Mortgage Porting Explained — Moving House Without Losing Your Rate 2026/27
How porting a mortgage works when moving house in the UK, when it saves on early repayment charges, and what happens if you need to borrow more for 2026/27.
Why Porting Exists
Most fixed and tracker mortgage deals carry an early repayment charge (ERC) if you pay them off before the deal ends, which would otherwise apply if you simply cleared the mortgage on your old property when moving house. Porting lets you avoid that charge by carrying the existing deal across to the new property — technically the old mortgage is redeemed and a new one begins, but because it happens as part of an agreed porting process with the same lender, the ERC is waived.
The Affordability Check You Still Have to Pass
A common misconception is that because you already have the mortgage, porting is simply a formality. In practice, your lender re-runs a full affordability assessment against current lending criteria and your current financial circumstances — income, outgoings, existing debts and credit history — exactly as if you were a new applicant. If your income has fallen, your debts have increased, or lending rules have tightened since you first took out the mortgage, you could be declined for porting even on a rate you've held for years without issue.
Splitting the Mortgage When You Need to Borrow More
| Scenario | What happens to the rate |
|---|---|
| New property costs the same or less | Full amount ported at your existing rate |
| New property costs more, extra borrowing needed | Ported portion keeps existing rate; extra amount is a new mortgage at current rates |
| Porting declined at affordability check | Full new mortgage required, existing deal's ERC may apply |
Where extra borrowing is needed, most lenders offer it as an additional sub-account within the same overall mortgage, at whatever rate is currently available, rather than blending the two into one rate. Your monthly payment calculation then needs to account for both portions separately — the ported balance at the old rate and the top-up at the new rate — rather than assuming the whole thing stays at the rate you're used to.
When a Fresh Remortgage Beats Porting
Porting is most valuable when your existing rate is meaningfully below what's currently available in the market and a reasonable amount of the fixed period remains, since that's precisely the scenario where an ERC would otherwise bite hardest. If your deal is close to its natural end anyway, or current market rates have fallen below your existing rate, the ERC-avoidance benefit of porting shrinks or disappears, and a full remortgage — shopping the whole market rather than being tied to your existing lender's porting terms — is likely to work out better.
Steps Before You Commit to Porting
- Check the remaining early repayment charge on your current deal and how it compares to porting fees or a new remortgage
- Get an informal affordability assessment from your current lender before relying on porting in your house move plans
- If borrowing more, ask what rate would apply to the additional amount
- Compare the blended cost of porting plus a top-up against a full remortgage to a new lender
Use the mortgage calculator below to model your new monthly payment, and the remortgage calculator to compare porting against switching to a new lender.
Frequently asked questions
What does it mean to port a mortgage?
Porting means taking your existing mortgage deal — the same interest rate and remaining term — with you when you move to a new property, rather than repaying it and taking out a fresh mortgage. It effectively ends the old mortgage and starts a new one secured against the new property, but keeps the same rate, avoiding an early repayment charge that would otherwise apply if you simply paid off the mortgage early.
Do I need to pass a new affordability check to port my mortgage?
Yes — porting is not automatic. Your lender will reassess your income, expenditure and credit profile against current lending criteria as though you were a new applicant, even though you're keeping the same rate. If your circumstances have changed since you first borrowed (lower income, more existing debt, self-employment instead of salaried work), you might not pass the new assessment even on a rate you already had.
What happens if the new property costs more and I need to borrow extra?
The ported portion of your loan keeps your existing rate, but any additional borrowing needed for the more expensive property is usually arranged as a separate new mortgage product at current rates, often with your same lender. This means you can end up with two parts to your mortgage — the ported original rate and a new-rate top-up — which is worth factoring into your monthly payment calculations rather than assuming the whole loan stays at the old rate.
Is porting always cheaper than a full remortgage?
Not necessarily — it depends on how far below current market rates your existing deal is, and what remains of any early repayment charge period. If your fixed rate is close to ending anyway, or if current market rates are lower than your existing deal, a fresh remortgage to a new lender may work out better than porting, despite the early repayment charge you'd otherwise avoid by porting.
Try the calculators
Related reading
Offset Mortgage vs a Savings Account — Which Saves More in 2026/27?
How an offset mortgage compares to keeping savings in an easy-access account or Cash ISA once savings interest tax is factored in for 2026/27.
Your Fixed Rate Is Ending — A UK Remortgaging Checklist for 2026/27
What to do in the six months before your fixed-rate mortgage deal ends, including the standard variable rate trap and how to compare a product transfer against a full remortgage.
Guarantor Mortgages 2026: How They Work, Risks, and Getting Released
Guarantor mortgages help first-time buyers with insufficient income or deposit get on the ladder. Here's how they work, what the guarantor risks, and how they compare to JBSP mortgages.