Learn more about guarantor mortgages in our detailed guide.

What is the difference between JBSP and a guarantor mortgage?

With JBSP, the supporting person's income is used to boost borrowing and they're on the mortgage. With a guarantor mortgage, the guarantor provides security (often their property) but their income isn't usually used for affordability calculations.

Do parents pay stamp duty on a JBSP mortgage?

No, parents don't pay the additional stamp duty surcharge on a JBSP mortgage because they're not on the property deeds. Only the person named as proprietor (owner) is liable for stamp duty at the standard rate.

What happens if I miss payments on a JBSP mortgage?

All borrowers are jointly liable for the mortgage. If payments are missed, the lender can pursue any or all borrowers for the debt, including the supporting parent whose income was used but who doesn't own the property.

Can grandparents be on a JBSP mortgage?

Yes, grandparents can be supporting borrowers on a JBSP mortgage. However, lenders have maximum age limits (typically 70-80 at end of term), so the mortgage term may need to be shorter to accommodate this.

Quick Answer

What Is a Joint Borrower Sole Proprietor (JBSP) Mortgage?

Last reviewed: December 2025

Reviewed by Jay Sabine – CeMAP Qualified – 29 years experience

A JBSP mortgage allows a family member to boost your borrowing power without being on the property title.

A Joint Borrower Sole Proprietor mortgage is designed to help first-time buyers who can't borrow enough on their own. With JBSP, a parent or family member joins the mortgage as a borrower (their income is included in affordability calculations) but they're not on the property deeds. This means they don't own any part of the property, avoiding the stamp duty surcharge on second homes and potential capital gains tax. It's particularly useful for helping children onto the property ladder.

Your home may be repossessed if you do not keep up repayments on your mortgage. Your Home Finance Ltd is authorised and regulated by the Financial Conduct Authority (FCA 989177).

Key Points

1Up to 4 people can be borrowers, but only 1 or 2 own the property
2The supporting borrower's income boosts affordability
3No stamp duty surcharge as supporting borrower doesn't own property
4Supporting borrowers are still liable if payments are missed
5Popular with parents helping first-time buyer children
6Some lenders have age limits for supporting borrowers (typically 70-80)

Eligibility Criteria

The property owner(s) must typically be first-time buyers
Supporting borrowers need good credit and stable income
Combined income must pass affordability assessment
Maximum age at end of mortgage term applies to all borrowers
Supporting borrowers cannot already own a share of the property

Typical Timeframe

JBSP mortgages have the same timeline as standard mortgages - typically 2-4 weeks from application to offer. Additional documentation may be needed from the supporting borrower.

Next Steps

1Discuss with family members who might be willing to support
2Gather income documents for all borrowers
3Calculate combined affordability with a specialist broker
4Understand the liability responsibilities for supporting borrowers
5Compare JBSP against guarantor mortgages to find the best fit

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What Is a Joint Borrower Sole Proprietor (JBSP) Mortgage?

Key Points

Eligibility Criteria

Typical Timeframe

Next Steps

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