Five years ago, plenty of buyers locked in a mortgage rate that started with a 1. Nationwide, Halifax and Barclays were all offering five-year fixes below 2% through most of 2021, and anyone who remortgaged or completed a purchase that year effectively froze their monthly payment at a level the market hasn't seen since. That freeze is thawing now. Lenders typically write to borrowers three to six months before a fixed deal ends, which means the letters landing on doormats this August and September belong to exactly that 2021 vintage — and the gap between what people were paying and what they're about to pay is the largest of any renewal cycle in over a decade.
The scale is easy to underestimate from a single household's perspective, so it helps to look at the shape of the problem rather than one bill. Roughly 1.6 million fixed-rate deals are due to expire across the UK in the second half of 2026, according to UK Finance's mortgage lending figures, and a disproportionate share of those were written in the low-rate window between January 2021 and December 2021. Someone on a £220,000 mortgage who fixed at 1.39% in autumn 2021 was paying around £873 a month on a 25-year term. Move that same balance onto a typical five-year fix available today, somewhere around 4.2%, and the payment rises to roughly £1,180 — nearly £307 more a month, before anyone has even considered whether they overpaid during the cheap years or extended the term to soften the blow.
Product Transfer or Full Remortgage — the Choice Most Borrowers Get Wrong
When the renewal letter arrives, most lenders make the easy option look like the only option. A product transfer — switching to a new rate with your existing lender, with no new affordability checks, no solicitor and usually no valuation — can be arranged online in about fifteen minutes. A full remortgage to a different lender takes six to eight weeks, involves a fresh credit check, and usually costs £300–£500 in legal and valuation fees even when a lender offers "free" conveyancing as an incentive. Given the choice between a form you can fill in on your phone and a process that drags into a second month, most people take the product transfer without comparing it against the wider market.
That's usually the wrong call. Product transfer rates sit on average 0.15–0.35 percentage points above the best remortgage deals for an equivalent loan-to-value, because the lender knows inertia is working in its favour and prices accordingly. On a £220,000 balance, a quarter of a percentage point is close to £45 a month — not dramatic on its own, but it compounds over a two- or five-year term into a four-figure sum for doing nothing more than accepting the first offer in the inbox. Brokers such as L&C Mortgages and Habito will run a whole-of-market comparison for free, and MoneySavingExpert's mortgage calculator takes under five minutes to tell you whether your lender's "loyalty" rate is actually competitive.
Where Early Repayment Charges Actually Bite
None of this applies if your current deal hasn't technically ended yet. Early repayment charges on most fixed products taper from around 5% of the outstanding balance in year one down to 1% in the final year, and they apply the moment you redeem the mortgage early — including to switch to a cheaper rate with the same lender. The one genuine exception is that most lenders let you lock in a new deal up to six months before your current one expires, with the new rate only kicking in once the old one ends, and no ERC charged in that window. Miss that window and revert to the standard variable rate even for a single month, and you'll typically pay 7.5–7.99% — more than either a product transfer or a remortgage would have cost, on a rate that resets monthly rather than being fixed for years.
What the New Rate Actually Looks Like
Two-year fixes are currently pricing a little higher than five-year ones, which is unusual by historical standards and reflects continued uncertainty about where the Bank of England base rate settles over the next eighteen months. Skipton and Coventry Building Society are both offering five-year fixes in the 3.9–4.3% range for borrowers with 25% equity or more, while two-year equivalents sit closer to 4.4–4.8%. That inverted pricing means the "safe" short-term option now costs more than committing for longer — the opposite of what most homeowners instinctively expect, and worth checking explicitly with a broker rather than assuming a shorter fix is automatically cheaper.
Borrowers with less equity face a steeper curve. Anyone remortgaging at 90% loan-to-value is typically looking at rates a full percentage point or more above someone at 60%, which matters most for buyers who purchased in 2021 with a smaller deposit and haven't had years of price growth to build equity since. If your loan-to-value has crept above 85% — either because the mortgage balance barely moved during an interest-only or low-overpayment period, or because a valuation has come back lower than the 2021 purchase price — get that number confirmed with an actual valuation before you start comparing rates, not after.
Landlords Are Working a Harder Version of the Same Sum
Buy-to-let renewals compound every one of these pressures. A landlord who fixed at 2.5% in 2021 and is now offered 5.1% isn't just facing a bigger bill — they're facing a lender that recalculates whether the property's rent still covers the mortgage at the new rate, and that calculation has got noticeably less forgiving since 2021.
Stress Tests Haven't Loosened Much
Most buy-to-let lenders require rental income to cover 125–145% of the mortgage payment calculated at a stress rate around 7.5%, regardless of the actual rate on offer, and higher-rate taxpayers usually sit at the top of that range. A property earning £1,400 a month in rent against a £900 mortgage payment looked comfortably affordable in 2021. Run the same numbers at today's rates and stress margin, and some landlords find the sums no longer clear the lender's bar — not because the rent has fallen, but because the stress test recalculates against a materially higher assumed rate. Some are selling. Others are switching to interest-only where the lender allows it, accepting a lower monthly outlay in exchange for not reducing the capital balance, which only postpones the arithmetic rather than solving it.
Landlords with several properties on staggered renewal dates have an advantage here that single-property owners don't: they can use the first renewal as a rehearsal. Work through the actual figures on the smallest or simplest mortgage first, confirm which lenders will still stress-test favourably against the current rent roll, and treat that as a template for the harder decisions on the rest of the portfolio.
What to Do in the Six Weeks Before Your Deal Ends
Start the comparison process the moment the renewal letter lands, not the week the old rate expires. Rates move week to week, and locking in early — most lenders let you reserve a rate up to six months ahead — protects against further increases without costing anything if a better deal appears closer to the switch date; most product-transfer and remortgage offers can be swapped for a cheaper one right up until completion, at no charge.
- Get an up-to-date valuation before assuming your loan-to-value band — a property that's gained even modest value since 2021 might qualify for a meaningfully better rate tier.
- Compare the product transfer your lender offers against at least two whole-of-market quotes from a broker; the fifteen-minute option is rarely the cheapest one.
- Ask specifically about porting versus switching if you're planning to move house within the fix term — the rules differ by lender and get complicated fast.
- Check whether overpaying now, while still on the old rate, reduces the balance enough to shift you into a lower loan-to-value band for the new deal.
Don't wait for the "best" moment to fix, because there isn't one — nobody can reliably call the bottom of a rate cycle, and the cost of guessing wrong is a mortgage sitting on the lender's standard variable rate while you wait. Lock in a rate you can afford within the six-month reservation window, keep the option open to switch to something cheaper before completion, and treat the renewal letter as the start of a five- or six-week task rather than a form to sign on the day it arrives.