Joint Borrower Sole Proprietor Mortgages: JBSP vs Guarantor Options
Updated 12 July 2026
A joint borrower sole proprietor mortgage (JBSP) lets a family member join your mortgage application to increase borrowing power, without being named on the property title deeds. The main buyer keeps sole ownership of the home while the supporting borrower’s income helps meet the lender’s affordability requirements. It is one of the most practical routes for first-time buyers and home movers who need family support to bridge an affordability gap. Mortgage One arranges JBSP mortgages with lenders from the whole of market and can explain how this structure could work for your purchase.
To discuss whether a JBSP mortgage could work for your situation, call 01202 155992 or contact Mortgage One.
How a joint borrower sole proprietor mortgage works
A joint borrower sole proprietor (JBSP) mortgage puts up to four people on the loan while only the main buyer goes on the title deeds. Every borrower’s income can count towards affordability, so a parent can lift the maximum loan without owning any share of the property.
With a JBSP mortgage, two or more people are named on the mortgage application and loan agreement, but only the main borrower appears on the property title deeds. The supporting borrower, typically a parent or close family member, adds their income to the affordability assessment. This can increase the amount the main borrower is able to borrow without the supporting party acquiring any ownership interest in the property.
Most lenders offering JBSP products allow up to four borrowers on the application. Income from all borrowers can usually be used in the affordability calculation, though some lenders weight the additional incomes differently. The mortgage term is often restricted by the age of the oldest borrower at the end of the term, which can shorten the maximum term where an older parent joins the application.
What is a guarantor mortgage and how does it work?
A guarantor mortgage lets a family member guarantee your repayments by securing their own savings or home equity against the loan, without joining the mortgage or the deeds. Savings-backed versions typically hold 5% to 20% of the property value with the lender until the balance falls.
A guarantor mortgage is the arrangement most parents remember from before JBSP became widespread. The guarantor, usually a parent, signs a legal agreement to cover the mortgage payments if the borrower cannot. They are not a borrower on the loan, their income is used to show they could cover the payments rather than to increase the loan itself, and they never appear on the title deeds.
The guarantee is backed by security. With savings as security, the guarantor deposits a lump sum into an account held with the lender until the mortgage balance or loan-to-value falls to an agreed level. With property as security, the lender takes a legal charge over equity in the guarantor’s own home, which usually needs to be owned outright or close to it.
True guarantor products have become less common because many lenders now prefer the JBSP structure, which is why most people searching for a guarantor mortgage today end up arranging a JBSP mortgage instead. For the version of this comparison written for guarantor searchers, see the guarantor mortgage guide.
JBSP mortgage vs guarantor mortgage: the key differences
The core difference is liability and income. On a JBSP mortgage every borrower is fully liable and every income counts towards the loan. A guarantor only steps in if payments are missed, their income is not used for affordability, and their savings or property sit as security instead.
All borrowers on a JBSP mortgage are jointly and severally liable for the repayments. If the main borrower misses a payment, the lender can pursue any borrower on the agreement. This shared liability is what distinguishes JBSP from a traditional guarantor mortgage, where the guarantor’s role was typically limited to covering shortfalls rather than being a full borrower.
In practice, the differences show up in four places:
• Income: a JBSP application counts every borrower’s income towards the loan. A guarantee reassures the lender but does not raise the borrowing figure in the same way
• Security: JBSP is secured on the property being bought. A guarantor mortgage adds the guarantor’s savings or home equity as extra security
• Credit files: both structures put the commitment on the supporting party’s record, and missed payments affect everyone involved
• Product choice: far more lenders offer JBSP, and JBSP mortgage rates are usually drawn from the lender’s standard residential range, priced by loan-to-value and product term rather than by the structure itself
Who can use a JBSP mortgage to boost affordability
JBSP mortgages suit first-time buyers and home movers whose income falls short of the loan they need, with a parent or close family member willing to join the application. The supporting borrower does not need to live in the property and takes no ownership stake.
JBSP mortgages are primarily designed for residential purchases where the main borrower will live in the property. They are most commonly used by:
• First-time buyers whose income alone does not meet the lender’s affordability threshold
• Home movers who need additional income support to step up to a larger property
• Young professionals with career earnings potential but a current salary that limits borrowing
• Families who want to support a purchase without the supporting party becoming a property owner
The supporting borrower does not need to live in the property. Their role is to strengthen the affordability position. Some lenders also accept non-family members as supporting borrowers, though criteria vary. For first-time buyers exploring their deposit and affordability options, the first-time buyer mortgage guide and the mortgage deposits guide cover the wider picture.
JBSP is not typically available for buy-to-let purchases. It is designed for owner-occupied residential mortgages, though some lenders may consider it for specific scenarios such as remortgaging.
Stamp duty rules for JBSP and guarantor mortgages
Because the supporting borrower or guarantor never goes on the title deeds, they are not treated as buying the property. A first-time buyer keeps their stamp duty relief of 0% on the first £300,000, and a parent who owns a home does not trigger the 5% additional property surcharge.
One of the practical advantages of a JBSP structure is its treatment for Stamp Duty Land Tax purposes. Because the supporting borrower is not named on the property title deeds, they are not treated as purchasing the property. This means:
• A first-time buyer using JBSP can still qualify for first-time buyer stamp duty relief, even if the supporting parent already owns a property. First-time buyer relief currently means no SDLT on the first £300,000 of the purchase price for properties up to £500,000
• The supporting borrower who already owns another property does not trigger the 5% higher rate SDLT surcharge that would apply if they were named on the deeds as a joint owner
The same logic applies to a guarantor, who never appears on the deeds either. This is a significant difference compared to a standard joint mortgage, where adding a parent who already owns property would typically forfeit first-time buyer relief and trigger the surcharge. However, stamp duty rules are complex and individual circumstances vary. Buyers should always take legal advice from their conveyancer on SDLT liability before proceeding. Use the Mortgage One stamp duty calculator for an estimate of what you may owe.
If a parent who already owns property is helping you buy and you want to keep first-time buyer relief intact, call 01202 155992 or contact Mortgage One.
Which lenders offer JBSP mortgages and what do they require?
Several high street banks and building societies offer JBSP lending, often under their own family assist branding, with deposits from 5% and up to 95% loan-to-value available. Classic guarantor products are now rare, so most guarantor enquiries end up placed as JBSP cases.
JBSP is now a mainstream structure rather than a niche one, but lenders rarely use the same name for it, so you will not always see the letters JBSP on a lender’s website. A smaller group of building societies still offer savings-backed family security products in place of a classic guarantee. Because the branding varies and criteria change, a whole of market search is the practical way to find which lenders fit a specific case. Common criteria include:
• Deposit: criteria mirror standard residential lending, with some lenders going to the top of their loan-to-value range on JBSP applications
• Income: all borrowers’ incomes are assessed. Lenders typically apply income multiples to the combined earnings, though some weight the highest earner’s income more heavily. The income multiples guide explains how lenders set these caps
• Credit history: all borrowers undergo a full credit check. Any adverse credit on a supporting borrower’s record can affect the application. For guidance on what lenders look for, see the mortgage credit checks guide
• Age: many lenders cap the mortgage term by the oldest borrower’s age at the end of the term, and some extend further where retirement income can be evidenced
• Independent legal advice: lenders typically require each non-proprietor borrower to receive independent legal advice before the mortgage completes. This must come from a separate solicitor to the one handling the property transaction
• Relationship: some lenders restrict JBSP to family members, while others accept friends or other third parties
Mortgage One has access to JBSP products from lenders from the whole of market and can match your circumstances to the right criteria. For a broader look at how lenders assess mortgage applications, the mortgage affordability guide explains the process.
Risks for supporting borrowers and how to exit later
A supporting borrower is liable for the full mortgage, the loan sits on their credit file, and they build no equity in return. Most families plan an exit: remortgaging into the main borrower’s sole name once their income supports the loan, or removal at the end of the initial deal.
A JBSP mortgage creates real financial obligations for the supporting borrower, even though they have no ownership interest in the property. The same applies to a guarantor whose savings or home stand behind the loan. Before agreeing to either arrangement, all parties should understand:
• The mortgage will appear on the supporting borrower’s credit file for as long as they remain on the agreement. This may reduce their own borrowing capacity if they apply for credit or a mortgage of their own while the arrangement runs
• If any payment is missed or late, it will be recorded on every borrower’s credit report
• The supporting borrower has no legal claim to the property, no share of any equity growth, and no right to sell the property
• If the main borrower cannot make repayments, the lender can pursue the supporting borrower for the full amount owed
• All parties should consider whether mortgage payment protection or income protection insurance is appropriate
These obligations are one reason independent legal advice is a standard lender requirement. Both the main borrower and the supporting borrower should be clear on the terms before proceeding.
Removing a supporting borrower or guarantor later
JBSP is often intended as a temporary arrangement. Once the main borrower’s income has increased, or enough of the mortgage has been repaid, it may be possible to remove the supporting borrower. This is usually done by remortgaging into a sole application, subject to passing the lender’s affordability assessment on the main borrower’s income alone. The remortgaging guide explains how the process works.
Some lenders also allow a supporting borrower to be removed at the end of the initial product term without a full remortgage, provided the remaining borrower meets affordability criteria. Timing this around the end of a fixed-rate period can avoid early repayment charges. Guarantors are released in a similar way, once the balance or loan-to-value reaches the level agreed at the outset.
Planning an exit route from the outset is sensible. Mortgage One can advise on structuring the arrangement so that removing the supporting borrower is as straightforward as possible when the time comes.
For a free initial consultation on JBSP and guarantor mortgage options, call 01202 155992 or contact Mortgage One.
The information provided in this article is for general guidance only and does not constitute personal or regulated financial advice. If you’d like to understand what these moves could mean for you, speak to Mortgage One. We can explain your options and timings based on your specific circumstances.
FAQs
1. What is a joint borrower sole proprietor mortgage?
A JBSP mortgage allows two or more people to be named on the mortgage while only the main borrower appears on the property title deeds and legally owns the home. The supporting borrower’s income boosts affordability without them becoming a property owner.
2. How is a JBSP mortgage different from a guarantor mortgage?
With a guarantor mortgage, the guarantor agrees to cover payments if the borrower defaults and secures that promise with savings or home equity, but their income does not increase the loan. With a JBSP mortgage, the supporting party is a full joint borrower whose income is assessed for affordability, and all borrowers share liability for repayments.
3. Do guarantor mortgages still exist in the UK?
A small number of lenders still offer guarantee-style or savings-backed family security products, but most have replaced them with JBSP lending. In practice, the majority of guarantor mortgage enquiries are now placed as JBSP cases.
4. Who can be a guarantor or supporting borrower?
Lenders usually expect a close family member, most often a parent, with a clean credit record and enough income or equity to stand behind the commitment. Some JBSP lenders also accept wider family or friends, and retired supporters can qualify where pension income can be evidenced.
5. Can I still get first-time buyer stamp duty relief with a JBSP mortgage?
In most cases, yes. Because the supporting borrower is not named on the title deeds, first-time buyer relief is assessed on the sole proprietor’s status. Take legal advice from your conveyancer to confirm your position.
6. What are the disadvantages of a JBSP mortgage?
The supporting borrower takes on full liability for a property they do not own, the commitment sits on their credit file, and the mortgage term may be shortened by their age. Removing them later depends on the main borrower passing affordability alone, which is never guaranteed.
7. Will being a supporting borrower or guarantor affect my own mortgage?
Yes. Lenders treat the commitment as an existing liability, so it can reduce what you can borrow on your own mortgage or remortgage while the arrangement is in place. Missed payments by the main borrower would also appear on your credit file.
8. Do I need a mortgage broker for a JBSP or guarantor mortgage?
You can apply directly, but lender branding, criteria and age rules vary widely, and not every lender offers the structure. A whole of market broker can identify which lenders fit the family’s income, age and deposit profile and structure the case so a later exit is realistic.