Last reviewed: June 2026
TL;DR- Porting transfers the existing mortgage deal (rate and terms) to a new property when moving house, avoiding the ERC on the current deal.
- Porting is not automatic - the new property must be assessed and a new affordability check is carried out.
- If a larger loan is needed for the new property, the additional amount is taken at current market rates, not the ported rate.
- Porting is not always the cheapest option - the ported rate may be uncompetitive compared with remortgaging to the best current deal.
How Mortgage Porting Works
Porting allows a borrower to transfer their existing mortgage deal - including the interest rate and terms - from their current property to a new property when they move. The key benefit is that the early repayment charge on the current fixed or tracker deal is not triggered, because the mortgage is not being redeemed - it is being transferred to a new security (the new property).
Porting is not an automatic right. The lender must agree to the port, the new property must meet the lender's standard criteria (construction type, location, condition, minimum value), and a new affordability assessment is typically carried out. The existing mortgage terms (rate, deal period, remaining term) apply to the ported element.
What Happens When a Larger Loan Is Needed
If the new property costs more than the current property and a larger mortgage is required, the additional borrowing is taken at the lender's current rates for the additional amount - not at the ported rate. This creates a "split mortgage" with two portions at potentially different rates, expiring at different times. Managing this split - and deciding when to bring the two portions together at remortgage - adds complexity.
For example: existing mortgage £150,000 at 3.5% fixed for 2 more years. New property requires £200,000. Port the £150,000 at 3.5% and take £50,000 additional at the current 2-year rate of 5%. The two portions now have different rates but both expire in 2 years, when they can be combined at a single new rate.
When Porting May Not Be the Best Option
Porting preserves the existing rate, but if that rate is now uncompetitive relative to the current market, paying the ERC and remortgaging to the best current deal may be cheaper in total. This should be modelled: ERC cost versus the interest saving from a lower current market rate over the remaining deal period. If the existing rate is lower than current market rates (as was common for many borrowers on pre-2022 fixes), porting is clearly beneficial. If the existing rate is at or above current market rates, paying the ERC and remortgaging may cost less overall.
Chain Timing and Porting
Porting a mortgage requires the sale of the existing property and the purchase of the new property to complete simultaneously (or within a defined period set by the lender, typically 1-6 months). If the chain breaks or the timing does not work, porting may not be possible and the ERC may be triggered. Borrowers who are porting should make their estate agent and solicitor aware of the porting requirement and its timing constraints.
Frequently Asked Questions
Is porting available on all mortgages?
Most fixed rate mortgages are portable, but not all. The mortgage offer documents will state whether the product is portable. Tracker mortgages with no ERC are typically not ported because there is no ERC benefit to porting - the borrower can simply remortgage without penalty. Specialist mortgages (some buy-to-let, bridging) may not offer porting. The portability of a product should be confirmed before committing to the deal if there is any prospect of moving during the deal period.
Can I port to a cheaper property and keep the rest as cash?
If the new property costs less than the current property, the mortgage can only be ported for the amount needed on the new property. Any excess is repaid from the sale proceeds. If the ported amount is less than the existing outstanding mortgage, the difference in balance is also repaid from sale proceeds. The ERC is only avoided on the portion that is ported - a partial ERC may apply on any balance repaid early.
What if the lender declines the port because they don't like the new property?
If the lender declines the port application because the new property does not meet their criteria, the borrower must either: find a lender willing to accept the new property (which means redeeming the existing mortgage and potentially paying the ERC); or find a different property that meets the lender's criteria. The ERC applies if the mortgage is redeemed without a successful port, regardless of why the port was declined. The new property should be assessed against the lender's criteria before committing to purchase.
Can I port a buy-to-let mortgage?
Some BTL mortgages are portable; others are not. BTL porting is less common than residential porting and the criteria are often stricter. The new BTL property must meet the lender's criteria and the rental income must support the coverage requirements. A specialist BTL broker can advise on which BTL products in the market offer portability.
