How early repayment charges (ERCs) are calculated

An early repayment charge (ERC) is what a lender may ask for if you repay some or all of a mortgage before a deal period ends. It is one of the largest swing factors in remortgage timing. A lower rate elsewhere can look attractive until the ERC and switching fees sit next to it.

Lenders do not all use the same formula. Two methods appear often in UK residential mortgage offers: a percentage of the balance (or of the amount you redeem), and a charge equal to a set number of months of interest at your current product rate. Schedules can step down over time. Overpayment allowances can carve out a free band before any charge bites. Cashback clawback can sit alongside an ERC as a separate condition.

This guide explains both common methods with two labelled EXAMPLE calculations drawn from our shared site case. The figures are illustrative only. They are not your quote. Always check the offer wording — and the Key Facts Illustration — for the method, the percentage or months, the balance the charge applies to, and the date the charge ends.

Why the method on the page matters

Remortgaging or making a large overpayment while an ERC still applies can add thousands of pounds to the true cost of leaving. Product transfers with the same lender sometimes avoid a full redemption, but that depends on the product terms — again, read the offer. Fees for valuation, legal work and product arrangement sit on top of any ERC when you switch lender.

It is usually clearer to fix the ERC figure first, then compare rates over a set horizon. Our Early repayment charge estimator turns a percentage or months-of-interest rule into a sterling estimate. Our Remortgage true cost calculator folds that estimate in with fees, cashback and rate differences. Neither tool is advice. Both exist so you can see the arithmetic before you speak to a lender or an adviser.

Independent consumer material from MoneyHelper stresses checking costs — including early repayment charges — when you compare remortgage options. The Financial Conduct Authority (FCA) publishes consumer guidance on mortgages and arranging a new deal around the end of an existing one. Those sources explain process and protections. They are not a substitute for your own lender documents.

Method 1: percentage of balance

Under a percentage method, the ERC is a stated percentage of the outstanding balance, or of the amount you repay early. Many deals use a stepped schedule — for example a higher percentage in year one of a fix, then lower percentages in later years, then zero after the deal ends. Some offers apply the percentage only to the amount redeemed above an annual overpayment allowance.

The arithmetic looks simple once you know which figure the percentage multiplies. The hard part is confirming that figure from the offer: full balance, redeemed amount, or excess above allowance. Small wording differences change the sterling result.

EXAMPLE 1: 2% of £185,000

Here is our site EXAMPLE house. Rates and percentages that are not live market prices are labelled EXAMPLE.

• Outstanding balance: £185,000
• EXAMPLE ERC method: 2% of outstanding balance on full redemption
• Months left on the current deal in the shared site case: 4

Maths: £185,000 × 2% = £185,000 × 0.02 = £3,700.

If this EXAMPLE charge still applied and you redeemed the whole loan to remortgage elsewhere, £3,700 would sit in the cost stack before product, legal and valuation fees. Over a two-year comparison horizon, that charge alone can outweigh a modest monthly saving on a slightly lower rate. Waiting until the ERC falls away is often the cleaner path — but only your offer can confirm when that date is.

Important: 2% and £3,700 are EXAMPLE figures for illustration. Your percentage, balance and schedule will differ. Always check the offer wording.

Method 2: months of interest

Under a months-of-interest method, the ERC is expressed as a number of months’ interest at the current product rate (or another rate the offer names). A common shape is “X months’ interest on the amount repaid early”. Some lenders use this instead of a percentage; some use it for part of the schedule.

A simple full-redemption illustration multiplies outstanding balance by the annual rate, divides by twelve to get one month’s interest, then multiplies by the number of months in the charge. Offers may refine that — for example using a daily rate, applying the charge only to the redeemed slice, or capping the result. Again, the offer wording controls.

EXAMPLE 2: three months’ interest at EXAMPLE 4.19% on £185,000

Same EXAMPLE balance as above. This time invent a clear months-of-interest rule for illustration only — not a claim that your lender uses these figures.

• Outstanding balance: £185,000
• EXAMPLE product rate: 4.19%
• EXAMPLE ERC rule: 3 months’ interest on the outstanding balance

Maths (simple monthly interest × months):

• One month’s interest ≈ £185,000 × (4.19 ÷ 100) ÷ 12 = £185,000 × 0.0419 ÷ 12 = £645.96 (rounded to the nearest penny)
• Three months’ interest ≈ £645.96 × 3 = £1,937.88

Equivalently: £185,000 × 4.19% × (3 ÷ 12) = £185,000 × 0.0419 × 0.25 = £1,937.88.

In this EXAMPLE, the months-of-interest charge (£1,937.88) is lower than the 2% of balance charge (£3,700) for the same £185,000 balance. That comparison is not a reason to prefer one method in the abstract. It only shows that method and inputs change the sterling result. A higher rate, more months, or a different balance would move the months-of-interest figure. A stepped percentage schedule could be higher or lower than three months’ interest depending on the year of the deal.

Important: 4.19%, three months and £1,937.88 are EXAMPLE figures for illustration. They are not live market rates and not your lender’s calculation. Always check the offer wording for the rate used, the number of months, and whether interest is calculated on the full balance or only on the amount redeemed.

What else to read in the offer

Beyond the headline method, useful lines to find include:

• the deal end date and the date any ERC schedule falls to zero
• whether partial overpayments have an annual free allowance
• whether the percentage or months apply to full redemption, partial redemption, or both
• any separate exit or admin fee on redemption
• cashback conditions and clawback periods
• portability rules if you move home during the deal

A redemption statement from your lender nearer the time remains the practical source for a live figure. Illustrations and estimators help you plan; the statement and offer settle what is owed.

Fees sit beside the ERC

When people remortgage to a new lender, the ERC is rarely the only cost. Product fees, legal fees and valuation charges can add hundreds or more than a thousand pounds. Cashback can reduce the net stack, sometimes with conditions. A product transfer may carry a smaller fee list — or none — but retention rates and features still need a fair comparison over the same horizon.

Putting ERC and fees into one true-cost view stops a headline rate from doing all the talking. That is why Remortgage Lab leads with costs before rate-hunting: fees and ERCs often decide whether a switch is worth the process.

Putting the two EXAMPLE figures side by side

• EXAMPLE percentage method: 2% of £185,000 = £3,700
• EXAMPLE months-of-interest method: 3 months at EXAMPLE 4.19% on £185,000 = £1,937.88

Same balance, different rules, different sterling outcomes. Your offer may use one of these shapes, a stepped mix, or another formulation entirely. Use the ERC estimator with the method stated in your paperwork, then feed the result into the true cost calculator alongside fees. Always check the offer wording before you treat any estimate as final.

Sources and further reading

We write in our own words. For independent consumer guidance, see MoneyHelper on remortgaging and the FCA’s consumer mortgages pages. Those pages explain process and consumer protections. They are not a substitute for reading your own lender documents.

Disclaimer

This guide and the worked EXAMPLE figures are illustrative only. They are not personalised financial advice. They are not a credit or mortgage offer. They are not an FCA-regulated recommendation. Check your lender offer (and Key Facts Illustration) for ERC method, fees and product terms. Rates and charges change. If you want advice on your situation, speak to an FCA-authorised mortgage adviser.

Next steps

Estimate your charge with the Early repayment charge estimator, then compare paths in the Remortgage true cost calculator using figures from your own paperwork. Read the ERC section of your current offer carefully. If you want regulated advice on whether to wait, transfer or remortgage, consider an FCA-authorised adviser. This site helps you organise the numbers; it does not tell you which deal to take.