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Porting is worth it when the early repayment charge on your current product is large, or the rate on it is cheaper than anything you could get today, and you pass the lender’s affordability test again. If none of those apply, paying the charge and taking a new mortgage is often simpler and sometimes cheaper.
The word “porting” makes it sound like you carry the mortgage with you. You do not. What moves is the product, meaning the rate, the remaining fixed period and the early repayment charge schedule. The loan itself is repaid on the sale of your old home and a brand new loan is set up on the new one, with a full application and a fresh affordability assessment.
Is porting a mortgage a new application?
Yes. The lender treats a port exactly as it would treat a new customer. You submit payslips, bank statements and a credit search, the new property is valued, and the underwriter checks the loan fits their current criteria. The only difference from a normal purchase is that the product terms are carried across instead of being chosen from today’s range.
That matters because your circumstances may have changed since the original mortgage. A new baby, a lower salary, a car loan or a self-employed year all feed into the new test. Passing it four years ago does not mean passing it now.
Which lenders allow porting?
Most mainstream residential products are portable in principle, but “portable” only means the lender will consider it. It is a feature of the product, written into the offer, and it does not oblige the lender to approve the new loan.
Porting moves the product, not the loan, and is a full new application with a fresh affordability test
It helps most when the early repayment charge is large or the current product is cheaper than today's market
The usual failures are a failed re-test, a gap between sale and purchase, or a declined property
When does porting a mortgage save money?
The comparison is always the same. On one side is the cost of leaving: the early repayment charge on your current product plus the cost of a new product on the full loan. On the other is the cost of staying: any product fee the lender charges on the ported loan plus a second product on any extra borrowing.
Take a £250,000 balance with two years left on a five-year fix and a 3% early repayment charge in year three. Leaving costs £7,500 before you have paid a penny of the new product’s arrangement fee. If the rate on your existing product is also lower than the rate on a comparable new product today, the saving on interest over the remaining two years sits on top of that £7,500. In that case porting is very often the cheaper route, provided the new application is approved.
Now change one thing. Suppose the fix ends in four months. The charge may have stepped down to 1%, or £2,500, and you would only be porting a product that expires almost immediately. Then a new mortgage arranged to start on completion, with the charge paid from sale proceeds, can cost less in total and gives you one clean loan on one end date. My early repayment charges article covers how the schedules step down.
Timing also drives it. If the fix is ending within the lender’s window, often three to six months, you may be able to switch to a new product on completion without any charge at all, which removes the reason to port.
The third factor is the size of the new loan. If you are moving up and need £80,000 more, that £80,000 goes on a separate product from the lender’s current range. You end up with two products, two rates and two end dates. The saving from porting the original £250,000 still applies, but the extra borrowing is priced at today’s market and the lender’s criteria decide whether they will lend it at all. The pages on moving home mortgages go through the top-up mechanics.
What goes wrong when porting a mortgage?
Four things go wrong most often.
The affordability re-test fails. This is the most common. Lenders’ affordability models have changed since 2022, and a loan approved on the old model may not pass on the new one, even with no change to your income. The result is a lower maximum than the balance you wanted to carry, and the shortfall has to come from deposit or the port collapses.
The sale and purchase do not line up. Porting assumes you redeem the old loan and draw the new one on the same day, or close to it. Most lenders allow a window, commonly 30 to 90 days, to complete the purchase after the sale. Sell first and rent for six months and the window closes, the early repayment charge is taken on redemption and, at best, refunded if you complete within the window. Outside it the charge is gone.
Two end dates. Any top-up borrowing sits on a different product with its own fixed period and its own charge schedule. When the original product ends you remortgage that part, but the top-up may still be inside its penalty period, which limits you to the same lender’s product transfer range at that point.
The property is declined. A flat above a shop, a non-standard construction, a short lease or a low valuation can all fail the lender’s property criteria, and the product cannot be ported to something the lender will not lend on. The charge then applies in full unless another product with the same lender fits.
What I see in practice
Every port I have handled has turned on two things, in this order: the valuation of the property being bought, then the affordability re-test. Until the valuation is back you do not know how much you are porting or whether a top-up is needed, so I do not let a client rely on porting until both have come through.
Speak to an expert
If you are thinking of moving before your fix ends, send me your current mortgage offer and the price you are looking at and I will show you the port against a fresh mortgage, side by side.
What are the alternatives to porting?
Pay the charge and start again. If the charge is small relative to the loan, a new mortgage from the whole market on one product with one end date is simpler and can be cheaper. The charge is paid from sale proceeds and the new lender never needs to know about the old product.
Wait. If your fix ends within a few months, completing after the end date removes the charge entirely, and you take the new mortgage at whatever the market offers then. Moving dates are hard to control, but a seller who will accept a slower completion changes the arithmetic.
Port part of the loan. Some lenders will let you port a smaller balance than the original, paying the charge only on the portion you repay. That suits people downsizing with a large charge.
Stay put and remortgage instead. If the move was partly about releasing money, a remortgage on your current home may do the job without a purchase at all.
Before any of these, ask your current lender three things: is the product portable, what is the charge today and on what date does it step down, and what is their window between sale and purchase. Those three answers decide most cases before an application is needed. Which route suits you comes down to the size of the charge, the time left on the fix and whether the new loan passes affordability.
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