Complete Guide to Joint Borrower Sole Proprietor Mortgages in the UK (2025 Edition)

Buying property in the UK is expensive, and affordability checks often block first-time buyers or those with limited income. A Joint Borrower Sole Proprietor (JBSP) mortgage can provide a solution.

With a JBSP mortgage, a parent, partner, or relative can join your mortgage application to boost borrowing power — but they won’t be named on the property deeds. This avoids extra Stamp Duty Land Tax (SDLT) charges while still giving you the support you need.

In this guide, we’ll explain how JBSP mortgages work, who can use them, lender requirements, benefits, risks, and alternatives in 2025.

Key Takeaways: JBSP Mortgages

• A JBSP mortgage allows multiple people on the mortgage, but only one on the property title.
• It boosts affordability without triggering SDLT second home surcharges for parents/relatives.
• All borrowers share responsibility for repayments.
• Popular with first-time buyers, parents helping children, or couples with uneven credit profiles.
• Lender criteria include credit checks, income assessment, age limits, and residency status.
• Alternatives include guarantor mortgages, joint ownership, and shared ownership schemes.

What Is a Joint Borrower Sole Proprietor Mortgage in the UK?

A Joint Borrower Sole Proprietor mortgage is a product where:

• Borrowers: Two or more people are responsible for repaying the loan.
• Proprietor: Only one borrower is on the property deeds and is the legal owner.

This setup boosts borrowing power while keeping ownership (and tax liability) simple.

How Does a JBSP Mortgage Work in the UK?

Here’s how JBSP mortgages typically operate:

1. A buyer applies for a mortgage but falls short on affordability.
2. A parent or relative joins as a joint borrower.
3. The lender combines both incomes for affordability checks.
4. The supporter is not added to the property deeds.
5. Ownership remains solely with the main proprietor.

This arrangement allows families to support buyers without triggering extra tax or co-ownership complications.

Eligibility Checklist: Do You Qualify for a JBSP Mortgage?

You may be eligible if you:

• Are a UK resident buyer needing additional affordability support.
• Have a parent, relative, or partner willing to act as a joint borrower.
• Can provide a deposit of 5–15% (varies by lender).
• Have good credit history across all borrowers.
• Ensure the supporting borrower is within age limits (typically mortgage must end before 70–80).

Real-World Example of a JBSP Mortgage

At WIS Mortgages, we recently helped parents secure a JBSP mortgage for their son, aged 19, starting university in London.

• Parents’ contractor income was used for affordability.
• The son was named as sole proprietor, avoiding SDLT surcharges.
• Instead of paying rent, he lived in his own property, supported by his parents’ income.

This arrangement allowed the son to own property in his name, while the parents avoided higher tax charges.

Who Can Get a Joint Borrower Sole Proprietor Mortgage?

A JBSP mortgage is best suited for:

• First-time buyers needing support from parents.
• Couples where one has poor credit but the other can support affordability.
• Parents and relatives helping without wanting ownership.
• Older relatives supporting buyers without complicating inheritance.

Benefits of JBSP Mortgages

• Boosts borrowing power by combining incomes.
• Preserves sole ownership — only one name on deeds.
• SDLT savings — avoids second home surcharges.
• Flexible support — parents/relatives can help without co-owning.
• Credit building — sole proprietor strengthens profile through repayments.

Risks of JBSP Mortgages

• All borrowers are liable if repayments are missed.
• Future borrowing limits for supporting relatives.
• Age restrictions may exclude older parents.
• Relationship risks if disputes arise.
• Limited lender pool compared with standard mortgages.

JBSP Mortgage Lender Criteria and Eligibility (UK 2025)

Each lender sets their own rules, but typical criteria include:

• Credit checks on all borrowers.
• Income assessment including salaries, bonuses, and allowances.
• Maximum borrowers: Usually up to four.
• Age limits: Mortgage must end by age 70–80 of the oldest borrower.
• Residency: UK residency is often required for all applicants.

Specialist JBSP mortgage lenders may allow flexibility for complex cases.

Comparison: JBSP vs Other Mortgage Options

Step-by-Step: How to Apply for a JBSP Mortgage

1. Check eligibility (credit scores, income, age limits).
2. Confirm affordability with combined incomes.
3. Select a lender offering JBSP products (via broker).
4. Legal checks — all borrowers receive independent advice.
5. Submit application with documents for all borrowers.
6. Mortgage offer issued, with proprietor named on deeds only.

Tax and Legal Considerations

• Stamp Duty: Supporting borrowers not on deeds avoid SDLT surcharges.
• Inheritance tax: Parents not listed as owners simplifies planning.
• Capital Gains Tax: Only the proprietor is liable on sale.
• Legal advice: Independent advice is usually required for all borrowers.

FAQs About JBSP Mortgages

Which lenders offer JBSP mortgages in the UK?

A mix of high-street banks and specialist lenders — a broker can match you to the right one.

Do JBSP mortgages affect Stamp Duty?

Yes — they help avoid second home SDLT surcharges for parents or relatives.

Can a JBSP mortgage help first-time buyers?

Absolutely. It’s one of the most common uses, allowing parental support without co-ownership.

What deposit do I need for a JBSP mortgage?

Typically 5–15%, depending on the lender and borrower profile.

Can more than two people be on a JBSP mortgage?

Yes, usually up to four borrowers can be named, depending on lender rules.

Is a JBSP Mortgage Right for You?

A Joint Borrower Sole Proprietor mortgage can be the perfect solution if you need extra affordability support but want to keep ownership simple. It allows family or partners to help without adding complexity around tax or property ownership.

At WIS Mortgages, we specialise in helping clients secure JBSP mortgages with lenders who understand these arrangements.

Get in touch with WIS Mortgages today to explore your JBSP mortgage options in 2025.

Important

Your home may be repossessed if you do not keep up with repayments on your mortgage.

This article is for general information only and does not constitute financial advice. Always speak to an FCA-authorised adviser before making financial decisions. Product availability and criteria are subject to change. Accurate as of September 2025.