Porting Your Mortgage When You Move Home: UK Rules for 2026

What "porting" actually means

Porting is the right, written into most fixed and tracker mortgage contracts, to take your existing mortgage deal with you when you move home. You sell your current property, repay the existing loan from the proceeds, and the lender re-advances the same amount on the same rate and terms against your new property.

The headline appeal is simple: you keep the rate you locked in, and you sidestep the early repayment charge that would normally apply if you redeemed a fixed-rate mortgage partway through its term. In 2026, with many borrowers still sitting on sub-4% deals taken out in 2021-2022, that protection is worth real money.

But porting is widely misunderstood. It is not "transferring" your mortgage in the way you transfer a phone number. Legally, your old mortgage is repaid and a new one is created — which is why the lender re-assesses you from scratch.

When porting saves you money

The clearest win is when your fixed rate is below what you could get today.

Suppose you have £220,000 left on a five-year fix at 3.9%, with two years remaining and an ERC of 3% of the balance — about £6,600. Current five-year fixes are around 4.4%. If you redeemed the loan to move, you would pay £6,600 to leave, then take a new deal at a higher rate. Porting lets you carry the 3.9% rate to the new home and pays no ERC. You win twice: no exit penalty and a cheaper ongoing rate.

The bigger your remaining balance and the longer your remaining fixed period, the more porting is worth, because both the ERC you avoid and the rate gap you preserve scale with the loan size and time left.

You can model the monthly difference between your ported rate and a fresh deal using the mortgage calculator — plug in the same balance and term at each rate and compare the monthly payment.

When a fresh deal beats porting

Porting is not always the answer. Two situations flip the maths.

Rates have fallen below your fixed rate. If you are locked at 5.4% but new five-year fixes are 4.4%, paying the ERC to escape can be cheaper over the remaining term than dragging the expensive rate to your new home. On a £200,000 balance, a one-percentage-point saving is roughly £2,000 of interest a year — which can recover a 2-3% ERC within a couple of years.

You need to borrow significantly more. Porting only carries the existing loan amount at the existing rate. Any additional borrowing for a pricier property is a separate product at current rates, decided by the lender's appetite and your affordability. You end up with a "blended" mortgage — part old rate, part new rate — and two product end-dates that may not align, which complicates your next remortgage. Sometimes a single, clean new mortgage for the whole amount is simpler and not much more expensive.

Run the comparison honestly: the ERC is a known, one-off cost; the rate difference is a recurring one. Use the remortgage calculator to see whether the interest saved by switching outweighs the penalty to leave.

The re-affordability check nobody warns you about

This is where ports fall over. Because a port is a new application, the lender applies current affordability rules — not the rules that existed when you first borrowed.

That means:

• Your income is reassessed. If you have gone self-employed, reduced your hours, gone on parental leave, or moved to a lower-paid role, you may not pass.
• Your outgoings are reassessed. New car finance, a larger childcare bill, or other credit commitments reduce how much the lender will lend.
• A stress test still applies. Lenders check you could afford payments if rates rose, so a deal that was comfortable in 2022 is not guaranteed to clear in 2026.
• Your credit file is pulled again. Missed payments or a higher credit-utilisation ratio since the original deal can count against you.

If you are declined on affordability, you cannot port — and you are stuck choosing between staying put or breaking your deal and paying the ERC. Check your numbers with the mortgage affordability calculator before you put your home on the market, so an affordability shortfall does not derail a sale.

A blunt rule of thumb: if you could not get your current mortgage approved as a brand-new application today, assume the port is at risk.

How the timing works

Porting depends on the sale and purchase lining up. Lenders handle this in two ways:

1. Simultaneous porting — the most common. You sell and buy on the same day; the old loan is repaid and the new one advanced together, with no gap.

2. Porting with a window — some lenders let you redeem first and port within a set period, commonly 3 months but sometimes up to 6. They charge the ERC on completion of the sale and refund it once you complete the new purchase within the window. Miss the window and the ERC stands.

The window matters most for chain breaks, downsizing, or moving into rented accommodation between properties. Always confirm the exact rule in writing, because "you can port" and "you can port with a six-month gap" are very different promises.

Upsizing, downsizing and the extra-borrowing trap

Upsizing. Say you port £220,000 at 3.9% but need £300,000 for the new home. The £80,000 of additional borrowing is a fresh product at, say, 4.4%. Your payment becomes a blend of the two. The risk is two different end-dates: in two years your ported rate matures while the new chunk has three years left, so your next remortgage is messy. Some lenders will "rate-match" or align the products; many will not.

Downsizing. If the new home is cheaper and you only need £150,000, you are repaying £70,000 of the ported loan. That partial repayment can trigger an ERC on the repaid portion unless it falls within your annual overpayment allowance (often 10% a year). Downsizers are frequently caught out expecting porting to be penalty-free when the reduced loan size triggers a charge.

In both cases, the cleaner the loan amount stays, the smoother the port.

A worked example

Here, porting clearly wins: you avoid a £6,600 ERC and a higher rate. Flip the rates — old deal at 5.4%, new deal at 4.4% — and the picture reverses, because the £2,200-a-year interest saving from switching recovers the ERC quickly. The lesson is that porting is a calculation, not a default.

Costs to factor in beyond the rate

Even a successful port is not free:

• Valuation fee on the new property, required because it is a new application.
• Arrangement or product fee on any additional borrowing.
• Legal and conveyancing costs, as with any move.
• Possible broker fee if you use one to manage the port and the top-up borrowing.

These are usually far smaller than an ERC, but they should be in your comparison. None of this affects your income tax position — porting is a borrowing decision, not a taxable event — but if you are juggling a move alongside changes to your pay, it is worth sanity-checking your monthly budget with the take-home pay calculator so the new mortgage payment fits your actual net income.

Practical checklist before you rely on porting

• Confirm in writing that your specific product is portable — most are, but some specialist and older deals are not.
• Ask for the exact ERC and the precise porting window (same-day only, or a gap allowed).
• Get an affordability decision in principle for the port before listing your home.
• Price up the additional borrowing separately so you see the blended payment.
• Compare porting against breaking the deal and remortgaging when current rates are below your fixed rate.
• Check whether downsizing triggers a partial-repayment ERC.

Try the numbers for your own move

Related reading:

• 2-year fix vs 5-year fix mortgage 2026
• How much mortgage can I get on £40k salary in 2026
• Mortgage overpayment vs investing

Sources

• FCA: Mortgage conduct of business and porting rules
• UK Finance: Mortgage market data and guidance
• MoneyHelper: Porting your mortgage
• gov.uk: Early repayment charges and mortgage terms