Porting Your Mortgage When You Move House: How It Works (UK Guide)

When you move house, you don't have to give up your existing mortgage deal and shop around for a new one. If your mortgage is portable, you may be able to take it, rate and term, to your new property instead. This guide covers what porting means, how lenders decide whether to allow it, what happens if your new home costs more or less, and common mistakes.

What does "porting" a mortgage mean?

Porting moves your current mortgage deal to a new property instead of paying it off and starting fresh. It's the deal that moves, not an automatic right: you redeem the old mortgage on sale, and a new loan on the same rate and terms is set up on the new property. You still have to apply, and the lender reassesses you as a new customer.

Is your mortgage portable? What to check first

Not every mortgage can be ported, and it isn't guaranteed even if your offer mentions it. Before relying on it:

• Check your mortgage offer or product terms for a portability clause.
• Contact your lender early, before viewing new properties, to find out what they'll need.
• "Portable" means the lender may allow it subject to checks at the time, not that it's automatic.

How lenders reassess you when you port

Porting is a new application: the lender reassesses income, outgoings and affordability against its CURRENT criteria, runs a fresh credit check, and values the new property.

If your income has dropped, debts have risen, credit has worsened, or lending criteria have tightened, porting can be declined even on a "portable" mortgage. How Much Can You Borrow for a Mortgage? UK Income Multiples Explained (2026) explains how lenders assess borrowing from scratch.

Moving to a cheaper home: what changes

Downsizing may mean porting only part of your balance. Lenders typically allow overpaying up to around 10% of the balance a year without a charge; beyond that, porting less than your full balance can trigger an early repayment charge (ERC) on the unported amount. Keeping your rate on a smaller loan isn't automatically better than remortgaging, so compare both.

Moving to a more expensive home: the "top-up" problem

Extra borrowing for a pricier home usually can't be added to your ported deal — it's a separate "top-up" loan. The top-up is priced at whatever rate is available then (often higher), usually carries its own arrangement fee, and leaves you managing two mortgage parts that may end on different dates. Ask your lender for the full top-up cost before committing.

Porting vs remortgaging vs a new mortgage

Lending criteria change regularly, so check your lender's current terms rather than relying on general comparisons. If porting doesn't stack up, Remortgaging UK: What It Actually Costs and When It's Worth It (2026) covers switching costs and timings.

How long does porting take?

A straightforward port commonly takes one to three months; a top-up loan or an unusual property can extend this. Since sale and purchase must complete in step, start the lender conversation once you have an offer accepted, not after exchange. What to Do After Your Offer is Accepted on a House UK (2026 Guide) covers the rest of that timeline.

Mistakes people make when porting

• Assuming porting is automatic because the mortgage is labelled "portable."
• Not comparing your ported rate with what's currently available.
• Forgetting part-porting can trigger an ERC on the amount left behind.
• Treating a top-up loan as the same terms as the original deal.
• Leaving the lender conversation too late to arrange an alternative.

The bottom line

Porting can save the cost and hassle of a new mortgage, but it's never guaranteed. Whether porting, remortgaging or a new mortgage suits you best depends on your current rate, how much more or less you need to borrow, and the market at the time. A mortgage broker or regulated adviser can run the numbers for your situation. This guide is general information, not financial advice.

Whether porting, remortgaging, buying or selling, BandBack Move keeps every step of your move organised in one free, personalised plan.