Porting Your Mortgage When Moving House: How It Works and When It Saves You Thousands

Porting is the process of transferring your existing mortgage product to a new property. You are not literally moving the mortgage — legally, your current mortgage is discharged and a new one is created on the new property, but your lender applies the same rate and terms you had before. The distinction matters because you will still go through a full application process, including a new property valuation and affordability assessment.

Most major UK lenders allow porting, including Nationwide, Halifax, Barclays, NatWest, and Santander. Nationwide's porting terms give you a 180-day window to complete your new purchase after selling your current home. Halifax offers a similar arrangement, though specific timelines and conditions vary.

The critical point: porting is not automatic. Your lender will reassess your income, outgoings, and the new property. If your financial circumstances have changed — you've switched to a lower-paying job, taken on additional debt, or the new property is significantly more expensive — you could be declined. A porting rejection does not affect your credit score in most cases, but it does leave you needing a new mortgage at today's rates.

MoneyHelper's guidance on transferring your mortgage is worth reading before you start. Their advice is independent and covers the process from the consumer's perspective, including what to do if your port is declined.

The savings from porting depend entirely on the gap between your current rate and what you'd pay on a new deal. As of March 2026, the picture is stark. UK borrowing costs have hit their highest level since the 2008 financial crisis, with gilt yields pushing mortgage pricing upward even though the Bank of England base rate has held at 3.75% since December 2025.

Consider a homeowner with a £250,000 mortgage on a 25-year term. If they locked in a 2-year fix at 2.5% in mid-2023, their monthly payment is roughly £1,120. The same mortgage at today's best 2-year fixed rate of around 4. See <a href="/posts/mortgage-guide-uk-mortgage-rates-explained-fixed-vs-variable-how-they-work-and-what-to-expect-in-2026">guide to fixed vs variable mortgage rates</a> for more details.8% would cost approximately £1,430 per month — an increase of £310 per month, or £3,720 per year.

If that fix has 12 months remaining, porting preserves £3,720 in savings over the rest of the term. Even after accounting for arrangement fees on any additional borrowing, the numbers strongly favour porting for anyone whose existing rate is more than 1 percentage point below current market rates.

The gap widens further if you're comparing against a lender's standard variable rate (SVR). Most SVRs now sit between 6% and 7.5%. A borrower who fails to port or remortgage and rolls onto their lender's SVR at 6. See <a href="/posts/mortgage-guide-remortgaging-uk-2026-when-to-switch-how-to-compare-deals-and-what-it-costs">remortgaging guide</a> for more details.5% would pay £1,689 per month on that £250,000 mortgage — £569 more than a ported rate of 2.5%. Over 12 months, that's £6,828 in unnecessary cost.

For more on timing your mortgage switch, see our guide to remortgaging six months early vs paying the SVR penalty.

Early repayment charges are the single biggest risk when porting. The FCA requires lenders to disclose ERCs clearly before you sign, and the rules are not intuitive. If you port your full mortgage balance to a property of equal or greater value, most lenders will not charge an ERC. The logic is straightforward: you're keeping the same deal, just on a different property.

But if you're downsizing or borrowing less on the new property, lenders treat the reduction as a partial early repayment. Nationwide's terms confirm that ERCs apply on the portion of the mortgage you don't port. So if you currently owe £200,000 and only port £150,000 to a cheaper property, you'll pay an ERC on the £50,000 difference.

Typical ERCs on fixed-rate mortgages follow a declining schedule:

On a £200,000 mortgage with a 5-year fix, leaving in year one could cost £10,000 in ERCs. By year four, that drops to £4,000. If you're downsizing and only reducing your balance by £50,000, the ERC applies only to that £50,000 — so £1,000 in year four rather than £4,000.

Conversely, if you're upsizing and need to borrow more, the additional borrowing will be at your lender's current rates, not your ported rate. You'll effectively have two mortgage products running in parallel: your original balance at the ported rate, and the top-up at whatever the lender is currently offering. This is standard practice and Halifax confirms the same approach.

The arithmetic gets interesting here. If you're porting £200,000 at 2.5% and borrowing an additional £80,000 at 4.8%, your blended rate across the full £280,000 is approximately 3.16% — still well below what you'd pay on a completely new mortgage. Run the numbers for your specific situation using our mortgage affordability calculator.

Porting follows a specific sequence, and missing any step can cost you the deal.

Step 1: Tell your lender before you list your property. Contact your mortgage provider's moving home team and confirm your product is portable. Not all products are — some tracker mortgages and offset deals exclude portability. Get this in writing.

Step 2: Get a porting agreement in principle. Your lender will run a soft credit check and preliminary affordability assessment. This is not a guarantee — it's an indication that a full application is likely to succeed.

Step 3: Sell your current home and find your new one. The clock starts when your current mortgage is discharged. Nationwide gives you 180 days to complete the new purchase. Other lenders vary — some allow as little as 30 days, others up to six months. If you miss the window, your port expires and ERCs apply.

Step 4: Full application on the new property. Your lender will value the new property and conduct a full affordability assessment under current criteria. This is where ports most commonly fail. Lending criteria have tightened since 2022 — the FCA's responsible lending rules require lenders to stress-test at elevated rates, and stress tests are now run at higher rates. A borrower who qualified at 2.5% in 2023 may not qualify for the same balance today, even at the same rate, because the stress test rate has increased.

Step 5: Completion. If approved, your solicitor handles the legal transfer. You'll pay valuation and legal fees as with any mortgage, but no arrangement fee on the ported portion.

The biggest pitfall lenders won't volunteer: if you're in a chain and your purchase falls through, you may need to either extend the porting window (not always possible) or lose the port entirely. Having a backup plan — knowing what fixed deals are available — is essential.

Another consideration is whether porting actually gives you the best deal overall. If your fix is close to expiring anyway, it may make more sense to let it run out, move to SVR briefly, and remortgage at the best available rate from any lender. Porting locks you in with your current provider. Shopping the whole market might surface a better deal, especially if sub-4% rates return before your move completes.

Porting is not always the right move. Here are the situations where remortgaging fresh is the better option:

Your current rate is close to market rates. If you're on a fix at 4.5% and the best new deals are at 4.8%, the saving from porting is marginal. Factor in the hassle of a port (which can complicate your purchase timeline) and a clean remortgage may be simpler.

Your fix expires within three months. If your deal ends before or shortly after you'd complete the move, porting preserves only a few months of savings. The flexibility of choosing any lender on the market outweighs a small rate advantage.

You're significantly downsizing. If the ERC on the unpaid portion exceeds the savings from keeping your lower rate, porting costs more than it saves. Calculate the ERC on the balance reduction and compare it to the rate differential over the remaining term.

Your credit or income situation has changed. Failed porting applications don't typically affect your credit score, but they do waste time in a market where delays can cost you a property. If you know your financial position has deteriorated, apply for a new mortgage with a more flexible lender rather than risking a port rejection.

For a broader view of how to choose between fixed and variable rates when you do remortgage, see our fixed vs variable rate comparison. And for a full overview of mortgage options, visit our mortgages hub.

This article is for informational purposes only and does not constitute financial advice. You should seek independent financial advice before making any investment decisions.