Joint Borrower Sole Proprietor mortgages

Joint Borrower Sole Proprietor (JBSP) is a residential mortgage product offered by a meaningful but limited pool of lenders. The supporter is named on the mortgage and is jointly liable for repayments. The supporter is not named on the property deeds, and the property is treated as owned solely by the borrower for both Stamp Duty Land Tax (SDLT) and capital gains tax (CGT) purposes.

Why JBSP exists

JBSP was created to let parents support adult children buying their first home without triggering the 5% additional-property surcharge. If parents go on the deeds of a residential property that is not their main home, the entire purchase attracts the surcharge. The amount at stake depends on the purchase price, the SDLT rates in force and the buyers' circumstances. JBSP keeps the deeds in the buyer name only, so the surcharge should not normally apply, subject to individual circumstances and the SDLT rules in force. Confirm the position with your conveyancer or tax adviser.

Lender criteria for JBSP

Lender appetite varies. Most majors accept JBSP for parents supporting children, but criteria differ. Common rules:

• Maximum age of supporter at end of term: usually 70, 75 or 80, depending on lender.
• Supporter must be a close family member: parent, grandparent, or sometimes sibling.
• Supporter must be able to afford the full mortgage on their own income, after accounting for any mortgage they already have.
• Loan-to-value (LTV) typically capped at 90% rather than 95%.

Worked example, JBSP versus full joint on a £300,000 purchase

Buyer income £38,000, parent income £55,000, deposit £30,000, target loan £270,000. Both routes generate the same affordability number on most lenders, around £290,000. The difference is at completion. On JBSP, the buyer alone is on the deeds, the SDLT bill is £0 (first-time buyer relief applies in full because the property is under £300,000). On full joint, the parents are on the deeds and the entire purchase attracts the 5% additional-property surcharge: £15,000 of SDLT, plus the loss of first-time buyer relief, with no offsetting benefit on the mortgage rate. JBSP is £15,000 cheaper at completion for the same lending outcome.

How JBSP differs from a guarantor mortgage

A guarantor mortgage gives the supporter no formal place on the loan paperwork; they sign a separate guarantee. JBSP makes the supporter a full joint borrower, jointly liable, and on the affordability calculation. Guarantor products are now rare; JBSP has effectively replaced them at most lenders.

The exit plan

The standard JBSP plan is to remortgage the supporter off the case once the borrower income has grown to cover the mortgage alone. Three to five years is typical. We set the plan at the start so it is in everyone mind from day one. Some lenders allow a "step-out" clause that lets you remove a borrower without a full remortgage, which avoids legal fees on the exit.

What the supporter is signing up to

JBSP is a real liability, not a paper exercise. The lender can pursue the supporter for the full balance, not just a share, if payments are missed. The mortgage shows on the supporter credit file as an active commitment, which can affect their own ability to borrow during the JBSP period. We brief supporters directly so the commitment is understood, ideally face to face with the buyer present.

Common pitfalls we see

Going full joint by default rather than asking for JBSP and losing £15,000 of avoidable SDLT. Picking a lender whose age cap on the supporter is too short for the term you need. Forgetting that the supporter own borrowing capacity is reduced for the duration. Arriving at year five with no clear path to remortgage the supporter off. We work the structure end to end and put the exit in the diary at day one.