Guarantor mortgage explained
A guarantor mortgage lets a family member back your borrowing with their income, savings or property, agreeing to cover the payments if you cannot. It can help a first-time buyer with a small deposit or limited income borrow more. It differs from JBSP, where the supporter is a co-borrower from the start. A guarantor takes real risk, so lenders usually require independent legal advice.
How a guarantee works
A guarantor promises the lender they will step in if you fall behind. That promise is usually backed by something concrete: their income supporting affordability, savings held in a linked account, or a legal charge over their own property. Because the lender has that extra security, it may lend to you where it otherwise would not, or lend more.
Guarantor or JBSP?
The two overlap but are not the same. A guarantor sits behind the mortgage and acts only on default, often with their own assets as security. A JBSP supporter is a named borrower from day one whose income is added directly, without owning the home. Some families prefer JBSP because it avoids putting the supporter's property at risk; others use a guarantor product where that suits the lender or the goal. A broker can explain which is available for your case.
Take the risk seriously
For the guarantor this is a genuine liability: their savings or home can be exposed if things go wrong. That is why independent legal advice is normally required. It can be a powerful way to help, but only when everyone understands what is at stake.
Common questions
What is a guarantor mortgage?
It is a mortgage where a family member agrees to cover the payments if you cannot, usually by backing it with their own income, savings or property as security. It can help first-time buyers with a small deposit or limited income borrow more, or borrow at all.
How is it different from JBSP?
A guarantor stands behind the mortgage and only steps in if you default, often securing the guarantee against their own home or savings. On JBSP the supporter is a named co-borrower from day one, with their income directly added to the affordability calculation. The right one depends on the lender and the situation.
What can a guarantor use as security?
Depending on the product, a guarantor may use their income to support affordability, or put up savings held in a linked account, or offer a charge over their own property. Each carries different risk for them, and not every lender offers every type.
What are the risks for a guarantor?
If you cannot pay, the guarantor must, and depending on the structure their savings or even their home could be at risk. It is a serious commitment, so lenders usually require the guarantor to take independent legal advice before proceeding.
Compare with JBSP, or see gifted deposits.
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