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

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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)

  1. Borrower + helper(s) apply for the mortgage together.

  2. Lender assesses all incomes, commitments and credit files.

  3. Only the main buyer (the sole proprietor) goes on the property deeds.

  4. The mortgage offer names all applicants, who share the legal responsibility for the loan.

  5. Everyone must pass affordability, credit, age criteria and take independent legal advice.

  6. 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.

When navigating an increasingly complex property market, it always pays to have a guide, and one of the best tools for closing sales and getting favourable mortgage rates and terms depending on your circumstances is a mortgage broker.

A mortgage broker is an ideal intermediary between buyers and mortgage lenders, as they quickly learn what a buyer needs and their circumstances and can use their network of lenders and their expertise to track down the best possible deal.

In the current market with so many questions up in the air, having a broker on hand to cut through the confusion and provide advice on how to manage often rapidly changing conditions and products on offer is exceptionally helpful.

They can save time trying to learn everything about the market and go through the paperwork with buyers, helping ensure their application is right the first time, as well as giving the buyer a chance to sample a wide range of lenders at once.

This makes them very useful and worth it in a wide range of circumstances, but there are some situations where a broker is not only important, but they are a vital necessity.

The distinct difference between going to a broker and going directly to a lender is that they work for the client, whereas the bank or building society employee works for a specific company. 

Brokers serve their clients and have their interests in mind, while banks won’t let clients know if rates have been reduced and that they could pay less to borrow the same amount. Brokers, meanwhile, will continue to check the markets over time to find the best rates going.

Another clear benefit of using a broker is that the wait time is significantly lower. If you go through the banks, you’ll get in touch with them for an appointment and you’ll likely have to wait weeks. 

But with brokers, a meeting can be arranged to take place within 24 to 48 hours. This meeting will also be tailored to suit your needs and what’s important to you, whereas meetings with bank employees are largely scripted.

You’ll also have access to a broad range of lenders if you use a broker. For example, lenders like Precise, BM Solutions & Accord can only be accessed by using a mortgage broker.

What Are Broker-Only Mortgages?

Many lenders are available through the high street, and so whilst it can often be easier to go through a broker, theoretically it is possible to walk into a branch or visit a website and access some mortgage products directly.

However, whilst using a broker is advisable here, it is technically not required. However, there is a particular class of mortgage that cannot be accessed except through a broker.

Intermediary-only mortgages, or broker-only mortgages, are products typically provided by the many specialist lenders that also only work through a set of approved brokers and will not provide mortgages directly to members of the public.

These deals are often exclusive to the broker and can often end up being on particularly favourable terms, especially when it comes to greater flexibility and more bespoke, tailored arrangements due to working with a trusted broker, along with a better chance of approval.

As well as specialist broker-only lenders, many mainstream lenders have broker-exclusive deals as well, meaning that even buyers planning on working with a conventional big-name lender would potentially benefit by going through a broker.

Why Should You Get A Broker-Only Mortgage?

Working with a broker is advisable, but there are a lot of benefits that come through working in the brokerage system, many of which are not available in retail products.

The most common reason to go through a broker is not only the wider range but a wider understanding of the potential options and how they differ and improve on the ones available at retail.

This advice is the main selling point and could help close the deal on the perfect mortgage that through savings and favourable terms more than pays for the fees.

Another major feature, one that makes it increasingly valuable to younger first-time buyers today is the option for more flexibility, including longer-term mortgages than the norm, enabling people who do not necessarily have huge incomes to get their foot in the door and reap the benefits of home ownership.

Conversely, many retail mortgages have strict overpayment limits, given that the main profit they receive is through the interest on repayments. Some broker-only mortgages can remove this cap, allowing buyers to pay more when they can and cut their loan term short.

However, by far the biggest use case for broker-only mortgages comes from more complex mortgage requirements and buyers who deviate from the normal ideal retail lenders want.

People who are self-employed, those who work in certain specialist professions or people buying properties with complex conveyancing issues such as thatched roofs and listed buildings can often struggle to get conventional mortgage products.

Working with a broker puts them in touch with specialists who can supply them with the finance they need to make their unconventional dream a reality, primarily through using alternative criteria to ensure suitability.

Finally, and most importantly, people who suffer from a bad credit history or even an outright discharged bankruptcy have a higher chance of getting approval, as a mortgage broker can work directly with them and more effectively ascertain their chances of repayment, taking into account LTVs.

This can be particularly important for those who passed eligibility criteria initially, only to be declined after further eligibility checks raise concerns.  

A broker can help provide expert advice and work directly with lenders to make the best case for unconventional borrowers to find the lenders that suit them best.