Porting a Mortgage to a New House: How It Works

What is porting a mortgage? Porting a mortgage means taking your existing mortgage rate, lender, and terms with you to a new property — avoiding an Early Repayment Charge that can run to £6,000-£8,000, and skipping a full remortgage. It works best when your current rate beats today's market, but porting isn't automatic: you must requalify under today's affordability rules and the new property must suit the lender.

"Porting" means taking your existing mortgage product with you when you move home — keeping the same rate, lender, and terms, avoiding early repayment charges, and skipping a full remortgage. Most UK residential mortgages are portable in principle, but porting is not a formality in practice: you have to pass a fresh affordability assessment and the lender has to accept the new property, so a meaningful number of attempted ports fall away. This guide covers when porting works, when it doesn't, and how it compares to taking a new product.

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What Porting Actually Means

Porting is a conditional transfer of your mortgage from one property to another:

You keep your existing rate, product, and remaining term
You avoid the Early Repayment Charge (ERC) on your current fix
You apply afresh for the new property — the lender re-assesses your affordability and the property
The new mortgage is legally a new agreement, but the rate and product are inherited

It's called "porting" because the mortgage is technically redeemed (paid off) on completion of your sale and a new one issued on completion of your purchase, usually within the same day. The lender refunds your ERC (or never charges it) because the redemption and new lending happen simultaneously.

When Porting Makes Sense

You're mid-fix and the ERC would be painful

If you're 2 years into a 5-year fix and moving, the ERC might be 3-4% of the outstanding balance. On a £200,000 mortgage, that's £6,000–£8,000. Porting avoids the fee and keeps your fixed rate.

Your existing rate is better than current market rates

If you fixed at 3.5% back in 2022, porting keeps that cheap rate on the portion you're taking forward. Today's best-buy fixes start at about 4.9–5.1% for borrowers with a large deposit, and the average two-year and five-year fixes are 5.98% and 6% (checked 5 October 2026). This is the biggest genuine benefit.

You don't want the hassle of a new lender

Staying with your current lender skips the full application with a new bank — valuation, underwriting, and product selection all run faster because the lender already knows you.

When Porting Doesn't Work Well

You need to borrow significantly more

Porting lets you borrow more, but the additional borrowing is a separate loan at current rates — not the ported rate. If the extra is substantial, you end up with a hybrid:

Portion 1: original mortgage at original rate (ported)
Portion 2: top-up mortgage at current rate

Example: your current mortgage is £180,000 at 5% fixed for 3 more years. You need £250,000 for the new property. The £180,000 stays at 5%; the new £70,000 is at today's rates, say 6%, for 2 or 5 years. Two separate end-of-fix dates, two separate products, slightly messier admin.

Your circumstances have worsened

The lender reassesses affordability for the new property. If your income has dropped, you've taken on debt, your credit score has fallen, or the new property is harder to value, they can decline the port.

The new property is unsuitable for the lender

Some lenders won't lend on specific property types (non-standard construction, certain flat types, above commercial premises). If your current lender refuses the new property, portability fails — even if your finances are fine.

You've been late on payments

Some missed payments on the existing mortgage can void portability. Lenders are within their rights to decline a port if your payment history is poor.

You're downsizing significantly

Porting is designed for similar-or-larger purchases. Downsizing to a property where you only need a small mortgage may not be worth porting — a small ported mortgage at the old rate vs a small new mortgage at current rates rarely moves the needle financially, and the product may have a minimum loan size. Bear in mind that the ERC still applies to whatever you pay off rather than port. Two years into a 5-year fix, porting £100,000 of a £200,000 balance could leave an ERC of roughly £3,000–£4,000 on the other £100,000 (for example 4% in year 2 at Nationwide, reduced by any unused overpayment allowance). Ask your lender for a figure before you decide.

Porting vs Taking a New Product

Always check the numbers

Before assuming you'll port, compare three options:

Port + top-up — current rate on the ported portion, current rates on the top-up
Redeem + new product — pay the ERC, take a whole new mortgage at current rates
Remortgage to a different lender entirely — pay the ERC, choose from other lenders

Your broker can model all three. The right answer depends on:

Current ERC amount
Gap between your original rate and current market rates
Remaining term on your current fix
How much you need to borrow
Whether other lenders offer better rates for your new situation

Worked example

Current: £200,000 at 5.2% fixed, 3 years left. ERC: 3% = £6,000. New property needs a £280,000 mortgage, and new borrowing costs about 6%. The figures assume a 25-year repayment term and are illustrative.

Option 1 — Port + top-up:

£200,000 at 5.2% (ported, 3 years remaining)
£80,000 top-up at 6% (a new fix from the same lender)
Blended rate about 5.4%
Monthly payment about £1,710
No ERC to pay

Option 2 — Redeem + new £280k at 6%:

Pay the £6,000 ERC now
All £280,000 at 6% for 5 years
Monthly payment about £1,805
Clean single product

Over the 3 years left on the old fix, Option 1 costs about £4,800 less in interest (about £133 a month), and the monthly payment is about £95 lower. Add the £6,000 ERC you don't pay, and porting comes out about £10,800 ahead before fees. A top-up and a new deal usually both carry an arrangement fee, so compare those too.

Two things can shrink that lead. The ported part needs a new deal after 3 years, at whatever rates apply then, while Option 2 stays fixed for 2 more years. And a new deal well below 6% cuts the interest saving: with a large deposit, best buys start at about 4.9–5.1%, and at those rates the ERC you avoid is most of the benefit. Your broker can run the numbers on your own figures.

The Porting Application Process

Even though porting "inherits" your product, you still go through a full application:

Tell your lender you want to port — they'll check portability in principle
Submit a new application with updated income, employment, outgoings
Property valuation on the new purchase (same as any mortgage)
Underwriter review — new property + updated circumstances
Lender issues a new mortgage offer (often called a "porting offer" or "portable product offer")
Simultaneous redemption and new lending — your sale completes, old mortgage redeemed, new mortgage funded on the new property

The new application reassesses you at current criteria. Lenders can tighten criteria between when you first took the mortgage and when you port — so what was acceptable then may be harder now.

Portability Rules to Check on Your Existing Product

Read your current mortgage offer document for the specific porting terms. Look for:

ERC refund window: how long you have between repaying the old mortgage and completing the new one (typically 3–6 months; some lenders, such as Halifax, only port on a same-day completion)
Specific conditions — some products exclude porting to BTL or specific property types
Top-up rate — what rate applies to any additional borrowing
Affordability reassessment — whether the lender will re-stress at current rates
Minimum / maximum loan — some products have floors and ceilings

Lenders that generally make portability smooth when your sale and purchase complete on the same day: Nationwide, Halifax, Santander, HSBC, Barclays, NatWest. Smaller building societies and specialist lenders vary more.

If Your Timing Misaligns

Ideally your sale and purchase complete on the same day. If they don't, many lenders give you a window:

Sale before purchase (buying a new place later): many lenders still let you port, as long as the new mortgage completes within a set time after the old one is repaid. This is typically 3 to 6 months: for example 3 months at Santander, 4 months at NatWest and 6 months at HSBC and Nationwide. You pay the ERC when the old mortgage is repaid and get it back once the new one completes. Not every lender ports in this situation. Halifax only ports when the sale and purchase complete on the same day. If you sell first, you choose a new product at today's rates, and the ERC is refunded only if you apply for a new Halifax mortgage within 3 months. Some lenders handle these ports only directly, not through a broker (HSBC, for example). Check your own lender's terms before you sell.
Purchase before sale (buying before selling): your current deal normally can't move to the new home while your old mortgage is still running, because porting needs the old mortgage to be paid off. If you buy first, the new home usually needs a new mortgage or bridging, and the lender will test affordability with both mortgage payments. There are two ways you may still keep your rate. 1) Pay off your current mortgage on the day you buy, from savings or by remortgaging your current home with another lender. NatWest and HSBC accept this. 2) Buy with bridging, then port onto the new home when your old one sells. Only some lenders allow this: Nationwide will port onto a home you already own if it's done on the day your old mortgage is paid off, and Virgin Money will within 3 months. Barclays won't port onto a home you already own. Check your lender's rules before you commit.
Bridging: some lenders will work with bridging finance during the gap, but this is messy and expensive.

Frequently Asked Questions

Can I port my mortgage to a more expensive property?

Yes. You can port the existing loan and take top-up borrowing at current rates for the additional amount. The ported portion keeps its original rate; the top-up is a new sub-account at current rates. This is the most common porting scenario.

Can I port to a cheaper property?

Yes. You port the amount you still need and use your sale proceeds to pay off the rest. The catch is that the part you pay off usually counts as an early repayment, so an ERC is charged on it while you're in a fixed or discounted deal. Most lenders charge it in proportion to the balance you don't port (Halifax, Santander, HSBC; HSBC takes the full ERC and refunds the ported share after completion). Some let any unused annual overpayment allowance reduce it (Nationwide, NatWest), and Barclays charges nothing if you cut the balance by up to 25%. Compare that cost with paying the full ERC and taking a new deal. Check minimum loan sizes on the existing product.

Do I have to port?

No — porting is optional. You can pay the ERC and take a new product with the same or a different lender. Always compare both options.

How long does porting take?

Typically 2-6 weeks, similar to a normal mortgage application. Sale and purchase must align to allow simultaneous redemption and new lending. Some lenders are faster than others.

Is porting guaranteed?

No. Portability is a right to apply, not a right to be approved. The lender reassesses you and the property. If either fails (affordability, property type, credit changes), they can decline the port.

What's the ERC refund process?

When sale and purchase complete on the same day, the ERC is usually refunded at that moment (the funds never actually leave). When timing misaligns, you pay the ERC at redemption and the lender refunds it once the new mortgage completes, provided you're within its window. The refund often takes 14-28 days. Get this in writing from the lender upfront.

Can I port a tracker or variable mortgage?

SVRs don't have ERCs, and many trackers don't either, so you can often redeem and take a new product without a penalty. But some trackers charge an ERC in their initial period (for example NatWest 0.5% or 0.25%, Principality 1%, and up to 3% at some building societies), and most discounted-variable deals do. Check the ERC section of your offer before you redeem. If your current tracker is below current market rates, porting still makes sense to preserve the margin.

Can I port from a residential to a BTL?

Almost never. Porting is typically restricted to the same product category (residential to residential). If you're converting a residential property to a BTL and buying a new residence, you'd usually remortgage the BTL separately and take a new residential mortgage on the new home.

Reviewed by Phillip Wakeling-Smith (CeMAP) — Mortgage Adviser. About the author.

Last reviewed: October 2026