Verified calculation · United Kingdom
UK early repayment charge calculator
What the charge costs, against what the overpayment removes — separated into the part that is contractual and the part that is an assumption.
Month and year only — the schedule shows months, not days.
The saving covers the charge
£5,148.91 ahead
Within the 36 months that are contractually fixed, the overpayment removes £5,598.91 of interest and costs £450.00 in charge.
What the charge comes to
| Penalty-free this year (10% of the balance) | £25,000.00 |
| Of your overpayment, free of charge | £25,000.00 |
| Above the allowance, and chargeable | £15,000.00 |
| Early repayment charge (3% of that) | £450.00 |
Contractual — no assumption
Over the 36 months left on your fix
- Interest removed
- £5,598.91
- Charge
- -£450.00
- Net
- £5,148.91
Assumes this rate never changes
Over the whole 25 years remaining
- Interest removed
- £66,028.22
- Charge
- -£450.00
- Net
- £65,578.22
How far the charge can be outrun
On these figures the interest removed stays ahead of the charge for any overpayment up to the whole balance. The charge never overtakes, so there is no crossing point to quote.
Two calculations, kept apart on purpose:
allowance = balance × allowance%
chargeable = overpayment − allowance (never below zero)
charge = chargeable × charge%
The saving is the interest the schedule no longer charges once the balance drops. Interest is worked out on the balance each month, so a smaller balance is charged less in every month that follows.
Balance, with and without the overpayment
The schedule after overpaying — 224 months
| Month | Due | Payment | Interest | Principal | Balance |
|---|---|---|---|---|---|
| 1 | Sept 2026 | £41,389.58 | £937.50 | £40,452.08 | £209,547.92 |
| 2 | Oct 2026 | £1,389.58 | £785.80 | £603.78 | £208,944.14 |
| 3 | Nov 2026 | £1,389.58 | £783.54 | £606.04 | £208,338.10 |
| 4 | Dec 2026 | £1,389.58 | £781.27 | £608.31 | £207,729.79 |
| 5 | Jan 2027 | £1,389.58 | £778.99 | £610.59 | £207,119.20 |
| 6 | Feb 2027 | £1,389.58 | £776.70 | £612.88 | £206,506.32 |
| 7 | Mar 2027 | £1,389.58 | £774.40 | £615.18 | £205,891.14 |
| 8 | Apr 2027 | £1,389.58 | £772.09 | £617.49 | £205,273.65 |
| 9 | May 2027 | £1,389.58 | £769.78 | £619.80 | £204,653.85 |
| 10 | Jun 2027 | £1,389.58 | £767.45 | £622.13 | £204,031.72 |
| 11 | Jul 2027 | £1,389.58 | £765.12 | £624.46 | £203,407.26 |
| 12 | Aug 2027 | £1,389.58 | £762.78 | £626.80 | £202,780.46 |
Figures round to the penny every month, the way a statement does, and the final payment is adjusted to clear the balance exactly.
The contractual figure covers only the months your rate is actually fixed. The whole-term figure assumes today's rate runs to the end of the mortgage, which for a fixed deal it will not — it is shown because it bounds the answer from above, not because it is a prediction.
Why this needs its own calculator
A United States fixed-rate mortgage and a United Kingdom fixed-rate deal are not the same product with a different currency symbol. A US note fixes the rate for the whole term and generally lets a borrower overpay freely. A UK deal fixes the rate for a few years, allows a stated percentage of the balance to be repaid each year without penalty, and charges a percentage of anything above that.
That is a different rule, not a different word, which is the only basis on which this site builds a country-specific tool at all. The interest arithmetic underneath is identical and is shared with the mortgage calculator — interest on a balance behaves the same everywhere. What is different is the charge, and the fact that the rate has an expiry date.
The two numbers you have to supply
This calculator asks for your overpayment allowance and your charge percentage rather than assuming them, and that is a deliberate cost. It makes the tool slower to use than one that fills in ten per cent and three per cent for you.
The reason is that neither figure is a fact about the United Kingdom. Both are contractual terms that vary by lender, by product, and often by which year of the deal you are in — a charge frequently steps down as the fixed period runs out. Any number we filled in would be wrong for most readers and, worse, uncheckable by all of them. The regulator's own framing supports reading them off your paperwork: MCOB 12.3.1R requires an early repayment charge to be"able to be expressed as a cash value" and to be"a reasonable pre-estimate of the costs" the lender incurs. It is a stated number on your offer, not an estimate you need us to guess.
A worked example you can check
Take £250,000.00 outstanding at 4.5% with 25 years left, 36 months still fixed, a 10% annual allowance and a 3% charge. The contractual monthly payment is £1,389.58.
Overpay £40,000.00. The allowance covers £25,000.00 of it, which leaves £15,000.00 chargeable. At 3% the charge is £450.00 — a figure you can confirm by multiplying, which is the whole of that step.
Against it, the overpayment removes £5,598.91 of interest within the 36 months that are actually fixed. That figure needs no assumption: the rate is contractual for those months. Net, inside the fixed period alone, the overpayment is £5,148.91 ahead.
Over the full 25 years the removed interest is £66,028.22 and the schedule shortens by 76 months — but that number assumes a rate that expires in 36 months. It is real arithmetic on an assumption that will not hold, and this page says so rather than leading with the bigger figure.
When the charge actually wins
The comparison flips, and it flips on the two things people rarely look at. Take the same balance at 1.5% with only 6 months of the deal left and a 5% charge, overpaying £50,000.00.
The charge is £1,250.00. The interest removed inside the remaining fixed months is only £313.29, so on the contractual horizon the overpayment is -£936.71 — the charge is the larger number.
On those figures the crossing point is £28,581.69: up to there the interest removed still covers the charge, and past it the charge is larger. The calculator finds that point by searching the schedule penny by penny rather than solving it algebraically, because a schedule that rounds every month does not have a clean algebraic answer.
The rule of thumb the arithmetic produces is worth stating plainly: a charge is a one-off percentage, while the saving is your rate working over the months that remain fixed. So the comparison is roughly your charge percentage against your rate multiplied by the years left on the deal. A 3% charge against 4.5% with three years to run is not a close contest. The same 3% with three months to run is a different answer entirely.
What this deliberately will not tell you
Whether to overpay. That depends on what else the money could do, on whether you would rather hold it accessible, and on circumstances no calculator can see. This page computes two quantities and shows its working; the decision is not arithmetic and is not ours to make.
It also stops at the end of your fixed period for anything it calls contractual. What happens afterwards depends on the rate you move to, and there is no honest way to compute that today.
Common questions
- What is an early repayment charge?
- A fee your lender applies when you repay more of a fixed or discounted mortgage deal than its terms allow. The FCA requires it to be "able to be expressed as a cash value" and to be "a reasonable pre-estimate of the costs" the lender incurs (MCOB 12.3.1R), which is why the figure is written on your offer rather than being something a calculator can guess.
- How much can I overpay without a charge?
- Whatever your own deal allows — commonly stated as a percentage of the balance each year. This tool takes that percentage as an input rather than assuming one, because it varies by lender, by product and sometimes by year of the deal. On the illustration here, 10% of £250,000.00 is £25,000.00, so an overpayment of £40,000.00 leaves £15,000.00 exposed to the charge.
- Is it worth paying the charge?
- That depends on two things people rarely compare: how long is left on your fixed rate, and your rate. On the illustration — 4.5% with 36 months still fixed — the £450.00 charge is outrun by £5,598.91 of interest removed inside the fixed period alone. Change it to 1.5% with 6 months left and a 5% charge, and the same comparison runs -£936.71. The tool computes both; it does not tell you what to do.
- Why do you show two different savings figures?
- Because only one of them is contractual. Your rate is fixed for a known number of months, so the interest removed inside that window rests on no assumption at all. The figure for the whole remaining term assumes today’s rate runs to the end, which for a UK deal it will not — the deal expires and the rate changes. Quoting only the larger number would be quoting a forecast as though it were arithmetic.
- Does the charge apply to the whole overpayment or just the excess?
- This tool models the common shape: the allowance is free, and the charge applies to the amount above it. Some lenders word it differently, and a few apply the charge to the whole repayment once the allowance is breached. Read your own terms — and if yours works the other way, put the whole overpayment in as the chargeable amount rather than trusting this model.
- What is not included here?
- Exit or deeds-release fees, any product fee added to the loan, the rate you will move to when the deal ends, and whether the money would do more elsewhere. The first two are cash amounts you can add yourself; the third is unknowable today; the fourth is not an arithmetic question.
Sources
- FCA Handbook — MCOB 12.3 Early repayment charges: regulated mortgage contracts — retrieved 2026-08-18
- Every figure in the worked examples is produced at build time by the same engine the calculator above runs. No interest rate, allowance or charge on this page is quoted from any lender — the scenarios are illustrative shapes, and the two figures that matter are the ones you read off your own offer.
Written and maintained by Vikash Singh. Last verified 2026-08-18.