Porting a Mortgage: How It Works and When It’s Worth It
If you’re moving home mid-way through a fixed rate deal, porting your mortgage lets you take your existing product across to your new property, keeping your rate and avoiding the early repayment charge that would apply if you simply broke the deal.
It sounds like a straightforward transfer, but in practice porting means a fresh mortgage application with your existing lender, and it isn’t always the cheapest option. Here, we explain how porting actually works, what can trip up an application, when it’s worth doing, and when it isn’t.
What does porting a mortgage mean?
Porting a mortgage means moving your existing mortgage product from your current property to a new one. It’s mainly used on residential mortgages, but the same principle can apply to buy-to-let.
Say you’ve got a mortgage with Barclays, three years remaining on a fixed product, and you’re looking to move. That product comes with early repayment charges (ERCs), so leaving the deal early would trigger a significant penalty. Porting is the lender’s way of letting you keep the interest rate and the product by transferring it onto the new property, while the debt on the old property is repaid, either by selling the old home, or by replacing that mortgage with a different one (for example, turning the old property into a buy-to-let).
Is porting available to everyone, or does it depend on the lender and deal?
If you’ve got an existing mortgage, porting is usually available to some degree. Most mainstream lenders will let you port a standard residential mortgage, it’s a retention feature, and having a non-portable product would be much less desirable to borrowers.
There are exceptions, though:
- Help to Buy mortgages can’t be ported
- Shared ownership mortgages sometimes aren’t portable
- Certain specialist products are non-portable by design
For most standard residential deals, porting is on the table, but it’s always worth confirming with your specific lender or a broker before you assume it.
Do you have to reapply and meet affordability criteria when porting?
Yes. Porting a mortgage isn’t a paperwork transfer, it’s effectively a whole new mortgage application with your existing lender. That means:
- A new affordability assessment
- Meeting the lender’s current criteria as of the day you apply
- A valuation on the new property
If the lender isn’t happy with the property, down-values it below their LTV limits, or you no longer meet their criteria for any reason, they can decline the port. Lenders generally don’t want to say no to existing customers, porting keeps you as a client, but there are limits to what they can flex on.
What could have changed since you took your mortgage out that might affect porting?
Quite a few things can shift between taking out a mortgage and coming back a few years later to port it.
| Residency status. If you've left the UK and come back, some lenders require a minimum period of UK residency before they'll lend again. | |
| Type of income. If you were employed when you took the original mortgage out and you've since gone self-employed with only one year of accounts, and the lender needs two, you're no longer within criteria. | |
| Credit commitments. If you've taken on significantly more credit, loans, cards, car finance, the affordability figure comes down. If you're also trying to borrow more for a bigger property, that can push the case beyond what the lender will allow. | |
| Property type. The new property might sit outside the lender's criteria even if you don't. |
There are various reasons a case can move outside criteria, so it’s worth talking it through with a broker before assuming porting will work.
If house prices have risen and you need to borrow more, how does porting work?
If you’re moving to a more expensive home and need to borrow more, the lender will look to port your existing mortgage across and, provided you pass their affordability assessment, offer you a further advance on top.
That leaves you with a two-part mortgage:
- The ported portion at your original interest rate and product end date
- The new borrowing at current market rates, with its own product end date
Both parts sit with the same lender but run separately, different interest rates, and usually different end dates.
When you first port, you often get flexibility on the mortgage term itself, so you can tweak it as part of the move (for example, extending the term if you were previously on a shorter one because you were borrowing less). Then, at the next remortgage, a good broker will try to align the two end dates so you eventually reach a point where you’re free to remortgage the whole balance without one part still being tied into an ERC.
Why do porting applications get declined?
The most common reasons a port is declined are credit changes, property type issues, and down valuations.
Credit changes. If your credit score has dropped since you took the original mortgage, missed credit card payments, unsecured loan issues, anything that fails the lender’s current credit scoring, that’s usually a blanket decline. There can be an appeals route in specific cases (for example, if something was lodged incorrectly on your file and you have evidence), but otherwise credit fails tend to be final.
Property type and down valuations. If the lender values the new property lower than the purchase price, it can push you into a higher LTV band. That in turn can move you into a lower income multiplier or push the loan outside their criteria entirely, which can mean the case no longer fits, even though nothing about you has changed.
Unless there’s a genuine appeal route, a decline usually means going to another lender.
Can the new property itself cause a porting application to fail?
Yes. Lenders set their own limits on property types and specific developments.
- New build flats or apartment complexes often have exposure caps. A lender may not want to hold more than, say, 20% of the mortgages in a single development, so if they’re at that cap, they won’t take on another one there.
- Converted properties can be declined if the lender doesn’t like the conversion or its previous use.
- Down valuations are a common cause, if the lender values the property below the purchase price, you’d need to make up the difference in deposit. If you can’t, the port typically fails.
Because so much of this hinges on the specific valuation that gets carried out once the application is in, it’s hard to predict with certainty. The reality is you often don’t know for sure until the valuation is done.
What are your options if porting is declined?
The first option is to appeal. If you’re an existing client and the decline is around something specific, a valuation number, a criteria interpretation, your broker can go back to the lender and see if there’s any wiggle room.
If there’s no appeal route, the alternative is a new mortgage with a different lender and paying the early repayment charge on your existing deal. That’s more expensive up front, but it isn’t the end of the road.
One practical approach worth mentioning: if you were planning to put a large portion of equity in as your deposit on the new property, you can sometimes reduce that deposit slightly and use the difference to cover the ERC, taking a marginally higher loan amount with a new lender. It costs more, but it can keep the move on track.
How do early repayment charges fit into the decision to port?
Porting doesn’t automatically save you money. Your broker should run a proper comparison between staying with your current lender and paying the ERC to move.
The core question is straightforward: would the monthly savings from a lower rate outweigh the ERC?
- If market rates are lower than your current rate and the saving over the remaining term is bigger than the ERC, it can be financially more sensible to pay the ERC and switch to a new lender.
- If market rates are higher than your current rate, porting keeps your existing lower rate and avoids the ERC, usually the better outcome.
Where the maths gets most interesting is when rates have dropped significantly since you took the original mortgage out and you’ve still got three or four years left on it. In that scenario, paying the ERC to obtain a much better rate can be worth doing.
What happens if your sale and purchase don’t complete on the same day?
This is very lender dependent.
- Some lenders require simultaneous completion. You have to complete your sale and purchase on the same day, or the port doesn’t happen.
- Other lenders allow a window, often three to six months, between selling your old home and buying the new one.
Where a window is allowed, the ERC is usually paid up front when you sell, then refunded when the new purchase completes within the window. So you don’t ultimately pay it, but you need the funds available for the gap.
The two options are effectively simultaneous porting or non-simultaneous porting, and which one applies depends entirely on your lender’s criteria.
When should you speak to a broker about porting?
Right at the start of the move, the same stage you’d speak to a broker on any other application, if not earlier.
Tying yourself to a specific lender’s affordability limits shapes the price range you can realistically shop in. It’s worth knowing up front:
- Can the current mortgage be ported at the price range you’re looking at?
- If it can, how much extra can the lender lend?
- If it can’t, or if the numbers don’t work, would paying the ERC and moving to a different lender give you a better outcome?
- Would it be worth adjusting the target price range instead?
Having those answers before you start viewing properties saves a lot of time and stress.
What information does a broker need to work out whether porting is the right route?
To run a proper comparison between porting, porting-and-borrowing-more, and switching to a new lender, a broker needs a clear picture of your current mortgage:
| Current mortgage balance | |
| Early repayment charge due | |
| Remaining term | |
| Current interest rate | |
| Product end date | |
That gives everything needed to work out what you’re paying now, what an ERC would cost, and whether a new deal elsewhere would beat porting once fees are factored in. Some clients are happy to give account access or share their annual statement; either way, a broker needs those numbers to give you a proper answer.
What’s the biggest mistake people make with porting?
Assuming that because a lender gave you a mortgage before, they’ll give you one now. Affordability is reassessed from scratch when you port, and if your circumstances have changed, or the lender’s criteria have, the case can fail.
That doesn’t mean you can’t move; there are usually other lending options. But it does mean paying an ERC where you can’t make up the shortfall in deposit yourself. Knowing your current affordability position before you commit to a move is the biggest single thing that protects you.
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Frequently Asked Questions
How long do I have to port my mortgage?
The window between selling your old property and completing on the new one varies by lender. Some require simultaneous completion, others allow three to six months. Your lender's specific criteria will confirm what's available.
Can I port my mortgage to a cheaper home?
Yes, you can port your mortgage when downsizing, but if you're reducing the loan amount, you may pay an early repayment charge on the portion you're paying off. That charge is usually calculated as a percentage of the balance you're not carrying across.
Can I port a mortgage from a house to a flat?
Usually yes, provided the lender is happy with the new property type. Some lenders have specific criteria around flats, particularly new builds, ex-local authority properties, or high-rise blocks, so it depends on your lender and the property.
Does porting save you money?
Not always. Porting keeps your existing rate, which is valuable if rates have risen. But if rates have fallen significantly since you took the original mortgage, paying the ERC to switch to a new lender can sometimes save you more over the remaining term. It's worth having the comparison run properly.
Do I need a solicitor to port my mortgage?
Yes. Because you're moving property, you'll need a solicitor for the sale and purchase in the usual way. Porting itself doesn't add significantly to the legal work, it's part of the wider move.
Can I port my mortgage if I've been made redundant or my income has changed?
Possibly, but it depends on the lender's current affordability rules. Because porting requires a fresh affordability assessment, income changes can affect what the lender will lend, even if you're keeping the same product.