You have found a buyer, spotted the next home and your current mortgage deal still has two years left to run. Then someone says, “Just port it.” Sounds simple. It often is not. How mortgage porting actually works is one of the most misunderstood parts of moving home, and getting it wrong can leave you with an unexpected early repayment charge, a higher rate on extra borrowing, or a declined application at the worst possible moment.
Porting can be valuable, particularly when your existing fixed rate is lower than what is available today. But it is not a lender handing you a golden ticket. You are still asking for a new mortgage on a new property. The lender remains firmly in control.
How mortgage porting actually works
Mortgage porting means taking your existing mortgage product – usually its interest rate and remaining deal period – from your current home to the property you are buying. Strictly speaking, you are not physically moving the old loan from one title deed to another. Your current mortgage is repaid when your sale completes, and the lender creates a new mortgage on the new property using the portable terms of your old deal.
That distinction matters. A portable mortgage product does not mean guaranteed borrowing. The lender will normally assess your application again before agreeing to the move.
They will look at your income, employment, outgoings, credit history, deposit or equity, the property you are buying and whether it meets their lending rules. If you have changed jobs, become self-employed, taken on car finance, had a baby, reduced your hours or missed payments since your first mortgage was approved, the answer may be different this time.
This is the bit many borrowers are never told clearly: porting is a fresh mortgage application. The rate may be old. The underwriting is very much current.
Why people choose to port
The main attraction is avoiding an early repayment charge, often called an ERC. If you are tied into a fixed, tracker or discounted deal and repay it early, your lender may charge a percentage of the balance. On a sizeable mortgage, that can run into thousands of pounds.
If your product is portable and the lender approves the new loan, porting may allow you to keep the existing rate and avoid that charge. For someone sitting on a competitive rate, that can make a real difference to the cost of moving.
But do not stop the calculation there. A deal that looks brilliant because it avoids an ERC can still be the wrong choice if you need a large amount of extra borrowing at an expensive rate, or if the lender’s criteria make the transaction difficult. The right comparison is the overall cost, not the one number the lender wants you to focus on.
Moving to a more expensive home
Most movers need to borrow more. This is where mortgage porting becomes a two-part arrangement.
Your existing balance may be ported at the rate and terms of your current product. The additional borrowing is usually placed on a separate product at the lender’s current rate. You could therefore have two mortgage parts, with different interest rates and different fixed-rate end dates.
For example, imagine you have £180,000 left on a 2% fixed rate with two years remaining, but need £80,000 more to buy your next home. Your lender may let you port the £180,000 at 2%, while the extra £80,000 is offered at a current rate that could be much higher. The combined payment might still be sensible, but it needs proper modelling.
There is another trap. When the original fixed rate ends, you may have one mortgage part coming up for review before the other. That can make a future remortgage less straightforward. A good adviser will plan for the exit, not just celebrate getting the keys.
The loan-to-value problem
The rate available on the additional borrowing often depends on loan-to-value, or LTV. That is the size of your mortgage compared with the value of the new property. A bigger deposit or more equity can put you in a better pricing band. A smaller deposit can mean the extra borrowing is far more expensive than expected.
The lender’s valuation is what counts, not simply the estate agent’s asking price. If the surveyor values the property below the agreed purchase price, your LTV rises. You may need to find more cash, accept a pricier rate or renegotiate the purchase.
Moving to a cheaper home
Porting to a cheaper property can be just as awkward. If you need a smaller mortgage than your current balance, your lender may allow only part of the mortgage to be ported. The amount you cannot port is repaid, and an ERC may apply to that portion.
Some products include an annual overpayment allowance – commonly 10%, though it varies – which can reduce the charge. Others have specific downsizing provisions. Never assume either applies. Read the mortgage offer and ask for the figures in writing before committing to a sale.
If you are downsizing dramatically, paying the ERC and switching to a better overall deal can sometimes be cheaper than forcing a port. It depends on the balance, penalty, new rates, fees and how long you expect to keep the new mortgage.
The property still has to pass the lender’s rules
Your finances can look perfect and the port can still fail because of the property. Lenders have different views on flats above commercial premises, ex-local authority homes, high-rise blocks, unusual construction, short leases, flood risk and properties with restrictive covenants.
Do not make the mistake of assuming your current lender will accept the next property because they accepted your current one. Criteria change. Valuers also make case-by-case judgements.
This is why getting an agreement in principle and discussing the property type early matters. It is much better to uncover a problem before you spend heavily on surveys, legal work and searches.
Timing can make or break the port
A port usually works best when your sale and purchase complete on the same day. Your solicitor repays the existing mortgage from the sale proceeds and the new mortgage completes on the purchase. The lender applies the portable product to the new loan under its process.
A broken chain complicates things. If you sell first and rent temporarily, you may have to repay the old mortgage before buying again. Some lenders offer a limited “porting window”, allowing you to reclaim the ERC if you complete a new mortgage with them within a set period. Others do not, or set strict conditions.
Never rely on a verbal reassurance that you can sort it out later. Ask exactly what happens if your sale completes before your purchase, how long you have to complete the new loan, whether the ERC is refunded, and what evidence the lender requires.
When porting is not the best answer
Porting is worth considering, not blindly accepting. It may be the wrong move if your current lender will not lend enough, the additional borrowing rate is poor, the new property falls outside its criteria, or another lender offers a deal that beats the ERC once all costs are included.
Also consider flexibility. If you expect to move again soon, overpay heavily or change your mortgage term, a product with restrictive conditions can become expensive. The headline rate is only one part of the decision. Fees, incentives, repayment charges, overpayment rules and future options all matter.
A lender can only sell you its own answer. That is not impartial advice. A broker can compare the cost of porting against remortgaging, assess affordability before you make an offer, and identify the lenders most likely to accept both you and the property.
Questions to ask before you put your home on the market
Ask your current lender whether your exact mortgage product is portable, not whether they offer porting generally. Confirm the maximum amount you can port, the ERC if you borrow less, the rate and fees for extra borrowing, and whether your current term can be changed.
Then ask how they will reassess you. Will they use today’s affordability rules? What evidence will be needed if you are self-employed, earn commission or receive bonuses? Does the new property type create any restrictions? These answers prevent nasty surprises after you have emotionally committed to a move.
Finally, get an independent comparison. You may find porting protects a rate that would be costly to lose. Or you may find that a new mortgage gives you more borrowing power and a cleaner long-term position, even after the penalty.
Moving home is expensive enough without guessing. Before you let a lender’s simple “yes, you can port” steer the whole transaction, put the numbers under pressure. Mortgage Genius can help you compare the real options, challenge the small print and move forward with a mortgage plan that works for the home you want next.
