Fixed-rate mortgages

Should you break your fixed-rate mortgage early?

Tom Ashcombe, WatchMyMortgage · 18 November 2025 · 8 min read

It is one of the most expensive questions a homeowner can get wrong, and most of the advice online answers it with a shrug. The truthful answer is that breaking a fix early is worth it for some people and a costly mistake for others, and you can tell which one you are with a sum that takes about ten minutes. This is how the sum works.

What "breaking" your fix actually means

A fixed-rate mortgage locks your interest rate for a set period, usually two or five years. Leave that deal before it ends, whether by remortgaging to a new lender or moving to a different deal with your current one, and you normally pay an early repayment charge. That charge is the whole reason this question is hard. Without it, anyone on a high fixed rate would simply switch to a cheaper one tomorrow.

So the real question is not "is there a cheaper rate out there?". There almost always is. The question is whether the money you would save by switching is bigger than the charge you pay to leave.

The three numbers that decide it

Only three things matter, and you can find all of them on your own paperwork.

• Your early repayment charge. A percentage of the balance you clear, written in your mortgage offer. It is often around 1% to 5%, and it usually falls each year you stay in the deal.
• The gap between your rate and what you could switch to. The bigger the gap, the more you save every month by leaving.
• The time left on your fix. The saving is earned month by month, so more months left means more saving to set against the charge.

Change any one of these and the answer can move. That is why a calculation that said "not worth it" in January can say "worth it" by the summer, without you doing anything at all.

A worked example

Say you owe £200,000 at 5.5%, with 18 months left on your fix. Your early repayment charge is currently 3%, and you have been offered a new deal at 4.3% with a £999 fee.

Switching saves you roughly the difference between the two rates on your balance, about 1.2% of £200,000, which is around £200 a month. Over the 18 months left, that is about £3,600 saved.

To get it, you pay the charge of 3% on £200,000, which is £6,000, plus the £999 fee. That is £6,999 to save £3,600. On these numbers, breaking the fix today leaves you around £3,400 worse off by the time your deal would have ended. Today, you stay put.

But watch what happens to that sum over the next few months. Your charge is due to step down from 3% to 2% on a date set in your offer. The day it does, the cost of leaving drops by £2,000. If rates also drift down and the gap widens, the saving grows at the same time. There is a specific day when the £3,400 loss becomes a break-even, and then a gain. Cross that day and the honest answer flips from "stay" to "you could leave and come out ahead".

Why the date matters more than the rate

People tend to watch headline rates and ignore their own charge schedule. That is backwards. The single biggest lever in the example above was not the market. It was the day the 3% charge became a 2% charge, which knocked £2,000 off the cost of leaving overnight. That date is already written in your mortgage offer. Almost nobody has it in their diary.

Our guide to the dates that cost you money walks through every one of them: the charge step-downs, the overpayment allowance that resets each year, the six-month window when most lenders let you lock your next deal early, and the day a fix ends and the standard variable rate takes over.

The mistake that costs the most

The expensive error is not breaking too early or too late. It is waiting for your lender to tell you what to do. Lenders write to you about your fix ending, but they write on their own schedule, and the letter often arrives with little time to arrange anything better. Miss the end date and you roll onto the standard variable rate, which is commonly two to three percentage points higher. On a £200,000 balance that can be several hundred pounds a month, charged from the first day, for as long as it takes you to act.

How to work out your own answer

You do not need a spreadsheet or a broker to run the numbers. The break-my-fix calculator races staying against breaking month by month, in your browser, and marks the crossing point. For the fuller picture, put your balance, your rate, your fix end date and your charge schedule into the free timeline. It does the break-even sum properly, shows you the exact day the answer changes, and stores nothing. If you would rather see a full example first, the live demo walks through a real worked case.

One thing this is not: a recommendation. The sum tells you what each choice costs and when that cost changes. What you do with that is yours, and if you want someone to tell you the right move for your circumstances, that is a job for a mortgage adviser regulated by the Financial Conduct Authority. Take your numbers with you.

Examples are illustrative and rounded. Your own mortgage offer and lender confirm your actual figures and dates. This is information, not financial advice. For advice on your circumstances, speak to a mortgage adviser regulated by the FCA.