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.

We know how stressful it can be trying to get a mortgage, and at times it can seem like climbing Mount Everest! The pandemic also hasn’t made the process any easier for many people, especially those that have lost jobs or were hit financially. BUT, there are ways you can improve your odds and make the process easier and more simple, such as staying on top of your credit report.

You’ll need to be as attractive as possible to all lenders if you want to get the most suitable mortgage deal. We strongly recommend you get to know and understand your credit report before starting the mortgage application process.
You need to convince mortgage lenders that you’ve got the financial discipline required to pay back your mortgage. One way they will investigate this is by analysing and assessing your credit report to find out if you have a good repayment history.

Your credit report lists details from any accounts you’ve had open over the past six years, including:
• Credit cards
• Loans
• Overdrafts
• Mortgages
• Some utilities

As mortgage brokers, we highly recommend using ‘Check My File’ (Multi-Agency Credit Report | Free for a 30 Day trial – Cancel at Any time, then £14.99 per month thereafter | CheckMyFile), the UK’s most detailed online credit report. With Check My File, you can see your data from 3 Credit Reference Agencies, as opposed to just 1, get an independent view with your CheckMyFile Credit Score and once the mortgage application process is over, it’s really easy to cancel.

If you check your report and it isn’t quite what you expect, please don’t worry, you can change this. One of the most important factors is to make all credit payments on time. This ensures you don’t get any extra charges and lets you avoid having any missed or late payments on your credit report.

Three more things to remember are:
• Avoid applying for credit in the six months before your mortgage application. Each time you apply for credit, a hard search is recorded on your report – too many of these can make it look like you’re overly reliant on credit
• Register to vote, as being on the electoral register helps companies confirm who you are and where you live
• Stay within your credit limits – if possible, keep balances at 25% or less of your limit, as this may help your score.

And don’t forget to check your report is accurate and up-to-date, even a small change in the way your address is noted can affect your credit score.
If you find anything on your credit report that needs correcting – e.g. an address or a payment – get in touch with the lender in question immediately and ask for them to amend it.

That said, it isn’t just about your credit score when obtaining a mortgage. Lenders will want to see if you can afford your mortgage before they lend you the money, and be less of a risk to them. So, as well as looking at your credit history they will look at how much you earn, and how much goes out. Not only credit repayments but regular, fixed costs such as childcare, council tax and other outgoings you have on a monthly basis.
If you can show them that you can afford your monthly mortgage payments even if your life situation changed or if interest rates (and your monthly payments) went up, it may help you get a mortgage even if your credit score isn’t the best.

Click the link below to check your credit report for free (free for a 30 day trial, then £14.99 per month after – cancel at ANY time):

https://www.checkmyfile.com/credit-report.htm

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