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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 first part of a new calendar year and the last part of a financial year is often a time when people take stock of what they currently have and start to consider what tomorrow will bring for them.

However, for some people, that fresh start can come from exceptionally unfortunate circumstances, ones with far-reaching ramifications beyond the clear personal hardship that is most evident.

A legal document known as a mortgage capacity report can help make the financial complexities of separation easier, but to understand why, it is important to understand what mortgage capacity means in this context, how it is calculated and what it is for.

Explaining Mortgage Capacity

An agreement in principle is simply a guideline, useful for highlighting your ability to buy a property but would not be enough to satisfy a court.

An MCA can be required for several types of financial settlement. However, typically it is used as part of divorce proceedings for a range of different purposes.

The main role it has is in illustrating whether each party in divorce proceedings has the capacity to manage financial responsibilities related to an existing mortgage and has the capacity to secure housing, given that by definition a divorce would necessitate finding new accommodation.

Often this is used when negotiating financial settlements, as it will provide a basis for the needs and capacities of both parties and provides an independent piece of evidence if attempts to negotiate a settlement fail and it falls into the hands of a judge to arbitrate.

There are various types of MCA, but the three main ones that are requested are:

  • A standard, single-person capacity report.
  • A joint mortgage capacity report that will cover both parties of a divorce.
  • A “no-mortgage” capacity report that will illustrate that the person who requested it is unable to qualify for a mortgage.

An MCA will include details relevant to a particular divorce’s circumstances but there are several categories of information that will be covered.

One of the most obvious is the borrower’s income, which not only includes salary but also income sources from self-employment and capital gains such as those made through investments, as well as rental income for people who rent or let buildings.

Similarly, the current status of the mortgage itself and the level of equity relative to its current market value will be all factored into the report.

The borrower’s credit history, as well as common credit score criteria, will also be factored in, as will other common lending criteria. This will ascertain the amount a borrower can take on whilst factoring in the affordability stress tests required by the FCA.

As well as this, the deposit level will be included as this can affect the overall amount a borrower can expect to be able to apply for, and thus the size and scale of property they can reasonably afford. 

Finally, the borrower’s monthly outgoings, including taxes, insurance payments, utilities and other essential, immutable payments will be factored into this capacity assessment.

This can include dependents and children, as maintenance payments, childcare and familial arrangements can vary dramatically between different cases.

Once this information and other, bespoke, relevant information is included, the qualified broker drafting the report will research with different lenders to see what types of mortgages are possible.

This includes the amount borrowed, for how long, different interest rates, fees, affordability stress tests and the ultimate repayment figures a borrower could expect, as well as signalling if someone would not be able to get a mortgage.