Porting Your Mortgage vs. Starting Again: What Really Happens When You Move

Moving home is rarely just about the new property. One of the biggest financial decisions sits with the mortgage you already have, and specifically what you do with it when you move.

Broadly, you have two routes: take your existing mortgage with you, known as porting, or redeem it and start afresh with a completely new loan. Neither is automatically the right answer.

The best choice depends on the rate you are currently on, whether any early repayment charges apply, how much you need to borrow for the new property, and what is available in the wider market at the time you move.

This article walks through both options so you can understand the trade-offs, and explains what porting actually is, because it is widely misunderstood, even by people who have done it.

Option one: a completely new mortgage with a new lender

The simplest way to think about moving home is to treat it as a clean slate.

You redeem the mortgage on your current property when you sell, and you arrange a brand new mortgage with whichever lender offers the best terms for your new home. Your existing lender is paid off in full and steps out of the picture entirely.

In many cases this is the most cost-effective route, particularly where there are no early repayment charges on your existing loan.

If you are outside your fixed or discounted period, or on a lender’s standard variable rate, there is usually nothing stopping you from simply choosing the sharpest deal available and moving your borrowing across to it.

You are not tied to your current lender’s pricing, criteria or product range, so you have the whole of the market to aim at.

What about early repayment charges?

It is easy to assume that an early repayment charge, or ERC, automatically rules out taking a new loan elsewhere.

It does not. An ERC is a cost, but it is only one cost among several, and sometimes the maths still favours redeeming the existing loan and paying the charge. If a new lender is offering a materially lower rate, the interest you save over the new deal can outweigh the ERC you pay to leave, especially on a larger loan or a longer fixed term.

The key point is that an ERC should be weighed, not feared.

The right way to approach it is to compare the total cost of staying and porting against the total cost of leaving, ERC included, over a like-for-like period. On the right numbers, paying an early repayment charge and moving to a lower rate can genuinely be the cheaper outcome. This is precisely the kind of calculation a broker is well placed to run for you, because the answer is rarely obvious from the headline rate alone.

Option two: porting your existing mortgage

Porting means transferring your current mortgage deal, and specifically your current interest rate, from your old property to your new one.

If you have a competitive rate that you would struggle to replace in today’s market, or you are locked into a deal with early repayment charges, porting can be very attractive. It lets you keep the terms you already have rather than surrendering them.

Why porting can be the smart move

• You keep a great rate. If you secured your mortgage when pricing was lower than it is now, that rate is worth protecting. Porting lets you carry it over to the new property instead of losing it.
• You may avoid early repayment charges. Because porting is generally treated as a continuation of your existing deal rather than a redemption, lenders will usually waive the ERC that would otherwise apply when you move within the required timeframe.
• Continuity and certainty. You stay with a lender you already know, on terms you already understand, which can make the process feel more straightforward.

How porting actually works

Here is the part that surprises most people.

Porting is not the same as simply picking up your mortgage and carrying it, unchanged, to a new house.

In reality, your existing loan is redeemed (paid back) and a new mortgage is taken out. What the lender allows you to do is take your existing rate, or product, with you and apply it to the new borrowing, rather than losing it.

In other words, porting is a fresh mortgage application against the new property, assessed under the lender’s current criteria and affordability rules, but with your existing interest rate transferred across so you keep the rate and, typically, avoid the early repayment charge.

It is best understood as a new mortgage that carries your old rate, not an old mortgage that simply follows you.

Topping up when you need to borrow more

Most people who move are buying a more expensive property and therefore need to borrow more than their existing loan. Porting handles this through a top-up.

You carry your existing balance across on its current rate, and you borrow the additional amount you need on one of the lender’s other products, usually a current deal from their live range. The result is a mortgage made up of more than one part: your ported balance on your original rate, plus the top-up on a separate, current rate.

This has a few practical consequences worth understanding:

• Two products, two end dates. Your ported portion and your top-up may run to different end dates, which can mean they come up for renewal at different times unless you take steps to align them.
• The top-up is priced today. The additional borrowing is charged at whatever rate the lender currently offers, so the blended cost of your overall mortgage depends on both parts, not just the rate you are trying to protect.
• Affordability is assessed on the whole loan. The lender assesses affordability across both the ported balance and the top-up combined, not just the extra you are borrowing. This matters because it is entirely possible for a lender to agree to port your existing loan yet decline to advance the full top-up you need, if the total does not sit within what their current affordability rules allow. In that situation you may be able to port and borrow a smaller top-up, but not the whole amount you were hoping for.
• It is still a full application. Because porting is a new mortgage, you must pass the lender’s current affordability and criteria checks. Porting is not guaranteed simply because you were approved before, and circumstances such as a change in income can affect the outcome.

Related case study: Protecting a Sub-2% Rate on a Home Move: Porting and Topping Up With the Same Lender

So which route is right for you?

There is no single answer, and that is the honest position.

If you hold a strong rate and face early repayment charges, porting will often be the sensible choice, letting you protect your deal and top up for the extra you need. If your existing rate is unremarkable, or the ERC is small, or a new lender is offering something markedly better, a completely new mortgage may leave you better off overall, even after accounting for the cost of leaving.

What matters is comparing the true total cost of each route over a comparable period, rather than reacting to a single figure such as an ERC or a headline rate.

That comparison needs to take in your ported rate, the cost of any top-up, product and arrangement fees, and how long you expect to hold the mortgage before reviewing it again.