Can You Switch If Your Rate Drops Before You Complete?

You found a rate, your mortgage offer came through, and you felt the relief of having it done. Then three weeks later your lender advertises something cheaper, or a different bank does, and the relief turns into a nagging question. Are you now stuck with the worse deal you signed up for?

Usually not. But the answer depends on your lender, on where you are in the process, and on whether anyone is actually watching. That last part is the bit people underestimate, so let me explain how changing your mortgage rate before completion really works.

Why this is coming up so often right now

Pricing is moving faster than most people expect. Moneyfacts data reported by Mortgage Professional America on 8 October 2026 put the average two year fixed rate at 5.98% on 5 October, the highest since December 2023, with the average five year fix touching 6%. The number of fixed deals priced under 5% fell from almost 1,500 in early September to nine.

When a market moves that quickly it moves in both directions, and lenders reprice some ranges weekly. The Bank of England held base rate at 3.75% on 17 September 2026 with three of nine committee members voting for a rise, and the next decision falls on 5 November. In a market like this, the rate on your offer can stop being the best available surprisingly quickly.

What your mortgage offer actually locks in

A mortgage offer is the lender committing to lend you a stated amount, on a stated product, subject to conditions. It is not a contract you are personally bound into until completion. You are not obliged to draw down the money at all.

That is the important asymmetry. The lender is committed. You are not, at least not until exchange of contracts ties you to the purchase itself. That is what creates the room to switch.

Most offers are valid for three to six months, though new build offers can run up to twelve months, according to mortgage broker John Charcol. Check the expiry date on your own offer letter, because an offer that lapses can mean applying again from scratch.

The three things a lender can do when rates fall

John Charcol sets out three routes, and which one you get depends entirely on your lender's policy and how far along your application is.

They adjust it automatically

Some lenders apply a lower rate to any offer that has not yet completed, with no action needed from you. This is the best outcome and also the least common. It is worth knowing which lenders do this before you apply, not after.

They switch you and reissue the offer

This is the most common route. Many lenders will move you onto the lower rate within the same application and issue a revised offer. Often no new documents are needed. It does add a little time, because the revised offer has to be produced and sent to your solicitor, so it is worth starting the conversation early rather than a week before completion.

They make you apply again

Some lenders treat it as a new application, which means a fresh credit check and a new affordability assessment. That is a materially bigger deal. If your circumstances have changed since you first applied, a new assessment could produce a different answer, so this route needs thinking about rather than jumping at.

The deadlines that decide whether it is possible

Exchange of contracts

This is the one that catches people out. Switching between exchange and completion is generally not advisable, because at that point your completion date is legally fixed and anything that delays the funds creates genuine risk. If you want to look at a better rate, do it before you exchange.

Offer expiry

Counterintuitively, being close to expiry can put you in a slightly stronger position to ask, because the lender has more reason to keep your business. But leaving it that late also leaves no room for anything to go wrong. I would not plan around it.

Lender cut offs

Some lenders restrict switches to a defined window before completion. There is no single industry rule here, which is exactly why it pays to know your specific lender's policy rather than assume.

What it can cost you

A lower headline rate is not automatically a better deal. Before switching, the sums that actually matter are these.

• Arrangement fees. A cheaper rate with a bigger product fee can cost more overall on a smaller loan.
• Administration fees. Some lenders charge a fee for switching product mid application.
• Delay. A reissued offer takes time. If your chain is tight, a modest monthly saving may not be worth the completion risk.
• The size of the saving. John Charcol's worked example takes a £280,000 loan moving from 5.65% to 5.35% over 25 years and estimates a saving of around £45 a month, roughly £540 a year.

On a large loan with a long term, a small rate movement is worth chasing. On a small loan near the end of a term, it often is not. That calculation is the whole job.

Re broking: moving to a different lender entirely

If your own lender will not budge and someone else is materially cheaper, you can start again elsewhere. This is a full new application: new affordability check, new valuation, new underwriting.

There is one rule I would treat as absolute. Keep your existing offer in place until the replacement has been fully issued. Never cancel the bird in the hand. Lenders can decline, valuations can come back short, and circumstances can be read differently by a different underwriter.

This is also where being whole of market genuinely changes the answer rather than just sounding good in a strapline. If your adviser can only see one lender's range, a better rate somewhere else is invisible to them. We cover this properly in our piece on mortgage broker versus bank when rates are rising.

Holding a rate ahead of a remortgage

If you are remortgaging rather than buying, the same logic applies earlier in the process. Many lenders let you reserve a rate a number of months before your current deal ends, and if pricing improves in the meantime it is often possible to move to the better product before you complete.

The practical effect is that you set a floor without giving up the upside. In a market where the average two year fix moved from 5.68% to 5.97% in a single month, having that floor in place matters. Our guide on what to do six months before your deal ends sets out the timeline, and you can read more about how we handle it on our remortgage advice page.

Why nobody tells you your rate dropped

Here is the uncomfortable truth. Your lender has no obligation to ring you and point out that it is now selling something cheaper than the thing it sold you. Neither does your solicitor, who is handling the legal work and is not advising on products.

If nobody is monitoring the market between your offer and your completion, the saving simply does not happen. It is not that anyone acted badly. It is that the job was not assigned to anyone.

That monitoring is part of what a broker is for: tracking lender movements during your application, approaching the lender to request a switch, weighing the saving against fees and delay, and handling the paperwork. Because we are fee free on more than nine in ten of the mortgages we arrange, that ongoing work does not come with a bill attached for most clients. The lender pays us on completion, so checking whether you could do better costs you nothing.

What this means for you

If you have an offer in hand right now, three things are worth doing this week. Find your offer expiry date. Ask whether your lender operates automatic rate reductions or a switch window. And make sure somebody has actually been asked to watch the market on your behalf between now and completion.

If you are about to apply, it is worth asking about a lender's rate switch policy as part of choosing the lender in the first place, not as an afterthought. Two deals at the same rate are not equal if one lender will let you move down and the other will not. If you are still at the start of the process, our explanation of what a mortgage in principle is and is not is a sensible first read, and should I lock in a mortgage rate now covers the timing question.

Frequently asked questions

Can I change my mortgage rate after my offer has been issued?

Often yes, depending on your lender. Some apply lower rates automatically, many will switch you within the same application and reissue the offer, and some treat it as a new application. The route depends on the lender's policy and how far through the process you are.

Is it too late to switch once I have exchanged contracts?

Switching between exchange and completion is generally not advisable, because your completion date is legally fixed at that point and any delay creates real risk. Aim to review the rate before you exchange.

Does switching rates mean a new credit check?

Not always. A product switch within the same application often needs no new documents. Moving to a different lender is a new application, which typically does involve a fresh credit check and affordability assessment.

Will switching delay my completion?

It can. A reissued offer has to be produced and sent to your solicitor. Whether that delay is acceptable depends on your chain and how much you would actually save.

Want someone watching it for you?

If you have an offer sitting in a drawer and you are not sure whether it is still the right one, we will look at it. We search the whole of market rather than one lender's shelf, and for the vast majority of our clients our advice is fee free. You can get in touch here.

Your home may be repossessed if you do not keep up repayments on your mortgage. This article is general information, not personal advice. Lender policies vary and can change. Rates and figures quoted were correct at the dates and sources named.