Porting means carrying your existing mortgage and its interest rate across to a new property. Most mortgages allow it. It protects a good rate and avoids early repayment charges — but it is not automatic, and it fails more often than people expect.
What actually happens
Porting sounds like the mortgage moves with you. Legally, it does not.
Your existing mortgage is repaid when you sell, and a new one is issued on the new property — with the same product applied to it. Same rate, same end date, same terms.
That distinction matters, because it means you make a fresh application. Your income is reassessed. The new property is valued and must be acceptable to the lender. If either fails, the port fails, even though nothing about your existing mortgage has changed.
When porting is clearly worth it
Your current rate is better than anything available now. If you fixed at a low rate and rates have since risen, that deal is worth real money. Porting keeps it.
Leaving early would trigger a large early repayment charge. Porting normally avoids the charge entirely, provided the sale and purchase complete simultaneously or within the lender's permitted window.
Your circumstances have not changed. Same job, same income, similar borrowing.
The four ways porting fails
1. The new property is unacceptable. Your lender must approve the new house. A flat above a shop, non-standard construction, a short lease, or a property with a large plot or annexe can all be declined — and if your lender says no, you cannot port, regardless of your rate or your income.
2. You fail affordability. This is the one that surprises people most. Being an existing borrower earns you nothing. Childcare costs, car finance, a change to self employment or a mortgage running past retirement can all reduce what the lender will now offer. If you need to borrow more and fail on the larger amount, some lenders will not let you port at all.
3. The timing does not line up. Porting usually requires the sale and purchase to complete on the same day, or within a permitted window afterwards — commonly up to three months, sometimes six. If your sale completes and your purchase is delayed beyond that window, the port lapses and you lose the rate.
4. You are borrowing substantially more. You can normally port and add borrowing, but the extra is taken at today's rates as a separate sub-account. You end up with two parts of one mortgage on different rates ending on different dates, which complicates every future remortgage.
Porting down
Less discussed, and relevant to anyone moving somewhere cheaper.
If your new mortgage is smaller than your current one, you are repaying part of the balance — which can trigger an early repayment charge on the portion repaid, even though you have ported the rest.
Some lenders allow a reduction without penalty. Others do not. Check before you agree a sale price, particularly if you are downsizing.
Porting and the second sub-account
Worth understanding properly, because it shapes every remortgage you do afterwards.
When you port and borrow more, you end up with two parts to one mortgage. The ported portion keeps your original rate and original end date. The additional borrowing sits alongside it on a current rate, with its own end date — often two or five years from the move.
The practical consequence arrives later. When the first part's deal ends, you can only remortgage the whole mortgage away if you are willing to break the second part early and pay its early repayment charge, or wait until both align.
Lenders will often let you choose the term on the additional borrowing so that both parts end on the same date. Ask for this specifically at the point of application. It is easy to arrange at the outset and awkward to fix afterwards, and it is not usually offered unprompted.
If you expect to borrow a substantial amount more, this is one of the stronger arguments for a full remortgage instead — one mortgage, one rate, one end date.
What to do first
Before you list your house:
- Ask your lender whether your product is portable and get it in writing. Most are; some are not
- Ask what the early repayment charge would be if you did not port
- Ask what the completion window is if the sale and purchase do not align
- Have your affordability checked on the new borrowing amount
That is a short conversation and it prevents the expensive version of this problem — discovering the port has failed after you have exchanged.
Porting is not automatically the answer
If your existing rate is unremarkable, a full remortgage to a new lender opens the whole market and gives you one clean mortgage on one end date. We compare both, including all fees, and show you the actual difference rather than the headline one.
Call 0116 277 7536 or see home mover mortgages in Leicester.
More guides: moving home guides for Leicester.
