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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.

The mortgage market is particularly tricky to navigate at the moment and, even though house prices around the country are falling, rates are still high and there’s a lot of chopping and changing going on, which is creating a lot of uncertainty right now.

Although rates are high, they are coming down and have been doing so regularly over the last couple of months and it’s possible that this will continue as we head into 2024… but the situation is precarious and people are sure to still be wary about property investment at the moment. 

It’s no surprise that many are having second thoughts about selling their house and moving on, with staying put an increasingly attractive option in the face of all this fluctuation.

Even if you do decide not to sell up and relocate, it’s likely that you will have to sort out a new mortgage product at some point, when your current deal comes to an end.

Most people at the moment are opting for fixed rate deals to give them a bit of certainty over how much they’ll be repaying each month – and, given that the cost of living crisis is showing no real sign of slowing down just yet, this seems like a good strategy to adopt, at least for the moment.

If you are thinking of taking out a mortgage or if you’re approaching the end of your current deal, now’s the time to start thinking about whether a two or five-year fixed rate deal would be the most appropriate for you. 

These are the most common fixed rate products, although you may find some lenders willing to offer three years or even ten years, depending on the situation.

When it comes to making your decision, you need to take into account what’s happening in the wider economy and what you think will likely happen in the future. If you think rates are likely to fall relatively soon, a two-year fixed rate product could be a good route to go down, whereas if you think they’re likely to continue going up, you might prefer a five-year deal.

The pros and cons of two-year deals

The general expectation is that interest rates are likely to hit their peak soon, which will see the base rate plateau for a bit before dropping back down, with mortgage rates following suit.

This means that between booking your new mortgage deal and completing, you could be offered significantly lower rates, it’s worth checking a few weeks before completion. Note, however, that it’s unlikely we’ll see rates fall back to the super-low levels they were at pre-pandemic, so factor this into your decision and budgeting, as well.

In terms of cons, you’ll likely find that two-year fixed products are more expensive than five-year deals. This is because the general view is that interest rates will fall from where they are now over the next few years, which lenders are factoring in over the long term.