Moving Home With a Mortgage: Porting, Extra Borrowing and Sale Timing
Moving home with an existing mortgage? Understand porting, extra borrowing, early repayment charges and the dates to check before committing.
By PMS Mortgages · Published 14 October 2026 · Meet Ria Ali
Your home may be repossessed if you do not keep up repayments on your mortgage.
Moving home while your mortgage deal is still running raises a practical question: can you keep the rate you already have, or should you replace the mortgage? Porting a mortgage may be one option, but it needs to be considered alongside the next property, additional borrowing and the timing of your sale.
For a move from a Croydon flat to a family home in Purley, South Croydon or Coulsdon, start the mortgage discussion before treating a sale price and a new asking price as your confirmed budget. The equity, costs and lender assessment need to fit together.
What does porting a mortgage mean?
Porting normally means transferring an existing mortgage product or rate to borrowing secured on the new home with the same lender, where its terms allow it. The old loan is repaid as part of the sale and a mortgage is arranged on the new property. The property security changes; the ability to keep the product depends on approval.
Check the mortgage offer and ask the lender or adviser about the actual conditions. A portable product does not guarantee that the lender will accept a different property, a larger loan or changed household circumstances. An attractive current rate is one part of the comparison.
Start with the equity available after costs
For a planning illustration, imagine selling for £420,000 with a £260,000 mortgage balance. The gross equity would be £160,000. If you set aside an invented £20,000 for selling and purchase costs plus a reserve, £140,000 would remain towards the next purchase. On a £580,000 home, the borrowing required would be £440,000 before any fee added to the mortgage.
If porting the £260,000 balance were approved, the additional borrowing in this example would be £180,000. These are invented figures, not a valuation, cost estimate or lending offer. Ask your solicitor, estate agent and adviser for the actual costs and redemption information, and account for any early repayment charge that applies.
Keep the expected sale price separate from an agreed price and the lender’s valuation. A shortfall in sale proceeds changes the funding plan even if the desired property has not changed.
Extra borrowing can create a second mortgage part
The additional amount may have a different interest rate and initial deal end date from the ported balance. Ask to see the payment for each part and the combined total. Check how any product fees are paid and whether the remaining repayment terms differ.
Look beyond the first payment. If the ported deal ends sooner, you may have another review while the new borrowing is still within its initial period. Keep both expiry dates in a schedule and read our guide to mortgages with two parts before assuming the account can be treated as one identical loan.
What if you want to borrow less?
A smaller next purchase, a larger cash contribution or a planned lump-sum repayment can reduce the borrowing needed. Check whether an early repayment charge applies to the amount being repaid or not ported, under the lender’s terms.
Tell the adviser how much cash you want to retain after moving. Putting every pound of equity into the next property is a different instruction from reserving money for repairs or another purpose. The lender still needs to assess the proposed borrowing and property.
The sale and purchase dates need checking
If your sale and purchase complete together, explain that plan. If you expect a gap, ask how the lender handles repayment of the existing mortgage, any porting window and potential charges. Do not assume that selling first leaves the old rate available indefinitely.
For an illustrative timeline, a sale on 31 May and a purchase on 21 June create a gap that must be checked against the actual policy. The calendar example does not establish whether a lender will approve porting or refund a charge. Obtain the applicable terms before relying on a particular outcome.
Keep the solicitor and adviser informed if the dates move. A mortgage offer, sale agreement and proposed completion date need to remain consistent as the chain develops.
Compare porting with a replacement mortgage
Ask for a comparison covering the whole borrowing requirement on a consistent repayment basis. Include the rate on the ported amount, the rate on any top-up, product fees, valuation and legal costs, and any cost of leaving the existing deal. Then discuss flexibility and your plans for the next home.
For example, keeping a favourable rate on one part might still involve a different rate on a large additional balance. Equally, replacing the entire mortgage may carry a charge that changes the calculation. Neither route can be selected from one headline rate without examining the full case.
Prepare a home-move document pack
Current mortgage statement and original offer terms.
Balance, rate, repayment method and deal end date for each part.
Early repayment charge and redemption information where available.
Expected sale proceeds and a separate allowance for costs.
New property details, price and expected transaction dates.
Current income, commitments and any planned changes.
Explain whether you are selling the existing property or considering keeping it as a rental. A change of use involves a different lending discussion and should be raised before the purchase plan depends on it.
Review the move with PMS Mortgages
We can discuss the existing mortgage alongside the next purchase and investigate relevant lender requirements. Explore residential mortgage advice, our local guides for Purley and Coulsdon, or book a consultation with your mortgage statement and property plans.
General information only. Porting and additional borrowing depend on lender approval, current criteria and the property. We explain applicable advice fees before you proceed.
Sources and further reading
Frequently asked questions
No. The lender still needs to accept your application, the new property and the required borrowing. Check the offer terms and current assessment requirements.
Not necessarily. When porting and borrowing more, the additional amount may have a separate product, rate and expiry date. Review the combined payment and costs.
Yes. Timing rules and early repayment charges can apply. Check the actual lender’s conditions before selling or assuming a charge will be refunded.
Thinking about your own mortgage?
Speak to an adviser about what this means for your situation. There is no charge for an initial conversation.