher rates that would apply if a homeowner bought with you.
This guide explains how JBSP works, how lenders assess it, what it means for the family member, and the alternatives worth comparing. Everyone involved should take independent legal advice before committing.
Your family member shares the mortgage, not the ownership.
01What a JBSP mortgage is.
A JBSP mortgage has two or more borrowers but only one owner. Everyone named on the mortgage is responsible for the repayments; only the owner is named on the title deeds.
Three ways family can help
| On the mortgage | On the deeds | Owns a share | |
|---|---|---|---|
| Joint mortgage | Yes | Yes | Yes |
| JBSP | Yes | No | No |
| Gifted deposit | No | No | No |
With a joint mortgage the family member becomes a co-owner. With JBSP they help with borrowing only.
Why buyers choose it
- Borrow more. A second income can increase how much you can borrow.
- Keep it yours. You own the home outright, subject to the mortgage.
- Stamp duty. You can keep first-time buyer relief and avoid the higher rates.
- Flexibility. The family member can often be removed later when your income allows.
Adviser’s note
JBSP is not offered by every lender, and criteria vary widely. Choosing the right lender matters as much as the rate.
02Who can be a joint borrower.
Lenders set their own rules on who can join a JBSP mortgage. These are the points they typically look at.
Typical lender criteria
| Point | What lenders usually require |
|---|---|
| Relationship | Close family, such as parents, grandparents or siblings; some lenders accept others |
| Number | Usually two to four borrowers in total |
| Age | The oldest borrower’s age at the end of the term, often capped between 70 and 85 |
| Occupation | Usually only the owner lives in the property |
| Loan to value | Up to 95% with some lenders |
| Legal advice | Independent legal advice for the joint borrower |
Example: Accord Mortgages allows two applicants, immediate family as the non-owner, a maximum age of 80 at the end of the term and up to 95% loan to value (published criteria, October 2026).
What lenders check on the family member
- Their income, and how secure it is
- Their own mortgage, loans and household spending
- Their credit history
- Their age, and whether their income continues into retirement
03How lenders assess affordability.
Lenders combine the incomes, then deduct everyone’s commitments. The family member’s own mortgage and spending count against the total.
An example
| Income | At 4.5 times | |
|---|---|---|
| Buyer alone | £42,000 | £189,000 |
| Parent | £58,000 | |
| Combined | £100,000 | Up to £450,000 |
Illustrative only. Income multiples vary by lender and income level, and are reduced by each borrower’s existing commitments.
Points that change the result
- The parent’s own mortgage. Its payments reduce the combined amount.
- Age and term. If the term must end by the oldest borrower’s age limit, a shorter term means higher monthly payments.
- Retirement income. Lenders may look at pension income for the years beyond retirement.
- The buyer’s income. Some lenders set a minimum income for the owner.
Adviser’s note
We model the term carefully. A slightly shorter term can make a big difference to affordability, so we compare lenders’ age limits as well as their rates.
04Stamp duty: the key advantage.
Stamp duty is paid by the people who buy the property. A JBSP borrower is not a buyer, so their own home does not trigger the higher rates.
A £400,000 first home in England
| How you buy | Stamp duty |
|---|---|
| JBSP: you own it, parent on the mortgage only | £5,000 |
| Joint purchase with a parent who owns a home | £30,000 |
| Difference | £25,000 |
England and Northern Ireland rates from 1 April 2025. First-time buyer relief: nothing up to £300,000 and 5% from £300,001 to £500,000. A joint purchase with an existing homeowner loses the relief and pays the 5% higher-rate surcharge. Scotland and Wales have their own taxes.
Other tax points
- Capital gains tax. The family member owns no share, so there is no gain for them when you sell.
- Your relief. First-time buyer relief applies only if every owner is a first-time buyer.
- Help with the deposit. A gifted deposit is separate and may have inheritance tax implications for the giver.
Saved in this example by keeping your parent off the title deeds.
05What it means for your family member.
Joining a JBSP mortgage is a serious commitment. Your family member takes on responsibility for the debt without any ownership of the home.
The commitments
- Full liability. Each borrower is responsible for the whole mortgage, not a share of it, if payments are missed.
- No ownership. They have no legal claim on the property or any increase in its value.
- Their own borrowing. Other lenders will count the JBSP mortgage when they apply for credit or a mortgage of their own.
- Credit files. Missed payments affect every borrower’s credit history.
Questions to talk through as a family
- Who pays the mortgage each month, and what happens if that changes?
- Is any money being given or lent, and is that written down?
- How will the family member be removed later?
- What happens if the owner marries, moves in with a partner or sells?
- Are wills and protection policies up to date?
Adviser’s note
The best JBSP arrangements are the ones where everyone has agreed the plan in advance, including how and when it ends.
06Protecting everyone.
A few simple steps make a JBSP arrangement safer for both the owner and the family member.
Independent legal advice
Lenders require the joint borrower to take advice from a solicitor who does not act for the owner.
Put the plan in writing
A simple family agreement records who pays, any money given or lent, and what happens on a sale.
Protection cover
Life and income protection can clear or cover the mortgage if the unexpected happens.
Review at each remortgage
When your income is high enough, the family member can usually be removed with the lender’s approval.
Removing a joint borrower
Because the title deeds do not change, removing a JBSP borrower is a mortgage change, not a property transfer. You will need to pass the lender’s affordability checks on your own.
07Alternatives to compare.
JBSP is one of several ways family can help. The right choice depends on how much help is needed and how the family wants to give it.
| Option | How it works |
|---|---|
| Gifted deposit | Family gives money towards the deposit; lenders need a gift letter |
| Joint mortgage | Family buys with you and co-owns the home |
| Family savings-backed | Family places savings with the lender as security for a smaller deposit |
| Family offset | Family savings are linked to your mortgage to reduce the interest you pay |
| Shared ownership | You buy a share and pay rent on the rest |
When JBSP tends to fit
- You have a deposit, but your income is the limit
- Your family member has steady income and room in their own budget
- Your family member already owns a home
- You want to own the property in your name
Adviser’s note
We compare these options side by side, including the cost to you and the commitment for your family.
08A JBSP purchase, illustrated.
A first-time buyer and her father
Emma earns £42,000 and has saved £40,000. On her income alone she could borrow around £189,000, short of the flats she wants.
- Purchase
- £400,000 flat, owned by Emma alone
- Joint borrower
- Her father, 56, earning £58,000 with no mortgage
- Mortgage
- £360,000 at 90% loan to value, term of 24 years to his age limit
- Stamp duty
- £5,000, rather than £30,000 if he had bought with her
- Plan
- Father took independent legal advice; review at the end of the five-year fix to remove him
This example is illustrative and does not describe a real client.
09Checklist and glossary.
Documents to have ready
- Photo ID and proof of address for every borrower
- Three months’ payslips and bank statements for each borrower
- The family member’s mortgage statement, if they have one
- Proof of your deposit and where it came from
- A gift letter for any gifted money
- Details of each borrower’s loans and credit cards
- Pension statements if a borrower is near retirement
- Contact details for both solicitors
Glossary
- JBSP
- Joint borrower sole proprietor: several borrowers, one owner.
- Proprietor
- The person named on the title deeds as owner.
- Joint borrower
- A borrower who is not an owner of the property.
- Title deeds
- The Land Registry record of who owns the property.
- Joint and several
- Each borrower is liable for the whole debt.
- Higher rates
- The 5% stamp duty surcharge on additional homes.
- Gift letter
- Confirmation that money is a gift, not a loan.
- ILA
- Independent legal advice for the joint borrower.
Related: First Time Buyers · All guides · Calculators