Mortgage Portability: Moving Your Deal to a New Property

When you move home and you are in the middle of a fixed-rate mortgage deal, the prospect of paying an early repayment charge (ERC) to leave it early can be costly. Mortgage portability — the ability to carry your existing deal to a new property — is designed to address this. But portability is more conditional than many borrowers realise, and the top-up problem can make it less attractive than it initially appears.

What Portability Actually Means

When a lender describes their mortgage product as "portable," they are saying that — in principle — you can request to transfer the product to a new property if you sell your current home and buy another.

What portability does not mean:

• Automatic transfer without reassessment
• A guarantee that the new property will be acceptable
• The right to borrow more at your existing rate
• Freedom from any fees or checks

What portability does mean:

• You can apply to transfer your existing rate, term, and product terms to the new property
• If approved, you will not pay an early repayment charge on the amount ported
• The new mortgage is underwritten on the basis of the new property and your current circumstances

The Full Reassessment

This is where borrowers are sometimes surprised. Porting requires the lender to fully reassess your application as if it were new. They will check:

Affordability: Your income, expenditure, and the new mortgage payment against current affordability criteria. This is not your original affordability assessment from years ago — it is a new one applying current rules and stress tests. If your income has dropped, your outgoings have increased, or you have taken on new commitments, the same mortgage amount may no longer be affordable under current criteria.

Credit profile: A new credit search will be run. Any adverse events since your original application — missed payments, CCJs, defaults — will be visible. Your credit score matters as much as it did when you originally applied.

Employment: If you have changed jobs, gone self-employed, or changed employment type since your original application, the lender will reassess this. A move from permanent employment to self-employment is a significant change that could affect the outcome.

The new property: The lender will instruct a valuation of the property you are buying. Non-standard construction, short lease, structural issues, or unusual property type — all of the usual property concerns apply. If the new property does not meet the lender's standard criteria, the port will be declined even if your personal circumstances are unchanged.

This full reassessment is why porting is sometimes described as "a new mortgage application with a discount on the rate."

The Top-Up Problem

The most significant practical complication with porting arises when you are buying a more expensive property and need to borrow more than your current outstanding balance.

Example:

• Current mortgage: £200,000 outstanding at 1.9% fixed (2 years remaining)
• New property purchase price: £420,000
• Deposit available: £80,000
• New borrowing required: £340,000

You can port the £200,000 balance at 1.9%. But the additional £140,000 (the "top-up") needs to come from somewhere. The lender will offer the top-up as a new mortgage product at their current rates — which in a higher rate environment could be 4.5-5% or more.

You now have:

• £200,000 at 1.9% fixed for 2 more years
• £140,000 at 4.5% fixed for 2 or 5 years (whichever product you choose)

The rate blending problem: Your effective blended rate is higher than your ported rate but lower than the full market rate. Whether this is better than simply paying the ERC and remortgaging entirely at the current rate depends on the maths.

The end-date problem: When your ported product's fixed period ends in 2 years, you will need to deal with that portion — either remortgaging or moving to your lender's standard variable rate. The top-up's fixed period may or may not align. Managing two mortgage products ending at different times adds complexity to future planning.

When Porting Works Well

Porting is typically most advantageous when:

1. Your existing rate is significantly lower than current market rates. If you fixed at 1.5% two years ago and current rates are 4.5%, porting the maximum amount you can at 1.5% for the remaining fixed period preserves real value.

2. You are not borrowing significantly more. If your new property costs only a little more than your current one (or less), the top-up amount is small and the blended rate problem is manageable.

3. Your circumstances are unchanged. If your income, employment, and credit are stable since your original application, the reassessment should be straightforward.

4. The new property is standard. If both properties are standard construction, standard tenure, and in mainstream locations, the property assessment should not be a barrier.

When Porting Goes Wrong

Port Declined

If the lender declines the port — because your circumstances have changed, the new property is unsuitable, or affordability does not stack up — you face a decision:

• Pay the ERC and move to a new lender
• Renegotiate the purchase (if price reduction or different property could help)
• Look at whether a specialist lender could provide a new mortgage

A declined port is not the end of the road — it is the beginning of a new mortgage search. Our guide to what to do if your mortgage is declined covers the steps.

The New Property Fails the Valuation

If the lender's valuer values your new property below the purchase price, the port is effectively restricted to the lower value. This means your loan-to-value is higher than planned and you may need a larger deposit to make the numbers work. If the property has issues the surveyor flags — non-standard construction, structural concerns, short lease — the lender may decline entirely.

Simultaneous Exchange and Completion Timing

Porting typically requires your current property sale and your new property purchase to complete on the same day or within a very short window. Most lenders will not hold a ported product open for extended periods between the sale and purchase completing.

If your purchase chain falls apart after you have already completed your sale, you may find yourself without a property to port to and with the ERC clock ticking. Some lenders offer a "port bridge" — a short-term arrangement while you find a new property — but this is not universal.

Portability for Different Mortgage Types

Fixed-rate mortgages: Portability is most valuable here, because fixed-rate products carry ERCs for the full fixed term. If you are mid-fix, the ERC can be 1-5% of the outstanding balance.

Tracker mortgages: Many tracker mortgages have no ERCs, or low ones. For these, the benefit of porting is lower — you can simply move to a new tracker at a similar spread. Portability matters less.

Discount variable rate mortgages: Some have ERCs, some do not. Check the product terms.

Offset mortgages: Portability rules for offset mortgages can be complex because the offset savings account is linked to the mortgage. Whether the offset arrangement transfers to the new property depends on the lender.

What Happens to the Rate When You Port

Most lenders port the exact rate from your original product. The rate you receive on the ported portion is the same rate you have been paying — not a new rate.

This means:

• If your rate was competitive when you originally fixed, you keep that benefit
• The lender cannot apply current market rates to the ported portion
• You also keep the remaining fixed period — if 18 months remain on your 5-year fix, you continue on that basis

The one scenario where the rate can change is where the lender's product terms specify a different rate applies if the loan-to-value changes significantly. Some products have rate tiers (for example, a lower rate applies at under 60% LTV). If your LTV increases on the new property, you may drop into a higher rate tier. Read your original mortgage offer for these details.

Alternatives to Porting

If porting is not possible, not advantageous, or declined, the main alternatives are:

Paying the ERC and remortgaging: Calculate the ERC cost against the benefit of a better rate or product on the new mortgage. In some market conditions, paying the ERC and accessing a lower rate elsewhere produces a lower total cost over the remaining period.

Completing the purchase then remortgaging immediately: Some buyers complete a purchase on a different mortgage (or even an existing lender's SVR product) and immediately remortgage. This avoids the simultaneous completion complexity but adds transaction costs.

Bridging loan for the gap: Where timing of sale and purchase does not align, a bridging loan can bridge the gap — your current mortgage is repaid when your sale completes, and the bridge funds the purchase until you arrange a new long-term mortgage.

Retain the current property and let it: Consent to let from your current lender may allow you to keep your current property and rent it out while you buy the new one. This avoids having to port or pay an ERC at all — though it has tax and financial implications of its own.

The Remortgage vs Port Decision

The decision between porting and remortgaging entirely is essentially a financial calculation:

A mortgage broker can model both scenarios with actual numbers. This is not a decision to make on instinct — the numbers should drive it.

In Negative Equity

A special scenario arises when you are in negative equity — your mortgage balance exceeds the current value of your property. Porting in negative equity is theoretically possible with some lenders but practically very difficult: the new LTV on the new property would need to be within the lender's maximum, which typically requires a significant deposit, and the negative equity itself may disqualify you from porting.

Our guide to negative equity options covers the specific situation in more detail.

Practical Checklist Before Applying to Port

1. Calculate your early repayment charge — the exact amount is in your mortgage offer
2. Check what market rates are currently available from other lenders for comparable products
3. Model the blended rate if you need a top-up and assess whether the blended rate is competitive
4. Confirm your new property meets your lender's standard criteria (construction, tenure, lease length)
5. Review whether your income, employment, and credit have changed materially since original application
6. Confirm the timing of sale and purchase and how long the lender will hold the port open
7. Speak to a broker before applying — they can model both scenarios and know which lenders have port-friendly policies

This is educational content, not financial advice. Your situation is unique — speak to a qualified mortgage broker before making any decisions.