Guide · 9 min read

When does remortgaging make financial sense.

Updated May 2026

Switching to a better mortgage rate saves money every month. But exiting your current deal early usually costs money upfront. The break-even calculation tells you whether switching now, waiting, or staying put makes the most financial sense.

The cost of switching early

When you take out a fixed-rate mortgage, the lender sets the rate based on their cost of funds for that period. If you leave before the fixed term ends, the lender recovers some of that cost through an Early Repayment Charge (ERC). The ERC is typically expressed as a percentage of the outstanding mortgage balance.

Standard ERC structures in the UK look like this: a 5-year fix might charge 5% in year one, 4% in year two, 3% in year three, 2% in year four, and 1% in year five. A 2-year fix typically charges 2% in year one and 1% in year two. The percentages and taper structures vary by lender and product, so always check your specific mortgage illustration or contact your lender directly.

On a £300,000 outstanding balance with a 2% ERC: the charge is £6,000. That is real money you pay immediately in exchange for a potentially lower rate going forward. The question is whether the future savings exceed that cost — and how long it takes to reach that point.

The other costs of switching

The ERC is usually the largest cost, but it's not the only one. A complete list of costs to factor in:

• Arrangement or product fee — most competitive fixed-rate deals carry a fee of £999 to £1,999 to access the best rates. Some products are "fee-free" but carry a slightly higher rate; whether the fee-free option is better depends on your balance and how long you hold the deal.
• Valuation fee — some lenders require a valuation of the property. Many offer free valuations for remortgage applications, but it's worth checking.
• Legal fees — straightforward remortgages (staying on the same property, no additional borrowing) are typically handled by the new lender's panel solicitor at no cost to you. If you're also borrowing more or changing the ownership structure, legal fees can apply.
• Broker fee — if you use a mortgage broker, they may charge a fee of £300 to £700, though many fee-free brokers earn commission from lenders instead.

Add all the applicable costs together to get your total switching cost. This is the number you compare against your monthly saving.

The break-even calculation

Once you have the total switching cost and the monthly saving, the break-even point is straightforward:

If the break-even point is before your new fixed term ends, switching makes financial sense. If it extends beyond the new term — or beyond the point when you are likely to move or remortgage again — then staying put may be the better decision.

Worked example

Scenario: you have a £300,000 mortgage balance with 18 months remaining on your current 5-year fix. Your current rate is 5.2%. A new 2-year fix is available at 4.2%, saving 1 percentage point. Your outstanding balance means the monthly saving would be approximately £150 per month.

Costs of switching:

• ERC: 2% of £300,000 = £6,000
• Arrangement fee on new deal: £999
• Valuation: free (lender covers it)
• Legal fees: free (lender covers for straightforward remortgage)
• Total switching cost: £6,999

Break-even calculation:

• Monthly saving: £150
• Break-even: £6,999 ÷ £150 = 47 months

The new deal is a 2-year (24-month) fix. The break-even point of 47 months falls after the new deal ends, meaning you would never recover the switching cost before your next remortgage. In this scenario, it is cheaper to stay on the current deal for the remaining 18 months and then switch at no ERC cost.

Now adjust the scenario: only 6 months remaining on the current fix, same 1-percentage-point saving, same arrangement fee. ERC drops to 1% = £3,000. Total switching cost: £3,999. Break-even: £3,999 ÷ £150 = 27 months — which falls within the new 2-year deal. In this version, switching now makes financial sense.

When ERC timing changes everything

The ERC taper means that the financial case for switching improves dramatically as you approach the end of your fixed term. In the example above, the difference between 18 months remaining (don't switch) and 6 months remaining (do switch) comes from the ERC dropping by £3,000. The month-by-month ERC reduction is worth calculating, especially if rates are volatile. Sometimes waiting just two or three months — to fall into the next ERC percentage tier — transforms the maths completely.

The product fee dilemma

Many borrowers automatically choose fee-free products to avoid upfront cost. But for larger mortgages, a product with a £999 arrangement fee can be significantly cheaper overall if the rate is lower. Consider two deals on a £300,000 mortgage:

• Deal A: 4.10% with a £999 fee. Monthly payment ≈ £1,577.
• Deal B: 4.30% fee-free. Monthly payment ≈ £1,609.

Deal A saves £32 per month. Over a 2-year fix, that is £768 in payment savings against the £999 fee — Deal B is slightly cheaper over 2 years. Over a 5-year fix, the £32-per-month saving generates £1,920 against the £999 fee — Deal A comes out significantly ahead. The length of the fix determines which product structure wins.

Remortgaging vs product transfer

When your fixed term ends, you do not have to remortgage to a new lender — you can also accept a new deal from your existing lender, known as a product transfer. Product transfers are faster, cheaper (usually no legal fees or valuation), and involve no new affordability assessment. This makes them attractive if your circumstances have changed (new self-employment, reduced income) or if you want a quick, low-friction process.

The trade-off is that product transfers give you only one lender's rates versus the whole market. A broker can compare your existing lender's product transfer offer against the full market in minutes, which is almost always worth doing before you accept. The difference between the best product transfer rate and the best market rate is often 0.1–0.3 percentage points — which on a £300,000 mortgage is £300–£900 per year.

What the calculator shows

The remortgage break-even calculator on this site takes your outstanding balance, current rate, ERC percentage, arrangement fee on the new deal, and the new rate. It calculates the total switching cost, the monthly saving, and the break-even point in months — letting you see immediately whether switching now makes financial sense for your specific situation. Try adjusting the ERC percentage to model what the maths look like if you wait for the next taper date.

Try the calculator: Remortgage break-even calculator →