Joint Borrower Sole Proprietor Mortgages

A joint borrower sole proprietor mortgage, commonly known as a JBSP mortgage, allows two or more people to be responsible for a mortgage while fewer of them legally own the property.

For example, a parent could join their son or daughter’s mortgage application and have their income considered for affordability, without becoming a legal owner of the property.

This can make a Joint Borrower Sole Proprietor (JBSP) mortgage particularly useful for first-time buyers and other borrowers who have enough deposit to purchase a property but cannot borrow the mortgage amount they need based on their income alone.

Unlike a traditional guarantor arrangement, the supporting borrower is normally jointly responsible for the mortgage debt from the outset.

Quick Answer

A joint borrower sole proprietor mortgage allows multiple borrowers’ incomes to be considered for a mortgage while only the proprietor or proprietors are named as legal owners of the property.

All borrowers are responsible for the mortgage repayments, but the supporting joint borrower does not automatically acquire ownership of the home.

One common example is a parent joining their adult child on the mortgage to increase borrowing capacity while the child remains the sole proprietor.

If you want an initial indication of what you might be able to borrow, try our Joint Borrower Sole Proprietor Mortgage Calculator.

How Does A Joint Borrower Sole Proprietor Mortgage Work?

With a standard joint mortgage, the people named on the mortgage will typically also own the property.

A joint borrower sole proprietor mortgage separates mortgage responsibility from property ownership.

For example:
Buyer: £50,000 income
Parent: £70,000 income
Combined income considered: £120,000
Property owner: Buyer only
Mortgage borrowers: Buyer + parent

Rather than assessing affordability solely against the buyer’s £50,000 income, a suitable JBSP lender may be able to consider income from both applicants.

The exact amount available will depend on the lender’s affordability assessment, debts, financial commitments, deposit, ages of the applicants and other criteria. It should not simply be assumed that the lender will multiply the combined £120,000 income by a particular figure.

Both people would be named on the mortgage and responsible for the debt, but only the buyer would be named as the proprietor in this example.

Who Is A Joint Borrower Sole Proprietor Mortgage For?

Although joint borrower sole proprietor mortgages are often associated with parents helping first-time buyers, they can potentially be useful in several situations.

They may be considered where:

• A first-time buyer’s income isn’t sufficient for the mortgage they need
• Parents want to support an adult child without jointly owning their home
• One partner wants to help with mortgage affordability without being named as an owner
• Family members want to combine incomes for affordability purposes
• An adult child wants to help a parent with mortgage affordability

The rules aren’t identical across lenders. Some restrict who can act as the supporting borrower, while others can be more flexible.

For example, Barclays’ current Mortgage Boost proposition allows income from someone such as a parent, relative or friend to support the mortgage while they remain off the property ownership. Skipton’s published JBSP criteria also state that it has no relationship restriction between the main and supporting borrowers, subject to its wider criteria.

How Much Can I Borrow With A Joint Borrower Sole Proprietor Mortgage?

One of the main reasons borrowers consider a joint borrower sole proprietor mortgage is to increase their potential borrowing.

Mortgage lenders normally assess affordability using a combination of income and expenditure. If a buyer cannot borrow enough using their income alone, adding an eligible supporting borrower may allow additional income to be included in the affordability assessment.

However, the supporting borrower’s income isn’t considered in isolation.

A lender may also assess their:

• Existing mortgage or housing costs
• Loans and credit commitments
• Dependants
• Regular expenditure
• Age and intended mortgage term
• Credit history
• Other financial commitments

This is particularly important when parents support their children. A parent earning a high income doesn’t necessarily mean that the whole income can simply be used to increase the child’s borrowing.

Want to see what the figures could look like? Use Oportfolio’s Joint Borrower Sole Proprietor Mortgage Calculator for an initial estimate.

Which Banks Offer Joint Borrower Sole Proprietor Mortgages?

A common question is which banks offer joint borrower sole proprietor mortgages in the UK?

A number of banks and building societies currently offer JBSP arrangements or products that operate on a similar basis. Examples include Barclays, Metro Bank and Skipton Building Society, although individual lenders use different product names and eligibility criteria.

For example, Barclays calls its proposition Mortgage Boost, while Metro Bank specifically offers Joint Borrower Sole Proprietor lending. Metro Bank expanded its proposition in July 2026 with a JBSP product capable of lending above 95% and up to 100% of the property’s value for qualifying applicants with an eligible immediate family member supporting them. Specific eligibility requirements apply.

The important point is that joint borrower sole proprietor mortgage lenders don’t all use the same criteria.

Differences can include:

• Who can act as the supporting borrower
• How many applicants are allowed
• Maximum loan-to-value
• Maximum mortgage term
• Age restrictions
• How affordability is calculated
• Acceptable income types
• Whether the supporting borrower can live in the property
• Independent legal advice requirements

This is why searching for “who does joint borrower sole proprietor mortgages?” is only part of the process. The more important question is which JBSP lender is appropriate for your particular circumstances? And that is where getting help from an experienced and qualified mortgage adviser can be particularly valuable.

Do Joint Borrower Sole Proprietor Mortgages Avoid Additional Stamp Duty?

This is one of the most important potential advantages of a JBSP structure, but it needs to be understood correctly. With a joint borrower sole proprietor mortgage, the supporting borrower isn’t necessarily a legal owner of the property. That can be particularly relevant where a parent helping their child already owns their own home.

If the parent were also purchasing an interest in the child’s property, their existing property ownership could have property tax implications. In England and Northern Ireland, for example, this could affect the Stamp Duty Land Tax (SDLT) position.

The mortgage arrangement itself does not determine the tax due. Stamp duty depends on the purchasers, property ownership and individual circumstances, so appropriate tax and legal advice should be obtained.

This distinction is one reason joint borrower sole proprietor mortgages UK have become an increasingly important form of family-assisted borrowing.

Does The Supporting Borrower Own Any Of The Property?

No, not simply because they are named on a joint borrower sole proprietor mortgage.

The defining feature of a JBSP mortgage is that someone can be a borrower without also being a proprietor.

That means the supporting borrower can be legally responsible for repaying the mortgage without automatically having a legal ownership share in the property. This is a significant commitment and one that both parties need to understand before proceeding.

Do You Need Independent Legal Advice For A Joint Borrower Sole Proprietor Mortgage?

Some lenders require the supporting borrower to obtain independent legal advice before completing a joint borrower sole proprietor mortgage.

This helps make sure they understand the implications of being legally responsible for the mortgage without necessarily owning any of the property. Requirements vary between lenders, so this should be checked as part of the mortgage application.

Is The Supporting Borrower Responsible For The Whole Mortgage?

Potentially, yes. Being a supporting borrower isn’t the same as simply allowing a lender to look at your salary. Everyone named as a borrower can be legally responsible for the mortgage repayments.

If payments aren’t maintained, this can potentially affect all borrowers and their credit records. Barclays, for example, explicitly states that everyone named on its Mortgage Boost mortgage is legally responsible for payments.

Parents or other family members therefore need to consider the commitment carefully before using their income to support somebody else’s mortgage.

What Are The Advantages Of A Joint Borrower Sole Proprietor Mortgage?

For the right borrower, potential advantages include:

• Using another person’s income to support mortgage affordability
• Potentially increasing the amount available to borrow
• Allowing the main buyer to retain ownership of the property
• Helping first-time buyers access the property market
• Giving parents a way to support children without necessarily owning part of their home
• Potential stamp duty advantages compared with some joint-ownership structures

However, a JBSP mortgage shouldn’t be viewed simply as a way to maximise borrowing. All borrowers need to be comfortable with the mortgage commitment.

What Are The Disadvantages Of A JBSP Mortgage?

There are important considerations too. The supporting borrower takes on responsibility for a potentially substantial debt without necessarily owning any of the property. Their involvement could also affect their ability to borrow elsewhere because lenders may take the JBSP mortgage commitment into account when assessing future applications.

Other considerations can include:

• Independent legal advice costs
• Age affecting the available mortgage term
• Fewer lender options than conventional mortgages
• Affordability assessments covering multiple households
• Difficulty removing the supporting borrower if the proprietor cannot later afford the mortgage alone
• Potential impact of missed payments on all borrowers

The benefits therefore need to be weighed against the long-term financial commitment.

Real Joint Borrower Sole Proprietor Mortgage Case Study

We’ve previously helped clients where a conventional mortgage didn’t provide the borrowing they needed, but a JBSP structure allowed family income to be considered while keeping the property ownership appropriately structured.

You can read the full Joint Borrower Sole Proprietor Mortgage Case Study to see how this type of mortgage can work in practice.

Oportfolio Insight

The most important thing to understand about a joint borrower sole proprietor (JBSP) mortgage is that it isn’t simply a way to “add Mum or Dad’s salary” to a mortgage application. The supporting borrower’s age, existing mortgage, expenditure, credit commitments and wider financial circumstances can all affect affordability.

Two lenders looking at exactly the same family could therefore produce very different borrowing figures. That’s where lender selection becomes important. The question isn’t simply whether a lender offers JBSP mortgages, but whether its affordability model and criteria work for the circumstances of everyone involved.

Is A Joint Borrower Sole Proprietor Mortgage Right For You?

A joint borrower sole proprietor mortgage can provide an alternative route to homeownership where one person’s income isn’t sufficient to secure the mortgage they need. However, it creates a significant financial commitment for everyone named on the mortgage.

At Oportfolio Mortgages, we can assess the income and circumstances of the buyer and supporting borrower, compare suitable joint borrower sole proprietor mortgage lenders, and establish which options may be appropriate.

Start by using our Joint Borrower Sole Proprietor Mortgage Calculator or speak to an Oportfolio mortgage adviser about your circumstances.

FAQ: Joint Borrower Sole Proprietor Mortgages