Joint Borrower Sole Proprietor

Helping more people to find a place to call home

Joint Borrower Sole Proprietor helps clients who can't borrow enough on their own, by letting them add a family member to their mortgage. It could be helpful for first time buyers with lower incomes, but any home move could use it.

How does it work?

Joint Borrower Sole Proprietor lets a client add a family member to their mortgage to improve their affordability.

They'll be jointly liable for the mortgage, but only the client will own the property and be named on the title deeds. The client is known as the 'owner-borrower' and the family member 'non-owner borrower'. 

E.g. George wants to buy his first home

George earns £30,000 and needs a £150,000 mortgage
The maximum loan he's offered is £110,000, which is £40,000 short
George's mum earns £60,000. She's added to the mortgage, and they get £150,000
With a Joint Borrower Sole Proprietor mortgage George is able to buy his first home
They are both liable for mortgage payments and named on the Mortgage Deed
Only George owns the property and is named on the Title Deeds.

Lending criteria

  • Maximum 2 borrowers
  • Purchase only
  • Non-owner borrower must be an immediate family member
  • Minimum income £20k for owner borrower
  • Excludes Interest Only, Concessionary Purchase, Cascade Score, Boost LTI and Deposit Unlock
  • Independent legal advice required for the non-owner borrower
  • Non-owner borrower’s household expenditure and debts will be captured.
  • For both applicants (including the non-owner borrower), the maximum age at the end of the term is 80. For more information see terms into retirement.


With a Joint Borrower Sole Proprietor mortgage, the other person agrees to contribute equally to the mortgage repayments. With a guarantor mortgage, the other person only becomes responsible for the repayments if you can't make them. In both cases, the other person has no legal claim to the property.
Only Immediate family members can be added to the mortgage. This could be a mother, father, grandparent, sibling, child, or grandchild.
The non-owner borrower must get independent legal advice before completion. Confirmation of this will be needed.
Complete an application as normal but select the Joint Borrower Sole Proprietor option under 'Property Ownership Type' on MSO. For a borrowing figure, select Joint Borrower Sole Proprietor on our affordability calculator.
Select ‘New Build’ at the Decision in Principle stage, MSO will then generate the right outcome.