Porting your mortgage: can you take your deal with you?

Porting a mortgage works by transferring your existing deal from your current property to the one you are buying. Your lender keeps the same interest rate, monthly payment, and remaining term in place, so you avoid paying early repayment charges that could run into thousands of pounds.

The process follows a similar timeline to a standard moving home mortgage application. Your lender will:

• Reassess your affordability using up-to-date income, outgoings, and credit checks, just as they would for a brand-new application
• Value the new property to confirm it meets their lending criteria, including minimum size, construction type, and location requirements
• Confirm the loan-to-value ratio on the new property falls within their acceptable range

If everything passes, your existing deal transfers across on completion day. The whole process typically takes 8 to 12 weeks from application to completion, though this depends on the length of your property chain.

You will still need a solicitor to handle the conveyancing on both the sale and purchase. Porting does not remove any of the standard legal steps involved in buying and selling property.

Whether you can port your mortgage depends on your lender, your deal, and your personal circumstances. Most fixed-rate and tracker mortgages taken out in the last decade include a portability clause, but this does not guarantee your application will be approved.

Your lender will check several things before agreeing to a port:

• Affordability: your income must still support the mortgage under current stress-testing rules, which assume rates could rise to around 8% to 9%
• Property suitability: the new home must meet your lender's criteria for property type, construction, and minimum valuation
• Loan-to-value: if your new property is cheaper than your current one, the LTV ratio could increase, which some lenders will not accept
• Credit history: any missed payments, new debts, or changes to your credit file since your original application could affect approval

If your circumstances have changed significantly since you first took out your mortgage, for example you have reduced your hours, changed jobs, or taken on additional debt, your lender may decline the port even though the clause exists in your contract.

A mortgage affordability calculator can give you a rough idea of what you might be approved for under current lending rules, but a whole-of-market advisor can run a full assessment across multiple lenders.

Porting is not always the cheapest option. The right choice depends on how your current rate compares to what is available on the open market, how long you have left on your deal, and how much you would pay in early repayment charges if you switched.

Porting tends to make sense when you are locked into a competitive rate that is lower than current best mortgage rates, and the ERCs for leaving early would be significant. If rates have dropped since you took out your deal, or your fixed period is close to ending, remortgaging to a new lender could save you more over the remaining term.

To work out which option saves you more, calculate the total cost of each over the remaining term. Include ERCs, product fees, legal costs, and the difference in monthly payments. A mortgage advisor can run this comparison for you across deals from the whole market, so you can see the numbers side by side before deciding.

Early repayment charges (ERCs) are fees your lender charges if you pay off your mortgage before the deal period ends. They are one of the main reasons homeowners choose to port rather than remortgage when moving home.

ERCs are usually calculated as a percentage of your outstanding mortgage balance, and the percentage typically decreases each year you are into your deal:

• Year 1: 5% of the balance
• Year 2: 4% of the balance
• Year 3: 3% of the balance
• Year 4: 2% of the balance
• Year 5: 1% of the balance

On a £200,000 mortgage, a 3% ERC would cost you £6,000. That is a significant sum that porting allows you to avoid entirely, provided your lender approves the transfer.

Some lenders offer a brief window, typically 30 to 90 days, between selling your old property and completing on the new one. If you cannot complete within this window, the port lapses and you may face ERCs after all. Check your lender's specific rules early in the process to avoid being caught out.

If you are approaching the end of your fixed period, the ERC may be small enough that remortgaging to a better rate still works out cheaper overall. A broker can calculate the break-even point for you.

If your new property costs more than your current mortgage balance, you will likely need additional borrowing. Most lenders allow this when you port, but the extra amount sits on a separate sub-account with its own interest rate and term.

This means you could end up with two rates running side by side: your original ported rate on the existing balance, and a new rate on the additional borrowing. The new rate will reflect current market conditions, so it could be higher or lower than your ported deal.

There are a few things to watch out for:

• Different end dates: if the additional borrowing has a different term, you will have two deals expiring at different times, which can make future remortgaging more complicated
• Higher overall LTV: the combined borrowing against the new property value increases your loan-to-value ratio, which affects the rates available to you
• Affordability limits: your lender must be satisfied you can afford both the ported balance and the new borrowing under current stress tests

In some cases, it may be simpler and cheaper to remortgage the entire amount with a new lender on one single deal, especially if the additional borrowing is substantial. If you are upsizing your home, speak with an advisor to compare the total cost of porting plus additional borrowing against a fresh remortgage.

Use a moving home calculator to estimate how much additional borrowing you might need based on your equity, deposit, and target property price.