Building Society Mortgage Porting Guide: Moving Home

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UK Mortgage Guide • Moving Home

Building Society Mortgage Porting: How to Move Home Without Losing Your Deal

If you have a mortgage with a UK building society and want to move house, you may be able to keep your existing fixed or tracker deal. This is called mortgage porting.

Porting can save you from giving up a competitive interest rate or paying an Early Repayment Charge (ERC). But approval is not automatic. Your building society must assess your new property, borrowing needs and current circumstances before agreeing to the move.

How to Port Your Mortgage Check Building Society Rules Check Costs & ERCs
Important: A portable mortgage does not guarantee that you can move the deal. The lender can still decline a new mortgage application because of affordability, credit, loan-to-value or property concerns. Do not exchange contracts relying on a port that has not been approved.

Independent UK mortgage information • Reviewed 14 October 2026 • No personalised mortgage advice or guaranteed lending decisions.

Mortgage Porting: Quick Answers

What is porting?Keeping an eligible mortgage interest-rate deal or product when moving to a different property with the same lender.
Do you reapply?Yes. The new loan and property normally require a fresh assessment and mortgage application.
Same interest rate?The ported portion generally keeps the original product rate until its existing deal ends.
Borrowing more?Additional borrowing normally uses a separate current mortgage product and rate.
Can you avoid an ERC?Often, subject to the lender’s porting conditions and completion arrangements.
Moving to a cheaper home?Possible, but reducing your mortgage balance can trigger a charge on the amount not ported.
Sale and purchase on different dates?Some societies permit a gap and offer ERC refunds if you complete within their deadline.
Best first stepCheck the portability clause in your mortgage offer and speak to your existing lender before committing to a purchase.
Quick answer: You normally port the mortgage product, not the original mortgage loan itself. The old mortgage is repaid when you sell, and a new mortgage is secured against the home you buy, with your existing deal terms carried over where approved.

What Does Porting a Mortgage Actually Mean?

Suppose you took out a five-year fixed mortgage two years ago. You now want a larger house, but the fixed rate has another three years to run.

Instead of automatically paying off that deal and choosing a new product, your building society may allow you to carry the remaining three years of the fixed-rate product onto the mortgage secured against your new home.

Example: Keeping Your Existing Fixed Rate

£180,000Existing mortgage balance
2.79%Existing fixed interest rate
3 yearsFixed deal remaining
£180,000Amount proposed for porting

If approved, the £180,000 ported portion could continue at 2.79% for the remaining three years. Any extra borrowing would usually be priced separately under a product available when you apply.

Illustrative figures only, not a current building society mortgage quote. The new loan’s repayment term and other arrangements remain subject to approval.

Porting versus a product transfer: Porting is connected to moving to another property. A product transfer normally means changing the mortgage deal on the property you already own, often when an introductory rate is ending. The two processes are not interchangeable.

Can You Port Your Existing Building Society Mortgage?

Start with your most recent mortgage offer and product conditions. Look for wording such as “portable”, “moving home”, “portability” or “transfer to another property”.

Even if the original product is portable, approval usually depends on the following.

AffordabilityYour current income, household expenses, debts and financial commitments must meet the lender’s assessment.
Credit historyMissed payments, new credit commitments or changes since the original application can affect approval.
Loan-to-value (LTV)The new borrowing must fall within the applicable maximum LTV for your product and property.
Property suitabilityThe building society must accept the property as mortgage security following valuation and underwriting.
Borrower changesAdding or removing a borrower may require additional checks and can affect eligibility.
Existing product termsSome older, specialist, shared ownership, buy-to-let or other mortgage products have additional restrictions.
A common misconception: Your lender previously approving a £250,000 mortgage does not mean it must approve the same amount today. Employment, dependants, credit commitments and lending rules may have changed.

How to Port a Building Society Mortgage When Moving Home

Start the conversation as soon as you are seriously considering moving. Do not leave porting enquiries until your conveyancer is preparing completion statements.

  1. Find your mortgage offer. Check whether the product is portable, when your deal ends and the ERC that applies if you repay early.
  2. Contact your building society. Tell the mortgage team that you plan to move home and want to retain your existing product if eligible.
  3. Explain the new borrowing requirement. Give a realistic estimate of the sale price, outstanding balance, expected deposit, purchase price and additional borrowing.
  4. Complete the affordability or Decision in Principle stage. Your lender may ask for updated income, outgoings and credit information before proceeding.
  5. Apply for the new mortgage. Once the property and borrowing details are known, complete the full porting or moving-home application.
  6. Arrange valuation and legal work. The lender must accept the property, and your conveyancer must manage the sale, redemption and new mortgage security.
  7. Review the formal mortgage offer. Check which amount is ported, its rate, any separate additional-borrowing rate, fees, ERC treatment and completion conditions.
  8. Coordinate completion. Your conveyancer and lender arrange repayment of the existing loan and release of funds for the new property.
  9. Check the new account after moving. Confirm both mortgage sub-accounts, payment amounts, Direct Debit details, deal end dates and any ERC refund due.
Practical tip: Tell your conveyancer and mortgage adviser that the transaction involves porting. They need to understand any lender-specific redemption deadline, completion gap and ERC refund conditions.

Documents and Information to Prepare

The building society may already hold information from your previous mortgage application, but can still request updated documents for the new lending decision.

Existing mortgage account number
Original or latest mortgage offer
Outstanding mortgage balance
Current fixed or tracker deal end date
Expected sale price and equity
New property address and purchase price
Recent payslips or self-employed income evidence
Recent bank statements if requested
Details of loans, credit cards and commitments
Deposit and source-of-funds information
Photo identification where requested
Conveyancer’s details

The exact evidence varies by lender, income type and application. Upload personal documents only using your building society’s approved secure process.

Porting a Mortgage and Borrowing More for a Bigger Home

Upsizing is where porting can become more complicated. You might want to keep your existing rate while borrowing extra money to cover a more expensive house.

Example: Existing Deal Plus Additional Borrowing

£160,000Ported mortgage balance
£60,000Additional borrowing
£220,000Total new mortgage

Suppose the existing £160,000 has a 2.50% fixed rate and the additional £60,000 is offered at 4.75%.

You would effectively have two mortgage portions under the new overall borrowing arrangement:

  • £160,000 continuing on the ported rate, subject to the lender’s conditions.
  • £60,000 on the new product and rate.

The two portions may have different end dates, fees, overpayment allowances and ERCs.

Illustrative rates only. They do not represent a live lending offer.

Why Two Mortgage Sub-Accounts Matter

Having different fixed-rate expiry dates can make future decisions more awkward. For example, one portion might expire in 2028 and the other in 2031.

Ask whether you can later align the deals, what it would cost and whether making an overpayment will reduce one portion or be distributed between them.

Can You Port a Mortgage When Downsizing?

Yes, potentially. The problem is usually not the smaller property itself, but the amount of borrowing you still need and the part of the original mortgage you are repaying.

Example: Porting Only Part of Your Mortgage

£190,000Existing mortgage balance
£130,000Mortgage needed on new home
£60,000Balance not being ported

You might be able to carry £130,000 of the existing deal to the new property, but the lender may apply an ERC to some or all of the £60,000 being repaid early.

Whether a charge applies depends on the product, permitted overpayments, porting conditions and any partial-redemption rules.

Do not assume porting removes every ERC. Ask for the charge on the exact amount you intend to redeem, not only the ERC payable on the full existing mortgage.

Mortgage Porting Costs and Early Repayment Charges

Porting does not mean moving house without mortgage-related fees. You are still buying a property, arranging security for the new loan and potentially changing borrowing amounts.

Cost
When it may apply
What to check
Early Repayment Charge
The existing mortgage is repaid during an ERC period.
Whether porting waives, reduces or refunds the charge, and the conditions.
Valuation
The building society must assess the new property.
Whether there is a fee and whether it is refundable.
Mortgage product fee
You take additional borrowing on a fee-charging product.
Total cost after the fee, not just the headline rate.
Legal and conveyancing
The sale and purchase require legal work.
Fees, disbursements, leasehold work and any lender-specific requirements.
Property taxes
A home purchase triggers applicable transaction taxes.
SDLT in England and Northern Ireland, LBTT in Scotland or LTT in Wales, as applicable.
Other moving costs
Survey, removals, estate agency and associated work.
Budget for these separately from the mortgage offer.

How an ERC Could Affect Your Decision

Suppose your mortgage balance is £200,000 and the contractual ERC is 3% of the amount being repaid.

£200,000Illustrative repayment balance
3%Illustrative ERC rate
£6,000Illustrative ERC

Porting could help avoid or recover this charge if the lender’s conditions are met. However, a new mortgage elsewhere could still be financially preferable once interest and fees are compared over the relevant period.

This is an illustration, not an estimate of your personal ERC. Request the actual redemption statement and porting conditions from your lender.

Independent UK guidanceMoneyHelper: Costs of Buying, Selling and Moving Home

After opening this link:

  1. Review the main buying and selling cost categories.
  2. Identify costs that apply to your UK nation and property transaction.
  3. Add expected mortgage fees, legal charges and any ERC separately.
  4. Set aside a contingency rather than using every pound of available equity as your deposit.

What Happens if Your Sale and Purchase Complete on Different Dates?

One of the most important porting details is whether the sale of your existing home and purchase of the next property must complete together.

Some building societies allow a gap between redeeming the old mortgage and completing the new mortgage. Others impose different requirements.

Same-day completionThe existing mortgage is redeemed and the new mortgage completes as part of the linked transactions. This can make ERC handling simpler, depending on the lender.
Completion gapYou sell first and buy later. The lender may initially collect the ERC and refund it after qualifying completion.
Deadline missedIf the new purchase completes after the permitted porting period, you may lose entitlement to any expected ERC refund.
Change of propertyIf the agreed purchase falls through, the lender may need to reassess a replacement property and adjust its approval.
Examples from official lenders: Coventry Building Society and Yorkshire Building Society currently describe porting arrangements involving a maximum gap of six months in qualifying situations. This is not a universal UK mortgage-porting rule.

Before fixing your completion date, obtain written confirmation of the lender’s deadline, which events start the clock, how a refund is claimed and whether your new mortgage must be for a minimum qualifying amount.

Building Society Mortgage Porting Rules: Where to Check

Different UK building societies use different conditions. Use your existing lender’s policy and mortgage offer as the controlling documents, not another society’s rules.

NationwideNationwide Building Society: Porting Your Mortgage

Nationwide confirms that porting means taking an existing mortgage deal to a new property through a new application. Its moving-home process begins with a Decision in Principle, followed by the lending assessment and mortgage application.

After opening this link:

  1. Read the explanation of transferring the product rather than the original loan.
  2. Check your current mortgage offer for portability and ERC conditions.
  3. Review whether changed income, new borrowing or LTV affects eligibility.
  4. Follow Nationwide’s Decision in Principle route and discuss the port with a mortgage adviser.

Yorkshire Building SocietyYorkshire Building Society: Moving With Your Mortgage

YBS explains the possibility of keeping an existing rate when moving home. Its published guidance also describes ERC avoidance or refunds in qualifying cases where the sale and new purchase meet its timing rules.

After opening this link:

  1. Read the moving-home eligibility requirements.
  2. Check whether the whole mortgage balance or only part will be ported.
  3. Review the six-month condition relating to qualifying ERC refunds.
  4. Contact YBS for the assessment of your property and borrowing requirements before making commitments.

Coventry Building SocietyCoventry Building Society: Moving Your Mortgage

Coventry says most of its mortgages are portable, subject to terms and a fresh application. Its current guidance sets a maximum six-month gap between redemption and completion for the relevant porting arrangement and explains that additional borrowing is held in a separate sub-account.

After opening this link:

  1. Check the portability wording for your existing mortgage.
  2. Read the separate conditions for porting all or part of the balance.
  3. Review the rules for additional lending and LTV.
  4. Check the six-month redemption-to-completion requirement.
  5. Call Coventry’s published mortgage help number, 0800 121 8899, to discuss the application.
Do not copy another lender’s deadline. Even where two building societies both mention six months, their ERC calculation, qualifying repayment amounts, refund rules and documentation may differ.

Is It Better to Port Your Mortgage or Take a New Deal?

The choice depends on both the rate you would preserve and the full cost of the alternative.

Consideration
Port existing deal
Take a new deal
Interest rate
Preserves an eligible existing product rate on the ported balance.
Uses the new product rate available at application.
ERC
May be waived or refunded under qualifying rules.
May need to be paid if leaving the original deal early.
Borrowing more
Often involves a separate new product.
May allow one product to cover the total new borrowing.
Deal expiry
Original deal expiry normally stays in place.
A fresh introductory period starts under the new agreement.
Affordability
Fresh assessment typically required.
Fresh assessment required.
Property checks
New property must meet the lender’s requirements.
New property must meet the new lender’s requirements.

Compare Total Cost, Not Just the Headline Rate

Ask your adviser to compare the remaining fixed period first. Include interest, product fees, ERCs and any charges directly attributable to the choice.

If one option results in a longer mortgage term, compare that separately. Lower monthly repayments over a longer term can increase the overall interest paid.

Porting may be attractive when: your existing rate is significantly below the available market rates, you still have a substantial ERC period and the building society can approve the new borrowing on acceptable terms.
A new deal may be worth considering when: your current product is near expiry, no substantial ERC applies, the new mortgage is much larger or the lender’s current deals are more suitable overall.

What Can Go Wrong With Mortgage Porting?

The following situations are worth checking early, especially if you have already found a property or accepted an offer on your current home.

Your income has fallenYou may no longer meet affordability criteria. Ask the lender what options exist and whether revised borrowing could help.
The new property is rejectedSome construction types, property conditions, leases or valuation concerns can fall outside a lender’s accepted security criteria.
The new home costs moreThe lender may approve the ported amount but decline the additional borrowing needed to buy the property.
The purchase is delayedA completion gap can affect the porting deadline and any expected ERC refund.
The mortgage has multiple sub-accountsDifferent balances may have different product terms, expiry dates and portability conditions.
Borrowers are changingSeparation, divorce or removing a joint borrower can require affordability and legal reassessment.

If the Building Society Refuses the Port

  1. Ask for the reason for refusal and whether it relates to affordability, credit, the property, LTV or the product conditions.
  2. Check whether correcting an error or adjusting the proposed loan could change the outcome.
  3. Consider independent regulated mortgage advice about alternative lenders and the total cost of leaving your existing deal.
  4. Request an accurate ERC and redemption statement before making a new commitment.
  5. If you believe the lender applied its published terms incorrectly, follow its complaints procedure and retain written evidence.
Important: A complaint does not automatically extend a mortgage offer, a conveyancing deadline or an ERC refund period. Keep the practical moving arrangements under review separately.

Special Cases: Joint Mortgages, Buy-to-Let and Moving Before Your Deal Ends

Joint borrowers separating

Porting into one person’s name may require the remaining borrower to pass affordability checks alone. Ownership transfer and legal arrangements need separate attention.

Buy-to-let mortgages

Do not assume residential porting rules apply to buy-to-let products. Eligibility may depend on rental income, landlord criteria and the new property’s suitability.

Moving close to deal expiry

Compare whether retaining a rate for only a few remaining months is worthwhile after fees and lender requirements.

Buying before selling

Owning both properties temporarily can create affordability, funding and transaction-tax issues. Standard porting may not fund both mortgages simultaneously.

Questions to Ask Your Building Society Before Making an Offer

Use this checklist during a mortgage adviser appointment. Ask for important answers in writing.

Is every part of my current mortgage portable?
What is the maximum amount I can port?
Would I need a new affordability assessment?
What LTV limit applies to the new property?
Can I borrow more, and at what type of rate?
Will the additional borrowing be a separate sub-account?
What ERC applies if I port less than the full balance?
Will an ERC be refunded if completion dates differ?
What exact deadline applies to the purchase?
What fees and valuation requirements apply?
Will my existing product expiry date stay the same?
What happens if the new purchase falls through?

More Official Guidance Before You Decide

MoneyHelperMoneyHelper: Remortgaging and Porting Considerations

MoneyHelper explains that portable mortgages still involve new affordability checks and that additional borrowing may be offered on a separate deal.

After opening this link:

  1. Find the guidance about moving home with an existing mortgage.
  2. Review why a portable deal may still require a fresh approval.
  3. Compare the cost of remaining with your lender against taking a new deal.
  4. Consider speaking with a regulated mortgage adviser if the alternatives are difficult to assess.

FCA registerFinancial Conduct Authority Firm Checker and Register

Use the regulator’s register to verify firms or advisers involved in arranging a mortgage.

After opening this link:

  1. Search the mortgage adviser or firm’s official trading name.
  2. Check its authorisation and relevant permissions.
  3. Compare the recorded contact information with the details given to you.
  4. Be cautious if someone pressures you to pay into an unfamiliar account or refuses to provide verifiable firm details.

Related Building-Society.org Mortgage Guides

These published guides provide lender-specific context if you are comparing moving-home options or considering a new deal.

Nationwide Mortgage Rates, Remortgages and Existing-Customer Deals Coventry Building Society Mortgage Rates and Product Options Yorkshire Building Society Mortgage Rates and Remortgage Guide Market Harborough Building Society: Existing Mortgage and Porting Help Nationwide Building Society: Accounts, Mortgages and Customer Services

Official Sources and Editorial Checks

This guide uses published UK building society and MoneyHelper information to explain the process. Your individual mortgage offer, product conditions and lender’s latest written decision take priority.

Nationwide: Porting Your Mortgage Nationwide: Moving Home Mortgages Yorkshire Building Society: Moving With Your Mortgage Coventry: Moving Your Mortgage MoneyHelper: Remortgaging MoneyHelper: Buying and Moving Costs
Editorial approach: Lender-specific porting eligibility, completion gaps and ERC conditions have been distinguished from general mortgage guidance. Example rates and balances are illustrative rather than live offers. Current mortgage pricing should be obtained directly from the lender.

Mortgage Risk and Independent Website Notice

Building-society.org is an independent information website. It is not a mortgage lender, broker or representative of the building societies discussed on this page.

This guide is general information, not a personal mortgage recommendation. Approval depends on the lender’s underwriting, affordability assessment, valuation and product criteria.

Your home may be repossessed if you do not keep up repayments on your mortgage. Before exchanging contracts, obtain the formal mortgage offer and check with your conveyancer and mortgage adviser that the transaction and financing arrangements are workable.

Building Society Mortgage Porting FAQs

1. What is building society mortgage porting?

Mortgage porting is the process of moving an eligible existing mortgage product or interest-rate deal to a new property with the same lender. The original mortgage is normally repaid, and a new mortgage is arranged on the new home, subject to approval.

2. Can I keep my fixed mortgage rate when moving house?

You may be able to keep your existing fixed rate on the amount approved for porting until the original deal ends. The lender must approve the new mortgage and property. Any additional borrowing usually uses a separate product and rate.

3. Do I need a new mortgage application to port?

Yes, normally. Porting generally requires a new mortgage application, affordability assessment, property valuation and underwriting decision. Having an existing mortgage with the building society does not guarantee approval.

4. Can I borrow more money when porting my mortgage?

Potentially. If you meet the lender’s affordability and LTV rules, you may be offered additional borrowing on a separate current mortgage product. The extra borrowing may have a different rate, fee and deal expiry date.

5. Do I pay an Early Repayment Charge when porting?

Not necessarily. Some building societies waive an ERC or refund it when a qualifying port completes under their rules. An ERC may still apply to an amount not ported or where the completion deadline or other conditions are missed.

6. How long do I have between selling and buying when porting?

There is no single deadline applying to every building society. Coventry Building Society and Yorkshire Building Society currently describe six-month periods for qualifying porting arrangements, but your own lender’s exact conditions must be checked.

7. Can I port my mortgage to a cheaper house?

Yes, subject to approval, but you might need a smaller mortgage. If part of your existing balance is repaid rather than ported, the lender may charge an ERC on that part under the product conditions.

8. Can a building society refuse to port my mortgage?

Yes. Even if your product is portable, the lender can decline a new application because of affordability, credit history, loan-to-value, property suitability or other lending criteria.

9. Is porting better than remortgaging?

It depends on the rate you can preserve, the Early Repayment Charge, additional borrowing needs, mortgage fees and the cost of alternative deals. Compare total costs over a suitable period rather than choosing solely by the headline interest rate.

10. Should I speak to my building society before making an offer?

Yes. Check portability, affordability, borrowing limits, ERC treatment and the application process as early as possible. Do not exchange contracts assuming the port has been approved until you have a formal mortgage offer and your conveyancer confirms the arrangements.

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