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:
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.
