Porting a mortgage when moving home: what to check
Porting a mortgage means applying to take your existing mortgage deal to a new property. It is not an automatic transfer: the lender reassesses affordability, the new property and any additional borrowing.
Ask your lender for a porting illustration before committing to a move. MoneyHelper notes that porting is treated like a new mortgage application. If you need extra borrowing, the additional amount may sit on a separate rate/product from the ported balance.
The rate may be portable; the mortgage approval is not
A mortgage offer can say the product is portable, but moving home changes the security. The lender still needs to accept the new property and your current financial position.
If your income has fallen or you have taken on new debt, you may not pass today’s affordability assessment even though you have paid the existing mortgage perfectly for years.
Start with a dated baseline. List every existing mortgage part, balance, rate, product end date and early-repayment charge, then add the price and deposit for the new property. Portability of a rate does not remove the need for a new affordability and property assessment.
For porting a mortgage when moving home: what to check, cross-check the expected result against the actual result in the section 'The rate may be portable; the mortgage approval is not'.
Use “The rate may be portable; the mortgage approval is not” as a decision checkpoint on Porting a mortgage when moving home: what to check. Save the current screen, statement or tariff that supports your conclusion, and note what result would make you stop, contact the bank or choose a different route. That keeps the next step evidence-led.
Additional borrowing can create two mortgage parts
Suppose you owe £180,000 on a 2.2% fixed deal and need £250,000 for the new home. The lender may port £180,000 on the old rate and lend the extra £70,000 on a current product. That leaves two parts with different rates and potentially different end dates.
Ask how the lender will align those parts later. A cheap port today can create awkward remortgaging choices if one fix ends in 2027 and the other in 2029.
Worked example: you may port £180,000 of an existing deal but need another £40,000 for the new home. The extra borrowing can sit on a different rate or product, so compare the combined monthly payment and fees rather than looking only at the attractive old rate. That is more useful than asking whether the product or process is good in general.
For porting a mortgage when moving home: what to check, cross-check the expected result against the actual result in the section 'Additional borrowing can create two mortgage parts'.
Check early-repayment charges if the sale and purchase do not line up
Some lenders waive or refund an early-repayment charge when the old mortgage is redeemed and the new one completes within a specified window. The details are lender-specific.
If there is a gap between selling and buying, ask for the exact refund period in writing. Missing it by a few days can turn a seemingly portable mortgage into a costly exit.
Use a fixed sequence rather than repeated trial and error. ask the lender or broker to show the ported part, any top-up part, fees, valuation assumptions and what happens if the sale and purchase dates do not match. Keep the illustration so the final offer can be checked line by line. After each step, record what changed and what did not.
For porting a mortgage when moving home: what to check, cross-check the expected result against the actual result in the section 'Check early-repayment charges if the sale and purchase do not line up'.
The new property can break the port
Lease length, construction type, valuation, location or property use can make the new home unacceptable security. Portability does not override the lender’s property criteria.
Have the broker/lender look at unusual property features early. There is little value negotiating the perfect port if the lender will not lend on the flat you are buying.
Timing can change the outcome. the sale redemption and new completion need to be coordinated. A gap between them can change whether an early-repayment charge is taken and later refunded, so confirm the lender process before exchange rather than assuming the transactions will automatically line up.
For porting a mortgage when moving home: what to check, cross-check the expected result against the actual result in the section 'The new property can break the port'.
Use “The new property can break the port” as a decision checkpoint on Porting a mortgage when moving home: what to check. Save the current screen, statement or tariff that supports your conclusion, and note what result would make you stop, contact the bank or choose a different route. That keeps the next step evidence-led.
Compare porting with a clean remortgage
Calculate the value of keeping the old rate against any early-repayment charge, fees and the new lender’s rate. A very low old fixed rate can be worth preserving; an old rate close to market may not justify complexity.
Ask for pound figures over the period you expect to keep the mortgage. “Avoiding an ERC” is not automatically a saving if the alternative mortgage is cheaper overall.
If the normal route fails, switch from retrying to evidence. if the new property, loan-to-value or affordability result changes the port, ask for the revised cost in pounds and the reason. Compare that outcome with a fresh remortgage instead of continuing only because you started with the intention to port.
For Porting a mortgage when moving home: what to check, turn “Compare porting with a clean remortgage” into one verifiable fact rather than a general impression. Record the amount, status, date or rule that matters, then compare it with the bank’s current information before you make the next transaction or account decision for “Compare porting with a clean remortgage” on Porting a mortgage when moving home: what to check.
Synchronise the old redemption and new completion
Porting often works most smoothly when sale and purchase complete together. If they do not, the old mortgage may be redeemed first and any ERC refund can depend on completing the new mortgage within the lender’s stated period.
Ask the conveyancer and lender how funds flow on the day and what happens if the chain breaks. The rate may be portable on paper, but poor timing can still create a temporary ERC or force short-term financing.
Worked example: You owe £180,000 on a mortgage with a rate you would like to keep, but the new home requires borrowing £240,000. Porting does not normally mean the old loan is simply moved unchanged to the new address. The lender will assess the new property and your current affordability, and the additional £60,000 may sit on a different product and rate.
Timing matters because the sale, redemption of the old mortgage and completion of the new purchase can interact with early-repayment charges and porting conditions. Ask the lender or broker what happens if the sale and purchase complete on different dates, and whether any charge can be refunded if the new borrowing completes within the lender’s permitted window.
Compare the whole new arrangement, not only the attractive rate on the ported portion. Product fees, the rate on extra borrowing, term changes and monthly payment can outweigh the benefit of preserving one part of the old deal.
Use one closing decision rule. choose the option with the better total cost over the period you realistically expect to keep the mortgage, after fees and charges. Porting is a feature to compare, not a guarantee that staying with the existing lender is cheapest.
Sources and verification
Hannah Lewis - Mortgages & Loans Specialist
Porting is a fresh mortgage application wearing an old product rate. Model the ported balance, any top-up borrowing and ERC timing together before assuming your current deal will follow you to the next home.
MyBankAnswers uses official provider and UK regulatory sources wherever practical. Information is general and does not constitute financial advice.