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.

For many people who have paid off a significant amount of their mortgage or are debt-free entirely, their home is often the most valuable asset they have.

This is increasingly the case given the average house price in the UK has nearly doubled since records began in 2005, meaning that people who bought a house and have paid off a significant chunk of the mortgage have a lot of potential to take advantage of that surplus value.

There are many ways to do this, from selling and downsizing in order to acquire additional money or by taking advantage of a range of equity release schemes on the advice of financial experts.

Releasing the equity in a home has a lot of risks and is not the right solution for everyone, but can be an ideal way to acquire money for retirement or to give to loved ones to help them get onto the property ladder in lieu of waiting for an inheritance.

How Does Equity Release Work?

To understand what an equity release scheme is, it is also important to understand the concept of equity with regard to property.

At a basic, general level, equity is the value of an asset after any debts or liabilities have been subtracted from it, which in the case of a house means how much it can be sold for minus any mortgage or loans secured against it.

A basic example of this is that if someone took out a mortgage to buy a home for £200,000 and paid off £100,000 of that mortgage whilst the home increased in value to £250,000, that would mean that once that remaining £100,000 of debt is subtracted that there is £150,000 of equity available.

The simplest way to release that equity is to sell the home, which would give you £150,000 once the mortgage has been paid off, discounting fees and interest. But this means moving house, and during a strong housing market that can offset the benefits a homeowner will get from selling.

An alternative, therefore, is releasing the equity, which is a form of financial product that allows a homeowner to tap into that equity.

This typically takes the form of a lifetime mortgage, where money is borrowed against the home whilst the homeowner continues to own it and live in it.

Once they die or move into long-term care, the house is then sold and any proceeds are used to pay the loan back. If there is any money left over, that money will go to the beneficiaries of your estate.

An alternate option is a home reversion scheme, where a homeowner sells their home to a specific provider with the provision that they have the right to live in it until they die or move into long-term care.

Typically, one should never sign up for an equity release scheme without a no-negative equity guarantee.

This means that if the value of the house falls and it cannot be sold for enough to pay off the mortgage, then the difference does not need to be paid back, something that was previously a huge problem before the Equity Release Council due to the interest roll-up.

When Is Equity Release Right For You?

An equity release is a huge decision, and as with any other major financial decision, it should not be taken without careful consideration and the advice of experts.

Whilst not as risky an option as it used to be thanks to no-negative-equity guarantees being far more common, it is important to reach the terms of your agreement very carefully, as letting the property fall into disrepair or letting out rooms could potentially be a breach of conditions.

As well as this, an inherent consequence of equity release is that you can no longer leave your home to your loved ones, so make sure that they are involved in the process. This will stop them from being surprised by the final part of the process during an already difficult time.

It is also important to understand that releasing equity can affect your pension, universal credit and other benefit entitlements, so before you sign up for a scheme, make sure to ask a specialist advisor about the impact on your entitlements and whether it is still the right choice for you.

However, if your savings, pension and other revenue sources will not be enough to sustain your need, downsizing is not an option and either you have no beneficiaries or you are okay with them having a reduced inheritance, equity release can help you use money tied up in your home now.