JBSP mortgage (joint borrower sole proprietor)
A joint borrower sole proprietor (JBSP) mortgage lets a family member, often a parent, add their income to boost how much you can borrow, while only you own the home and appear on the title deeds. Because the supporter takes no ownership stake, it can avoid a second-property stamp duty surcharge for a parent who already owns. The supporter is, however, fully liable for the mortgage.
How it works
On a JBSP mortgage, two or more people are named as borrowers and are jointly responsible for the payments, but only you are the legal owner. The lender adds the supporter's income to the affordability calculation, which can lift your maximum loan well above what your income alone would allow. Crucially, the supporter is not on the deeds, so they own no part of the property.
Why people choose JBSP over a joint mortgage
- The home is entirely yours: the supporter owns no share.
- A parent who already owns a home avoids adding a second property to their name, which can sidestep the higher-rate stamp duty surcharge.
- It can be structured so the supporter steps off the mortgage later, once your income has grown.
The honest risk
The supporter is fully responsible for the mortgage despite owning nothing. If payments are missed, it affects their credit and they can be pursued for the debt. Lenders often require them to take independent legal advice so they understand this. It is a generous arrangement, but it should be entered into with eyes open on both sides.
Common questions
What is a JBSP mortgage?
Joint borrower sole proprietor means several people are jointly responsible for the mortgage, but only one (you) owns the property and is on the title deeds. A parent's income is added to boost how much can be borrowed, while they take no ownership stake.
How is it different from a joint mortgage?
On a normal joint mortgage everyone borrows and everyone owns. On JBSP the supporting person borrows but does not own. That keeps them off the deeds, which can avoid a second-property stamp duty surcharge for a parent who already owns a home, and keeps the property fully yours.
Who does JBSP suit?
First-time buyers whose own income is not quite enough, but who have family willing to back the borrowing. It is common for a parent to support an adult child. The supporting person must be comfortable being liable for the mortgage if you cannot pay.
What are the risks for the supporting person?
They are fully liable for the mortgage even though they do not own the home, so a missed payment affects their credit and they could be pursued for the debt. They should understand this clearly, and many lenders ask them to take independent legal advice.
Compare with a guarantor mortgage, or read it in plain words: I want to help my child buy their first home.
Founder, MortgageExplained, MortgageExplained
Adam spent nearly a decade as a mortgage adviser at Just Mortgages, with further experience in commercial finance. He is CeMAP and CF qualified. He built MortgageExplained to do one thing well: explain mortgages in plain English, then introduce you to a regulated broker when you are ready. Every page is written and reviewed by Adam.
Last reviewed: 29 June 2026