Glossary · UK
What is Joint Borrower Sole Proprietor Mortgage?
A mortgage where a family member's income is included to boost borrowing capacity, but only the person actually living in the property is named on the title deeds, avoiding the additional stamp duty surcharge that would apply to a second homeowner.
Full Definition
A Joint Borrower Sole Proprietor (JBSP) mortgage allows a close family member -- typically a parent -- to be added to the mortgage as a joint borrower, so their income is taken into account when the lender assesses affordability, without that person being named as a joint owner on the property's title deeds. This differs from a conventional joint mortgage, where all borrowers named on the mortgage are also registered as owners, and is designed for situations such as a parent helping an adult child buy a first home by supporting the affordability assessment, without the parent wanting or needing to hold a legal share of the property. Because the supporting family member is not a legal owner of the property, a JBSP mortgage avoids triggering the additional 5% Stamp Duty Land Tax surcharge that would normally apply to a purchase where one of the buyers already owns another residential property -- a surcharge that would otherwise make it considerably more expensive for a parent who owns their own home to be added as a joint owner on a child's purchase. The parent (or other supporting borrower) remains fully liable for the mortgage debt jointly and severally with the sole proprietor, meaning the lender can pursue either party for the full amount if payments are missed, even though only the proprietor's name appears on the property's registered title. JBSP mortgages are offered by a more limited range of lenders than standard mortgages, and typically require the supporting borrower to meet their own affordability and credit checks, alongside considering their existing mortgage or rental commitments, since they remain fully liable for the new borrowing on top of any of their own. Because the arrangement can affect the supporting borrower's own future borrowing capacity (the JBSP mortgage debt usually counts against them for affordability purposes on any future lending) and does not give them a legal share of the property, families considering this route are often advised to take independent legal advice and consider a formal declaration of trust or family agreement recording the parties' intentions, particularly around what happens if the relationship or living arrangements change.