Will mortgage rates go up if the Bank of England raises interest rates in September 2026?

Not necessarily, and that's the point: fixed mortgage rates have already risen this week without the Bank of England moving at all. Five-year swap rates, the wholesale cost lenders actually price fixed deals against, climbed above 4.5% in early September, their highest level in around three years, and Nationwide, Halifax, Barclays, Santander and HSBC have all raised selected fixed rates in response (mortgage market reporting, September 2026). If the Monetary Policy Committee does raise Bank Rate on 17 September, that mainly hits tracker and standard variable rate borrowers immediately, while fixed rates move on swap-rate expectations that often shift before and after the announcement rather than on the day itself. A hold isn't a guarantee that fixed pricing stays where it is.

What happens to my mortgage if the Bank of England base rate rises?

If you're on a tracker mortgage, your rate moves in line with Bank Rate automatically, usually within one to two months, so a 0.25 percentage point rise adds a predictable amount to your monthly payment straight away. If you're on your lender's standard variable rate, the change usually follows within weeks, though SVRs already sit far above Bank Rate at around 7.13% on average, so the proportional impact is smaller than it looks (Moneyfacts/HomeOwners Alliance, September 2026). If you're on a fixed rate, nothing changes until that fix ends, but the rate you're offered for your next fix is priced off swap rates and market expectations, which can move well before or after the Bank's own decision. That's why homeowners with a fix ending in the next few months are watching this month's meeting rather than those with two or three years still to run.

Can I lock in a mortgage rate before my current fix ends?

Yes. Most UK lenders let you reserve a new mortgage rate three to six months before your existing fix expires, and the reservation itself is normally free. If a cheaper rate becomes available with the same lender before your new deal actually starts, most lenders will let you switch down to it at no extra cost, so reserving today's rate rarely locks you out of a better deal appearing later. What it does do is protect you if rates rise instead, which is the asymmetry that matters right now: the downside of reserving early is small, and the potential downside of waiting and being wrong is larger. Check your specific lender's switch-down policy and reservation window before assuming it applies, since terms vary.

Why are mortgage rates rising if the Bank of England hasn't moved?

Fixed mortgage rates are not priced directly off Bank Rate. Lenders price them against swap rates, which reflect where financial markets expect interest rates to average over the life of the fix, so swap rates move constantly on inflation data, growth figures and shifting bets about future Bank of England decisions. Five-year swap rates rose above 4.5% in early September 2026, a three-year high, after markets started pricing in a real chance the Monetary Policy Committee's hawkish minority grows large enough to vote for a rise, following inflation's climb to 2.9% in July. Lenders reprice their fixed ranges to track that cost, which is why Nationwide, Halifax and others raised rates this week even though Bank Rate itself is still sitting at 3.75%, unchanged since 30 July.

£31 a month rides on locking in before 17 September

You have been checking mortgage comparison sites most weeks since your fix started running down, telling yourself you will lock in "when it feels like the right moment." This week you finally opened one of those tabs and the number had moved the wrong way. Nothing has actually happened yet, the Bank of England hasn't met, the base rate hasn't changed, and you're left wondering whether you just missed the best rate you were ever going to get, or whether you should still hold out for the 17 September decision before doing anything.

Here's what's actually going on: the best-buy two-year fixed mortgage rate rose from 4.34% to 4.40% this week, and the five-year equivalent rose from 4.38% to 4.48%, before the Bank of England's Monetary Policy Committee has made any decision at all (HomeOwners Alliance, 10 September 2026). On a £220,000 mortgage, waiting for a further move of similar size the wrong way would cost you roughly £31 a month more than locking in today. Waiting for rates to drift back down instead would save you around £12 a month. That gap is the whole decision.

Why rates already moved without the Bank doing anything

Fixed mortgage rates are not priced off Bank Rate directly. Lenders price them against swap rates, the wholesale cost of borrowing over the life of the fix, and those move on what the market expects the Bank to do next, not on what it has actually done. Five-year swap rates climbed above 4.5% in early September 2026, their highest level in roughly three years, and Nationwide, Halifax, Barclays, Santander and HSBC have all raised selected fixed rates in response this week, reversing cuts several of them made as recently as early August (mortgage market reporting, September 2026).

That reversal matters more than it might look, because it shows the market moving ahead of the actual event. The Bank Rate itself has sat at 3.75% since 30 July and hasn't shifted (Bank of England MPC calendar), but the fixed-rate mortgage market has already started pricing in the possibility of a rise regardless. Our recent piece on why swap rates can push mortgage rates up without a base rate move covers the mechanism in more detail if you want the fuller explanation.

So if you were planning to wait until 17 September to see "which way rates go" before deciding anything, that plan has already been overtaken: the market has been repricing all week, and there's no reason to assume it waits politely for the announcement either.

What the Bank might actually do on 17 September

Most forecasters still expect the Monetary Policy Committee to hold Bank Rate at 3.75% on 17 September, with market-implied pricing putting the odds of no change at roughly 90% (rate-probability tracking, September 2026). But the committee's hawkish minority has grown for three meetings running: in July it voted 6-3 to hold, with three members, Megan Greene, Catherine Mann and Huw Pill, each backing an immediate rise to 4.00% (Bank of England MPC minutes, July 2026). Inflation has moved in their direction since then, climbing from 2.6% to 2.9% in the year to July, even though core CPI held at 2.6% and services inflation actually eased slightly to 3.4% from 3.6% (ONS CPI, July 2026), a genuinely mixed picture rather than a clean case either way.

A hold remains the more likely outcome. But a hold at the meeting and a hold in mortgage pricing are two different things, and this week is the proof: fixed rates rose before the vote even happened. If the hawkish minority grows to a majority, or simply gets loud enough to shift market expectations further, swap rates and fixed mortgage pricing could easily move again regardless of what the committee actually decides on the day.

So the real risk to weigh isn't really "will the Bank raise rates on 17 September," it's "will the market keep pricing in that possibility between now and whenever your new fix would actually start," and this week already answered that question once.

The maths: what waiting could cost you

Take a fairly typical £220,000 repayment mortgage with 25 years remaining. Locking in today's best-buy two-year fix at 4.40% costs £1,210 a month. If fixed rates ease back over the coming weeks to roughly where they sat before this week's rise, say 4.30%, your payment would be about £1,198 a month, a saving of £12 versus locking in now. If instead lenders reprice by a similar amount again, say to 4.65%, taking the rise further, your payment would be about £1,242 a month, £31 more than locking in today.

The maths, in one place (£220,000 mortgage, 25-year term):

Lock in now at 4.40%: £1,210/month.
If rates ease to roughly 4.30%: £1,198/month (£12 a month better off waiting).
If rates rise a further 0.25 points to roughly 4.65%: £1,242/month (£31 a month worse off waiting).
Break-even: waiting only pays off if there's better than a roughly 72% chance rates ease rather than rise from here. A base-rate hold on 17 September doesn't by itself deliver that; this week's repricing happened without one.

That break-even point comes from weighing the £12 upside against the £31 downside: for waiting to be the better bet on average, you would need better than roughly a 72% chance that fixed rates fall rather than rise over the next few weeks. Given that lenders have been repricing upward, not downward, for the better part of a week, and the Bank's own rate-setters have grown more hawkish for three straight meetings, that's a harder case to make than "just wait and see" usually assumes.

So on a mortgage of this size, the risk of waiting isn't symmetrical: a further rise realistically costs you more than a further fall would save you, which tilts the maths toward locking in rather than holding out for the announcement.

How to lock in without losing flexibility

The good news is that locking in now doesn't mean committing blind. Most lenders let you reserve a rate three to six months before your current fix ends, at no cost to reserve, and if a cheaper rate appears with the same lender before your new deal actually starts, most will let you switch down to it for free. That mechanic is exactly what removes the downside from acting early: you're not betting your rate on today's number staying the best one available, you're protecting yourself against it getting worse while keeping the door open if it gets better. Our remortgage preparation guide walks through how to check your loan-to-value band and get your paperwork ready before you reserve anything.

This is also worth separating from the standard variable rate trap. If your fix lapses before you have anything new in place, you fall onto your lender's SVR, averaging 7.13% right now (Moneyfacts/HomeOwners Alliance, September 2026), which on the same £220,000 mortgage runs to roughly £1,573 a month, hundreds more than any fixed option on the table. We covered the scale of that specific risk in our piece on the SVR shock facing over a million homeowners this year, and it's a separate, larger danger from the smaller swap-rate-driven gap discussed here: reserving a rate early solves both at once.

So if your fix ends within the next six months, the practical move is to reserve a rate now rather than wait for 17 September, because the reservation itself costs nothing and protects you from exactly the kind of mid-week repricing that just happened.

What this means for you

Frankly, if your current fix has less than about six months left to run, the maths points toward reserving a rate now rather than waiting for the Bank's 17 September decision to "see which way things go," because the fixed-rate market has already moved this week without any decision being made at all. Most people who run these numbers end up locking in something, even if it isn't the very cheapest rate they will ever see, because a free-to-reserve, free-to-switch-down deal has almost no downside against a real risk of paying £31 a month more if pricing keeps drifting the way it has all week. If you have longer than six months left on your current deal, there's less urgency, but it's still worth checking whether your lender offers an early reservation window, since the same asymmetry applies whenever you eventually come to use it. If you're also weighing up whether to fix for two years or five once you do lock in, that's a separate decision worth reading alongside this one, but it shouldn't be the reason you delay reserving a rate in the first place.