Moving house does not always mean leaving your mortgage deal behind. If you secured a competitive fixed or tracker rate, porting a mortgage in the UK may let you keep that deal when you buy your next home. But the process is not automatic, particularly if your income has changed or you need to borrow more.
The question is not simply whether your mortgage is portable. It is whether your lender will approve the move, how much borrowing can retain the old rate, and whether porting costs less than a new deal.
What does porting a mortgage actually mean?
Porting means taking the interest rate and relevant features of an existing mortgage product to a new property, subject to approval. The old mortgage is repaid when you sell, and a new loan is secured against your next home. It is the product that moves, not the original debt or legal charge.
Many UK mortgages are portable, but check your offer documents. Even a portable mortgage UK borrowers already hold does not guarantee approval for another property. The lender considers your new application under its current requirements.
Why your lender reassesses affordability
When you first borrowed, the lender assessed your finances at that time. Moving home triggers a new lending decision, even if you want to keep the same balance and rate.
The lender may review payslips or accounts, debts, credit history, dependants and the proposed term. Reduced income, a move into self-employment or higher expenses could affect approval. The lender also values the new property and checks its security criteria.
Loan-to-value, or LTV, matters too. It compares your borrowing with the property’s value. A disappointing valuation can increase your LTV and affect the offer. Understanding loan-to-value ratios before making an offer can help avoid surprises.
How the mortgage porting process works
Start with your existing lender
Ask whether your deal is portable, when the rate ends, what balance is eligible, and what happens if your sale and purchase complete on different dates. Request details of any early repayment charge, or ERC.
Check what you can borrow
Discuss affordability and, where available, obtain a decision in principle before committing to a purchase. This is an initial indication, not a binding mortgage offer. If you need additional funds, check the rates and fees.
Apply against the new property
The lender assesses the application, arranges a valuation and issues an offer if you qualify. Your solicitor or conveyancer coordinates repayment of the old mortgage and completion of the new one. Keep your adviser informed if moving dates change.
What happens if you need to borrow more?
Upsizing is where porting becomes especially interesting. Your existing deal’s rate generally covers only the eligible amount you port. Extra borrowing normally comes on a separate product at a current rate. The two parts may have different fixed-rate end dates, fees and repayment conditions.
Imagine you owe £140,000 and sell your current home for £300,000. Ignoring selling costs, that releases £160,000 of equity. You buy for £375,000 and use that equity as your deposit. You need a £215,000 mortgage: potentially £140,000 on the ported deal and £75,000 on a new rate, subject to approval and purchase costs.
Comparing only the original interest rate can be misleading. Ask for combined monthly repayments, total fees and the dates when each part needs reviewing. A guide to mortgage affordability can also help estimate a realistic budget.
What if you are borrowing less?
Downsizing creates a different problem. If you need a smaller mortgage than your outstanding balance, you may port only part of the deal. The amount no longer needed is repaid, and an ERC may apply while an early repayment charging period remains.
For example, porting £100,000 from an outstanding £140,000 loan could mean repaying £40,000. Check your lender’s partial-porting rules and the exact charge before assuming downsizing is penalty-free.
Could you face an early repayment charge?
A successful port under the lender’s conditions can avoid an ERC on the amount transferred. Charges may nevertheless arise if you leave the deal, borrow less, or have a gap between selling and buying. Some lenders allow a limited period to complete and may refund an ERC paid at sale after eligible porting. Deadlines and refund rules vary, so get them in writing.
If a chain collapses or your lender declines the property, porting may no longer be possible. Review early repayment charges alongside legal fees, valuations, product fees, removals and any applicable property tax. A low rate alone does not reveal the total moving cost.
When might a new mortgage be better?
Keeping an older low rate can be attractive, especially when leaving would trigger a substantial charge. Yet porting is not necessarily the cheapest route. Another lender may offer a competitive whole-loan deal, or your existing product may be nearing its end.
Compare porting with new offers over the same period. Include ERCs, product fees, repayments and the effect of different mortgage terms. A qualified mortgage broker can explain restrictions that are easy to miss when you move house with a mortgage.
Questions to ask before making an offer
Get confirmation of eligibility, maximum borrowing, valuation requirements and how much retains your current rate. Ask what happens if completion dates change, how long the offer lasts, and when any ERC is payable. These answers can materially change your moving budget.
Frequently asked questions
Can I port my mortgage to a more expensive house?
Potentially, yes. You must pass affordability and property checks. If you need more than your existing balance, the extra borrowing is generally on a separate deal rather than your old rate.
Can my lender refuse to port a portable mortgage?
Yes. Portability is a product feature, not an unconditional right. A lender may decline because of affordability, lending criteria, the proposed property or other underwriting concerns.
Do I need a solicitor when porting?
Yes. Buying and selling mortgaged property involves conveyancing. Your solicitor or conveyancer handles the legal work, including redemption of the existing loan and the new lender’s security.
Will I keep my fixed rate for another full term?
Usually not. You typically retain the deal for its remaining promotional period rather than restarting the fixed-rate clock. Extra borrowing may have a different end date.
Making the decision
Porting is best treated as a fresh purchase application with a valuable option attached: preserving your existing deal. Confirm eligibility early, calculate your total borrowing requirement and compare overall costs before committing. That way, the mortgage supports your move rather than becoming an unexpected obstacle.