Porting a mortgage: taking your deal to a new home
Porting means taking your existing mortgage deal, at its current rate, to a new property when you move, instead of repaying it and starting again. It is a fresh application to your existing lender, so they must accept the new home and reassess your affordability; portability is not guaranteed even on a portable product. If you borrow more, the extra is usually a top-up at today's rates, giving a blended cost. Porting is most valuable when your existing rate is low or leaving would trigger an early repayment charge.
How porting actually works
Despite the name, nothing physically moves. When you port, you repay the mortgage on your old home as it sells and, on the same day, your lender advances the same deal against your new home. In practice it is a new application: the lender values the new property, checks it is suitable security, and reassesses your income and outgoings under today\'s rules. If all of that passes, you keep your existing rate and terms on the balance you carry over. If it does not, the port can be declined even though the product was portable.
Borrowing more, or needing less
Moving up usually means borrowing more. The extra is normally a separate top-up at a current-day rate, sitting alongside your ported balance, so you end up with two parts on one mortgage and a blended overall cost. Our porting calculator works that blend out. Moving down, or putting in a big deposit, can mean carrying less than your current balance; repaying part of it may trigger an early repayment charge on the amount you drop, so check that before you commit.
When porting is worth protecting
- Your rate is much lower than today\'s. Keeping a cheap fix through a move can be worth a lot.
- Leaving would trigger an ERC. Porting can carry the deal across without the charge, if the lender allows it.
- Your circumstances have changed. If your income is now harder to prove, staying with a lender that already knows you can be simpler, though affordability is still reassessed.
When a fresh remortgage may beat porting
Porting is not automatically best. If your existing rate is unremarkable, if you need to borrow substantially more, or if another lender is simply cheaper across the whole balance, a full remortgage can win. The honest comparison is the total cost of porting plus the top-up against the total cost of a new deal on the whole amount, including any early repayment charge. A regulated broker can run both and tell you which is better for your move. We introduce you to one.
Common questions
What does it mean to port a mortgage?
Porting means moving your existing mortgage deal, at its current rate and terms, to a new property when you move home, rather than repaying it and taking a new one. It is really a fresh application to your existing lender to lend against the new home on the same product. If they approve the new property and your affordability, you keep the rate you already have on the amount you carry over.
Is my mortgage automatically portable?
Not always. Portability is a feature of the specific product, so check your mortgage offer or ask your lender. Even where a deal is portable, porting is never guaranteed at the point of moving: the lender must accept the new property and reassess your income and outgoings, so a change in your circumstances can still lead to a decline.
What happens if I need to borrow more when I port?
You usually keep your ported balance on your existing rate and take the extra as a separate top-up at a current-day rate, leaving two parts on one mortgage. The overall cost is a blend of the two rates. If you need to borrow less, you may repay part of the balance, which can trigger an early repayment charge on the amount you no longer carry over, so check that first.
When is porting better than remortgaging?
Porting shines when your existing rate is much lower than today's rates and you want to keep it, or when leaving would trigger a large early repayment charge. A fresh remortgage to a new lender can win when your old rate is not special, when you need to borrow a lot more, or when another lender is simply cheaper overall. A broker compares the two on your real numbers.
Work out the combined cost with the porting calculator, and see how lenders reassess you in mortgage underwriting.
Founder, MortgageExplained, MortgageExplained
Adam spent nearly a decade as a mortgage adviser at Just Mortgages, with further experience in commercial finance. He is CeMAP and CF qualified. He built MortgageExplained to do one thing well: explain mortgages in plain English, then introduce you to a regulated broker when you are ready. Every page is written and reviewed by Adam.
Last reviewed: 21 July 2026