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Boost your affordability

Add your family members' income to your mortgage application with a Joint Borrower Sole Proprietor mortgage.

What is a Joint Borrower Sole Proprietor mortgage? 


A Joint Borrower Sole Proprietor mortgage (JBSP) is when your income and the income of your family member(s) is considered when you apply for a mortgage. It is sometimes called an income booster. You can add the income of up to 4 people to your application, to possibly boost the amount you’re able to borrow. You might consider this if you’re buying a home on your own.


This type of mortgage is a temporary affordability boost to get you on the ladder. You can remove family members when you’re ready to take on the mortgage yourself. This could be if your salary increases, you inherit a lump sum, or once you've paid off a significant part of the mortgage. 


When taking out any mortgage, you should consider the long term impact. The more you borrow, the more it will cost and the more interest you will repay over time.

Benefits of an income booster

  • Add your family members

    Include the income of up to 4 people in your application.

  • Combine your incomes

    All applicants incomes are taken into consideration.

  • Increase the amount you can borrow

    You’ll be able to borrow more than if you applied alone.

  • You own your home

    The house will be legally owned by you.

Here’s how it could work

Let’s say you have a £20,000 deposit saved and you earn £30,000. You may be able to lend approximately £120,000. This means you can buy a home for £140,000 using your £20,000 plus the £120,000 you could borrow. But the home you want to buy is £200,000. With a Joint Borrower Sole Proprietor mortgage, you can ask a family member to add their name and income to your mortgage application to boost the amount you can borrow. The extra income could mean you’re able to borrow the amount you need to buy your own home.

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What are all applicants agreeing to?

Some things to be aware of:

  1. The home will legally belong to you (the homeowner)

    Only you will be named on the deed and all legal decisions. Only you can decide to sell.

  2. You’ve borrowed the loan amount together which means you are all responsible for the monthly repayments.

    You pay the mortgage repayments. But if you can’t, your family member(s) agrees to do so for you. If nobody makes the repayments, it affects the credit of everyone on the mortgage. 

  3. Additional borrowing for family members may be affected

    We take their affordability into account to boost how much you can borrow. This means they may not be able to borrow more on their own mortgage while on yours. 

  4. The homeowner is responsible for paying all fees

    Your family member won't need to pay Stamp Duty or Land Transaction Tax.

  5. Seeking independent legal advice

    It’s important that all applicants seek independent legal advice to ensure you understand what you’re agreeing to before applying.

How does it work if you’re a family member helping?

If you’re helping someone by becoming an income booster here are the things you need to know.

You can help with your family members’ mortgage affordability if you’re:   

  • Mother or father 
  • Brother or sister 
  • Child 
  • Grandparent 
  • Grandchild 
  • Legal guardian 

Your income is considered which means: 

  • Your name is on the mortgage application. 
  • You agree to make the repayments if the homeowner cannot. 
  • Your property or savings is not used as security against the loan. 
  • You may not be able to borrow more on your own mortgage if you have one, while on the income booster application. 
  • You will not own any part of the home. 

Everyone involved should take independent legal advice from a solicitor.  Your solicitor should help you all understand any risks of being named on the mortgage.  


You may also want to talk with a mortgage advisor about how your borrowing could be impacted if you’re still repaying a mortgage. 

Some things to be aware of if you’re agreeing to help a family member boost the amount they can borrow: 

  • You won’t legally own the home, the person you’re helping will.
  • You’ve borrowed together which means you’re all responsible for the monthly repayments.
  • You agree to make the mortgage repayments if the homeowner does not.
  • If the person you are helping doesn’t pay the monthly repayments, then the home may be repossessed and the credit rating for all applicants could be affected.   
  • You cannot sell the home, it belongs to the person you are helping.
  • We take your affordability into account, this may mean you cannot borrow more on your own mortgage. 
  • You are not responsible for paying Stamp Duty or Land Transaction Tax. 

Unlike a guarantor mortgage, a family member isn't offering their own property or savings as security against the loan. 


They are agreeing to make the monthly repayments if the person they are helping cannot.

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Your home may be repossessed if you do not keep up repayments on your mortgage.