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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.

You wouldn’t believe it from all the negative press around mortgages and rates at the moment, but there is actually some good news this month as we see fixed rates drop across the board. Surprisingly, the housing market has remained remarkably resilient in the past six years, withstanding severe economic headwinds posed by Brexit, the coronavirus pandemic and the ongoing cost of living of crisis. Recent growth in the space has been particularly eye catching, with the average UK home value rising more than a fifth since mid-2020.

So, will the market crash or cool off?

Well, markets in other parts of the world are looking increasingly fragile. The Bank of America recently said the US market is already hitting the brakes, while Australian property values have dropped 2% since May.

But while the annual double-digit growth that the property market has enjoyed over the past couple of years in the UK looks unsustainable, a crash still appears some way off. The most likely short-term outcome is for prices to start levelling off.

A key factor for the recent spike in property valuations has been limited supply and strong demand. As a result of this, many homes have fetched well above their initial asking price. And this supply shortage remains, especially with the government continuing to fall short of its annual new homes target.

The market is likely to remain under pressure for some time, with inflation – the rate at which prices rise – set to remain high and the Bank of England likely to raise interest rates further. BUT, whilst the outlook is uncertain, a relatively soft landing for the market is still possible, given that employment rates remain high and there is a lack of properties coming up for sale.

Last week, figures from financial information service Moneyfacts showed that there are now 5 year fixed rates available below 5%, there are also other products available such as discounted or tracker products at 0.48% above base rate which is great. Again, this wasn’t widely talked about in the press and certainly a step in the right direction.

Finally, its worth noting that the Bank of England base rate doesn’t have as much impact on mortgage rates as the media may want you to believe, many lenders have already factored in a few more base rate increases, but the mortgage rates are more dependent on Swap rates or LIBOR than the base rate, these rates have been consistently dropping over the last month – 6 weeks. So it’s not all doom and gloom.

Overall, data has been pointing to a sharp slowdown in the housing market. Last week the Bank of England said the number of mortgages approved in October fell to its lowest level since June 2020. Whilst it’s welcome news that homes are selling over the asking and of course rates are finally dropping, the Bank of England’s next review of the base rate of interest is on 15 December and experts are widely predicting the Bank will increase it again, following the last rise of 0.75% to 3% last month. If that does happen, mortgage rates could increase again. So, if you’re looking for a first mortgage or are planning to remortgage in the next few months you should start looking at your options asap.