Remortgage or Overpay? What to Do When Your Fixed Rate Ends
The end of a fixed-rate deal is the one point in your mortgage when the early repayment charge disappears. You can pay down as much as you like, shorten the term, or leave your cash invested and simply lock in a new rate. Here is what each option is worth in pounds, and how to choose the right one for a UK FIRE plan.
Published: 28 September 2026 at 09:00 · 7 min read
The Short Answer
Always secure a new deal, then decide how much spare cash to put in on the switch date. Doing nothing puts you on the standard variable rate, which can cost around £500 a month more on a typical balance. Once the new rate is lined up, the end of the fix is the best moment to overpay, because a lump sum of any size goes in without an early repayment charge.
Take a common 2026 example: £250,000 borrowed in 2021 at 1.8% over 30 years, paying £899 a month. After five years the balance is about £217,100. Remortgaged at 4.5% over the remaining 25 years, the payment jumps to £1,207. A £20,000 lump sum at the switch, with the payment kept at £1,207, saves around £36,400 of interest and clears the mortgage 3 years 10 months early. Whether that beats investing the £20,000 depends on your emergency fund, your tax position and how close you are to FIRE.
What Are Your Options When a Fix Ends?
There are four main moves, and you can combine them:
- Product transfer: a new deal with your existing lender. Usually quick, with no new valuation, legal work or affordability check if you are not borrowing more or extending the term.
- Remortgage: move to a new lender for a better rate. Full application, affordability check and valuation, though free legals and valuations are common.
- Lump-sum overpayment: reduce the balance before the new deal starts, cutting either the payment or the term.
- Shorter term: lock in a higher contractual payment so the mortgage ends sooner.
The option to avoid is doing nothing. On our example, an SVR of 7.25% would mean a payment of about £1,569 and roughly £500 a month more interest than a 4.5% fix. Lenders signed up to the Mortgage Charter let existing customers lock in a new deal up to six months before the fix ends, and most will let you switch to a cheaper product if rates fall before it starts.
How Much Does a Lump Sum at Renewal Save?
Using the same £217,100 balance, remortgaged at 4.5% over 25 years (£1,207 a month, about £144,900 of total interest):
| Lump sum at switch | Keep payment at £1,207: interest saved | Mortgage-free earlier by | Reduce payment instead | Interest saved (reduced payment) |
|---|---|---|---|---|
| £10,000 | £19,400 | 2 years | £1,151 (−£56) | £6,700 |
| £20,000 | £36,400 | 3 years 10 months | £1,096 (−£111) | £13,400 |
| £30,000 | £51,200 | 5 years 7 months | £1,040 (−£167) | £20,000 |
Two things make the switch date special. First, on the new deal you would normally be limited to overpaying 10% of the balance a year (about £21,700 here) without a charge; between deals there is no cap. Second, a lump sum can drop you into a lower loan-to-value band, which gets you a cheaper rate on everything that is left.
The loan-to-value bonus
Lenders price deals in LTV bands, typically 60%, 75%, 85% and 90%. If the house in our example is worth £350,000, a £217,100 balance is 62% LTV. An overpayment of just £7,100 brings it to £210,000, exactly 60%. If that unlocks a rate of 4.3% instead of 4.5%, the payment drops to £1,144 and interest over a five-year fix falls from about £46,000 to £42,500. That is a saving of around £3,500 in five years from £7,100, roughly a 10% annual return, which is hard to beat anywhere. Ask your lender or broker where the band edges are before you decide how much to put in.
Should You Shorten the Term Instead?
Remortgaging is also your chance to reset the term. Cutting it forces the higher payment into the contract:
| New term (£217,100 at 4.5%) | Monthly payment | Total interest | Saved vs 25 years |
|---|---|---|---|
| 25 years | £1,207 | £144,900 | — |
| 22 years | £1,297 | £125,300 | £19,600 |
| 20 years | £1,374 | £112,500 | £32,400 |
| 18 years | £1,468 | £100,100 | £44,900 |
| 15 years | £1,661 | £81,800 | £63,100 |
A shorter term and regular overpayments give almost identical results if you actually make the overpayments. The difference is flexibility. Staying on 25 years and voluntarily paying £1,374 means you can drop back to £1,207 during a career break, a Barista FIRE phase or a job loss. Signing up to 20 years removes that safety valve, but it also removes the temptation to stop. Just watch the 10% cap: overpaying £167 a month is about £2,000 a year, well within it.
A shorter term also means the lender will test affordability on the higher payment. Use our mortgage affordability calculator to check you have headroom before asking. For our full comparison, see reduce the term or the payment.
Overpay or Keep the Cash Invested?
Overpaying at 4.5% is a guaranteed, tax-free 4.5% return. Investing is not guaranteed, but over 25 years the gap can be large. Here is what £30,000 could be worth, with the overpayment expressed as its equivalent compounded value:
| £30,000 over 25 years | Annual return | Value after 25 years |
|---|---|---|
| Mortgage overpayment (guaranteed) | 4.5% | £90,200 |
| Stocks & Shares ISA, poor decades | 3% | £62,800 |
| Stocks & Shares ISA, moderate | 6% | £128,800 |
| Stocks & Shares ISA, historical long-run average | 7% | £162,800 |
Pension contributions tilt things further towards investing: a higher-rate taxpayer gets 40% tax relief, so £18,000 from take-home pay becomes £30,000 in a SIPP on day one. A sensible order for most UK FIRE pursuers:
- Keep a full emergency fund outside the house.
- Clear any debt costing more than the mortgage, such as credit cards or car finance.
- Take any employer pension match and use salary sacrifice where available.
- Use spare cash to cross an LTV band edge if one is close, because that return is exceptional.
- Then split between overpaying and your ISA based on how much certainty you want.
Your FIRE timeline matters too. If you plan to stop work within five to ten years, clearing the mortgage first can cut your FIRE number substantially, since every £1,000 a year of spending needs about £25,000 invested at a 4% withdrawal rate. It also avoids a problem unique to early retirees: once you have left work, a new lender may not offer you a remortgage at all, because affordability is based on income. A product transfer with your existing lender usually avoids that, but you lose the chance to shop around. Read more in retiring with a mortgage and pay off the mortgage or invest.
What about fees and deal length?
On a five-year fix, a 0.1 percentage point rate difference is worth roughly £1,000 per £200,000 borrowed. So a £999 product fee pays for itself on a £200,000 loan if it cuts the rate by at least 0.1%, but on a £100,000 loan you need a 0.2% cut. If you plan to overpay heavily, consider a tracker or a deal with unlimited overpayments: the rate may be slightly higher, but you avoid ERCs entirely. Our offset vs overpaying guide covers the other flexible option.
Frequently Asked Questions
Should I overpay my mortgage when my fixed rate ends?
The end of a fix is the one moment you can usually overpay any amount without an early repayment charge, so if you have cash you do not need, it is the best time to do it. On a £217,000 balance remortgaged at 4.5% over 25 years, a £20,000 lump sum at the switch saves about £36,400 of interest if you keep the payment the same, clearing the loan 3 years 10 months early. Keep your emergency fund first, and compare the guaranteed 4.5% against what the money could earn invested in an ISA or pension.
Can I overpay without a penalty when my fixed rate ends?
Yes, in most cases. Once your fixed deal expires and before a new one starts, you are on the lender's standard variable rate, which normally has no early repayment charge, so you can overpay as much as you like. Many lenders also let you make a lump-sum payment on the day a product transfer takes effect. Check with your lender first, because the new deal's ERC and 10% overpayment limit start from the day it begins.
Is it better to shorten my mortgage term or overpay when remortgaging?
Shortening the term commits you to a higher payment; overpaying gives the same saving but keeps the lower contractual payment as a fallback. On £217,000 at 4.5%, cutting the term from 25 to 20 years raises the payment from £1,207 to £1,374 and saves about £32,400 of interest. Paying £1,374 on a 25-year deal achieves almost the same result if you stick to it. A shorter term also means an affordability check on the higher payment, which can be harder if you have already left full-time work.
What happens if I do nothing when my fixed rate ends?
You move onto your lender's standard variable rate (SVR), often 7% or more. On a £217,000 balance, an SVR of 7.25% instead of a new 4.5% fix costs roughly £500 a month in extra interest. Most lenders let existing customers choose a new deal up to six months before the fix ends, so there is rarely a good reason to spend more than a few days on the SVR.
Can I remortgage if I have retired early?
Switching to a new lender usually means a full affordability assessment based on your income, which can be difficult if you live on ISA withdrawals rather than a salary. A product transfer with your existing lender usually does not need a new affordability check, provided you are not borrowing more or extending the term. Many UK early retirees therefore either take a product transfer or clear the mortgage before leaving work.
Work Out Your Own Numbers
Before your fix ends, find your remaining balance on your latest statement, then model the options:
- Mortgage Overpayment Calculator — enter your new rate and a lump sum at the switch to see the interest saved and your new mortgage-free date
- Mortgage Affordability Calculator — check whether a shorter term or higher payment is realistic on your income before you apply
For more on timing, read lump sum vs monthly overpayments and how overpayments affect your FIRE date.
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