Porting Your Mortgage

"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, but in practice only about a third of movers actually port successfully. 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% two years ago and current rates are 4.8%, porting keeps the cheap rate on the portion you're taking forward. 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 3.5% fixed for 3 more years. You need £250,000 for the new property. The £180,000 stays at 3.5%; the new £70,000 is at, say, 4.8% 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.

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, shop the whole market

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 3.5% fixed, 3 years left. ERC: 3% = £6,000. New property needs £280,000 mortgage.

Option 1 — Port + top-up:

£200,000 at 3.5% (ported, 3 years remaining)
£80,000 at 4.6% (new 3 year fix)
Blended rate ~3.8%
Total monthly payment: lower than market by ~£100

Option 2 — Redeem + new £280k at 4.6%:

Pay £6,000 ERC now
All £280,000 at 4.6% for 5 years
Clean single product

Over 3 years, Option 1 saves roughly £3,600 in interest vs Option 2, minus the slightly lower rate on your new fix → net benefit of porting might be £2,000–£3,000. Worth checking the math carefully.

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 sale and purchase to port (typically 1-90 days)
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 make portability smooth (generally speaking): 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, most portable mortgages give you a grace period:

Sale before purchase (buying a new place later): 1-90 days of grace to port your mortgage onto a new property. You'll temporarily pay off the old mortgage and potentially live in rented accommodation. The ERC is usually refunded at the point of porting, not at the point of sale.
Purchase before sale (buying before selling): rarely compatible with porting. You'd effectively have two mortgages simultaneously, and the ported product goes on the new property. Most lenders require a sale to complete within 90 days.
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, though it's less common. You'd port a smaller mortgage (or the same mortgage) to the new property. If you're releasing equity by downsizing, you'd reduce the mortgage and potentially just port a portion. 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 when the port completes — often within 14-28 days. Get this in writing from the lender upfront.

Can I port a tracker or variable mortgage?

Tracker and SVR products don't usually have ERCs, so porting is less relevant — you can just redeem and take any new product without penalty. 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.

Written by a CeMAP qualified mortgage advisor

Last updated: April 2026