Joint Borrower, Sole Proprietor Mortgages: Who They’re For & When They Work

November 19th 2025

If you’re struggling with affordability on your own, you might have come across something called a Joint Borrower, Sole Proprietor (JBSP) mortgage. It’s a mouthful, but the idea is simple: someone else can help you borrow more, without owning any share of the property.

In this guide, we’ll break down how JBSP mortgages work, who they’re best for, and when they can be a smart solution.

What Is a Joint Borrower, Sole Proprietor Mortgage?

A JBSP mortgage allows an extra person (usually a parent or close family member) to go on the mortgage but not on the property deeds.

This means:

They share responsibility for paying the mortgage.
They don’t own any part of the home.
They’re not caught by the extra 3% stamp duty surcharge that applies to second-home ownership.

It’s basically a way to boost affordability without adding someone as a legal owner.

Why Would Someone Use a JBSP Mortgage?

To Increase Borrowing Capacity

If your income doesn’t stretch far enough on its own, a second applicant’s income can help you borrow more. This is especially common for:

First-time buyers facing high house prices
Single applicants
People with lower or inconsistent income

To Get on the Ladder Earlier

Instead of waiting to increase income, build savings or pay off debts, a JBSP mortgage can speed up the process.

To Avoid Family Members Owning Part of the Home

Parents often want to help, but don’t want to be tied to the property legally. JBSP works perfectly here.

To Avoid Stamp Duty Surcharge

If a parent went on the deeds, they may pay the additional 3% stamp duty. JBSP avoids this because the helper isn’t a legal owner.

Who Are JBSP Mortgages Ideal For?

JBSP is most commonly used by:

First-time buyers

Especially young professionals whose incomes haven’t caught up with house prices in their area.

Parents helping adult children

This is by far the biggest category. Parents can use their income to support the mortgage while the child owns the home.

Couples where one partner has lower income or credit issues

If one person can’t go on the mortgage (credit, affordability, past financial issues), they can still live in the property while the other partner and a helper apply.

Single parents

Where one income alone isn’t enough to meet lender affordability models.

Older borrowers

Sometimes adult children go on the mortgage to help parents downsize or move, though lenders vary on age limits.

How a JBSP Mortgage Works (Step-by-Step)

Borrower + helper(s) apply for the mortgage together.
Lender assesses all incomes, commitments and credit files.
Only the main buyer (the sole proprietor) goes on the property deeds.
The mortgage offer names all applicants, who share the legal responsibility for the loan.
Everyone must pass affordability, credit, age criteria and take independent legal advice.
Over time, the helper can often be removed from the mortgage when affordability improves.

Pros of a JBSP Mortgage

Boosts affordability significantly

Can help you borrow more than you could alone.

No extra stamp duty for the helper

Parents, siblings or partners help without owning part of the home

Flexible exit — they can come off later

Good for long-term affordability growth

Perfect for careers with strong income progression.

Cons to Consider

All borrowers are legally responsible for the full mortgage

If payments are missed, everyone’s credit file is affected.

Age limits can restrict mortgage terms

If the helper is older, their age may reduce the maximum mortgage term.

The helper’s borrowing may be affected

Their income is tied to this mortgage, which can limit their future applications.

Some lenders require legal advice

Independent legal advice is often mandatory for the non-owner borrower.

When Does a JBSP Mortgage Work Best?

When the main buyer’s income is rising

For example, early-career roles with strong salary progression.

When the helper has stable, strong income

Often a parent or relative with good credit and minimal debts.

When other options don’t fit

Such as when:

A guarantor mortgage isn’t available
A gifted deposit still isn’t enough
A partner can’t go on the mortgage

When avoiding stamp duty surcharge matters

A JBSP mortgage can work really well when one partner already owns a property and the couple want to buy a home together, but don’t want the existing property to trigger the additional 3% stamp duty surcharge.
Instead of adding the partner who already owns a property to the deeds, they can simply go on the mortgage to support affordability — avoiding the second-home tax charge.

**When JBSP Might Not Be Suitable**

If the helper wants to own part of the home → Joint mortgage may be better.
If the helper is near retirement → affordability may be restricted.
If the buyer’s income won’t realistically improve → removal later may be hard.
If multiple applicants already have commitments → affordability may still fall short.

Can the Helper Be Removed Later?

Yes — this is one of the best parts of JBSP mortgages.

Once the main borrower’s income improves, or once debts are reduced, you can request a remortgage or product transfer to remove the helper.

Is a JBSP Mortgage Right for You?

Every situation is different. A JBSP mortgage can be incredibly helpful for buyers who need extra support to get onto the property ladder, but it isn’t right for everyone.

Speaking with a broker gives you personalised guidance, checks lender criteria, and helps you choose the right solution for your circumstances.

Need Advice?

If you’d like to explore whether a JBSP mortgage could work for you, we’re happy to help.

Get in touch and we can run through your options, affordability and the lenders offering JBSP products right now.

If you’re just starting the journey of divorce, you might be overwhelmed with the paperwork and processes ahead of you.

Firstly, we are here to help you navigate the finances when it comes to your mortgage – so don’t panic, just pick up the phone and we’ll talk you through the process step by step as we know how worrying and overwhelming this can be.

Secondly, you might be hearing a lot about changes to Mortgage Capacity Report requirements made earlier this year. Below is a simple break-down of what you need to know.

So, what exactly is a mortgage capacity report?

A mortgage capacity report is an in-depth report detailing the amount and type of mortgage you are likely to get after a divorce or separation. Many clients use the report as a starting point for discussions regarding financial settlements including as part of DIY divorce kits. It can also be very useful for solicitors in family court proceedings and can often have a direct impact on any settlement.

What are the benefits of obtaining one?

As mentioned above, Mortgage Capacity Reports are very useful in family court proceedings and often have a direct impact on any settlement. It will also add greater creditability to your financial settlement when dealing with your solicitor.

The report will assess particular lenders’ criteria & products and will determine what you are likely to be offered. This will allow you to compare current interest rates and see the likely monthly repayments and additional costs you would be looking at post divorce/separation. This is really helpful for your own peace of mind as it will help you plan for your next chapter and help you make the decisions you’re faced with as part of the divorce.

Whereas previously, Mortgage Capacity Reports were advantageous for the reasons we’ve just outlined, in March this year, it became a legal requirement to obtain a mortgage capacity report by the time court proceedings commence.

As qualified ‘whole of market’ mortgage brokers, here at BMI we can provide you with a comprehensive mortgage capacity assessment report which will not only be accepted by solicitors and the courts but will also give you peace of mind. It is a personal and bespoke report based on your circumstances and the nature of your financial separation. This is completely dependent on your own personal circumstances and the complexity of your separation. There are many factors that can affect the outcomes of the reports and every potential scenario should be covered to ensure that you get a fair settlement from your separation.

Most importantly, your mortgage capacity report needs to be credible, realistic and accurate. This way it can:

Be used by the Court to help the Judge make a decision on finances.
Be used by the other party (ex-partner and/or their solicitors).
From the Legal Representatives perspective it can be considered “Best Practice” in the way mortgage capacity is demonstrated.
Reflect your specific circumstances.
Help you make accurate financial plans for the future.
Settle disputes between the divorcing parties.

We know that this can be a very stressful time, so our Mortgage Capacity Report will help you understand the expectations and limitations of your borrowing ability, in a clearly laid out and detailed report. Get in touch today to speak to one of our expert Mortgage Capacity Report Advisers.