Porting your mortgage: What it means and when it’s worth doing
If you are partway through a fixed-rate mortgage deal and thinking about moving home, one of the first questions worth asking is whether you can take that mortgage with you. In most cases, the answer is yes. The process is called porting, and when the circumstances are right it can save a meaningful amount of money. When the circumstances are not right, it can add unnecessary complexity to an already busy transaction. Understanding which situation you are in is what makes porting a decision rather than a default.

What porting actually means
Porting a mortgage means transferring your existing mortgage product, specifically the interest rate and its terms, from your current property to the new one you are buying. You are not literally moving the mortgage loan. The original loan is redeemed when your current property sells, and a new loan is created on the new property at the same rate and terms.

This is an important distinction because it means porting is not automatic. Even if your mortgage is described as portable in your original offer document, you still need to reapply to your lender and pass a full affordability assessment against your current income, outgoings, and financial position. The lender will also assess the new property. If your circumstances have changed since you took out the original mortgage, or if the new property does not meet the lender’s lending criteria, the port can be declined even if the existing mortgage has been running perfectly well.

Why porting matters: the early repayment charge
The primary reason borrowers choose to port rather than simply redeeming their existing mortgage and taking a new one is to avoid an Early Repayment Charge. Most fixed-rate mortgages carry an ERC for leaving the deal before the end of the fixed term. These charges are expressed as a percentage of the outstanding mortgage balance and can represent several thousand pounds depending on the balance and the deal structure. By porting the mortgage to the new property rather than exiting the deal, the ERC is avoided.

The ERC is not a penalty for doing something wrong. It is the mechanism by which lenders recover the expected income from a fixed-rate deal when a borrower exits early. The calculation of whether porting is worthwhile therefore begins with how large the ERC would be if you did not port, and how much of the fixed term remains.

Some lenders charge the ERC when your current mortgage is repaid and refund it once the port completes on your new home, provided this happens within their set timeframe. It is worth checking how your lender handles this.

When porting is worth doing
Porting makes the most financial sense when you are mid-way through a fixed-rate deal with a meaningful ERC still to run, and when your current rate is noticeably lower than what is currently available in the market. If you fixed at a rate two or three years ago that is below what you could achieve on a new deal today, taking that rate with you to your next property has real financial value across the remaining term.

It is most straightforward when the new property costs a similar amount to the one you are leaving, so the amount you need to borrow remains broadly the same.

When you need to borrow more
If you are moving to a more expensive property and need to increase your borrowing, the additional amount above your existing balance is typically taken out as a separate new product at the lender’s current rates. This creates what is sometimes described as a two-part mortgage, where the ported balance sits at the old rate and the top-up sits at the new rate. The two parts may have different terms and different end dates, which adds some complexity to future product decisions. A mortgage adviser can model the combined monthly cost of both parts against the alternative of taking an entirely new mortgage at current rates on the full amount needed.

When porting is less likely to be worth it
If your existing deal has less than six months to run, the ERC is usually lower and the ported rate would only apply for a short time, so the value of porting is reduced. If current market rates are similar to or better than your existing rate, the financial case for protecting that rate weakens. If you are downsizing to a significantly cheaper property, paying off the difference between your ported balance and the new property price may trigger a partial ERC on the amount being repaid, which can offset the saving from porting the remainder.

The practical steps
If you are considering porting, tell your lender early in the process. Most lenders have a porting window, typically a few months, within which the transfer needs to complete. Check whether your mortgage offer document explicitly describes the mortgage as portable. Work with a mortgage adviser to run the comparison between porting and taking a new product in full, accounting for all fees and rates across the remaining term.

Talk to our team about your mortgage options when moving