How to Lock a Mortgage Rate in the UK

IMPORTANT: YOUR HOME MAY BE REPOSSESSED IF YOU DO NOT KEEP UP REPAYMENTS ON YOUR MORTGAGE.

In the UK, a mortgage rate is locked when a lender issues a mortgage offer at a stated fixed rate, or when you reserve a new deal ahead of your current one ending. An agreement in principle does not usually lock a rate. The rate you are quoted is only as secure as the stage you have reached, and some products, such as trackers, move even after an offer. This guide explains each stage, how long a rate is normally held, what can end it early, and what to check before you commit.

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TL;DR

A rate is usually secured once your application is complete and an offer is issued, not at the agreement in principle stage.
Lenders commonly hold an accepted offer for around six months. Terms differ by lender, so confirm the validity period in your own offer.
Remortgagers can often reserve a new deal up to six months before the current one ends. Product transfers are often available closer to the end date.
A locked rate can still be withdrawn after a material change, such as a lower valuation or a change in income.
A tracker does not lock in the way a fixed rate does. It follows the Bank of England base rate.

What locking a mortgage rate means
At what stage is the rate actually secured?
How long is a locked rate held?
What can undo a locked rate?
Can you switch if rates fall after you have locked?
Fixed rates and trackers: they do not lock in the same way
What to check before you lock a rate
Locking a rate when your income is not straightforward
Timing: a practical sequence
How we help at Haven Mark Advisers
FAQ
Sources

What locking a mortgage rate means

"Locking" is not a formal regulatory term. Borrowers use it to describe the point at which a lender commits to a specific interest rate for your mortgage, so that later market movements do not change what you pay at the start of the deal.

Nationwide, for example, states that it holds the fixed rate shown in an offer letter or email for six months, unless your circumstances change. If you accept within that period, you start on that rate. That is one lender's policy. Other lenders set their own periods and conditions, so the figure in your offer is the one that applies to you.

In practice, there are three situations where people talk about locking a rate:

Buying a property. You choose a product, apply, and receive an offer. The rate in that offer is the rate you complete on, if the offer remains valid and nothing material changes.
Remortgaging to a new lender. You reserve a product some months before your current deal ends, so that you are not moved to a higher rate by default.
Switching with your existing lender. This is a product transfer or rate switch, which is a different process from a remortgage. It usually involves no new lender, no conveyancing in many cases and a different timetable.

These are not interchangeable. A remortgage means a new lender repays your existing mortgage. A product transfer keeps you with the same lender on a new rate. Each has its own application route, costs and timing.

At what stage is the rate actually secured?

Many borrowers assume the rate is fixed once they have seen it advertised, or once they have an agreement in principle. Neither is the case.

An agreement in principle is an indication of what a lender may be willing to lend, based on limited checks. The BBC reported that it rarely includes a specific rate and is not binding. A specific rate is likely to be secured once the mortgage application is complete and an offer is issued.

A sensible order of events looks like this:

Stage	Is the rate secured?
Browsing or comparing rates	No. Advertised rates can be withdrawn or changed.
Agreement in principle	Rarely. It usually does not commit the lender to a specific rate.
Full application submitted	Depends on the lender. Check what the lender says about the rate at this point.
Mortgage offer issued	Yes, for the fixed rate and period stated in the offer, subject to its conditions.
Completion	The rate in the offer applies from the start of the mortgage.

The application stage varies between lenders. Some reserve a rate at application. Others only commit when the offer is made. Ask the lender, or your adviser, exactly when the product is reserved and what documents the lender needs before it will issue an offer. Delays in documents are one of the common reasons an application slows down. Our guide on fixing mortgage offer delays sets out the steps that help keep a case moving.

How long is a locked rate held?

The period depends on the lender and the product. An accepted offer is usually held for around six months, according to This is Money. Some lenders use shorter or longer periods, and new build offers can have different terms because completion dates depend on construction. Read the offer document for the date it expires.

Reserving a remortgage deal early

If your fixed term is ending, you can usually arrange the next deal before it does. MoneySavingExpert says that borrowers can often reserve a remortgage deal up to six months before the current deal ends, and that product transfers with your existing lender are often available around three months ahead. Booking fees, commonly £100 to £250 according to the same source, may be payable upfront and may not be refundable, so check this before you reserve.

Remortgage booking windows and fee range

The reason to act early is the alternative. If you do nothing when your initial rate period ends, MoneyHelper explains that you are normally moved to the lender's reversion rate, typically the standard variable rate, which is often higher than a fixed rate.

If the offer expires before completion

If completion is delayed beyond the offer's validity, the rate may no longer be available. Lenders have different policies on extending an offer, and some will extend only once or only for a limited time. If you can see that the conveyancing is running slowly, tell your adviser early. Our article on extending a UK mortgage offer without reapplying explains what lenders typically look at when you ask.

What can undo a locked rate?

A locked rate is a commitment subject to conditions. A lender may withdraw or change an offer after a material change. This is Money lists examples including a lower property valuation, new income information, evidence of fraud or newly identified legal issues with the property. Nationwide's wording is similar: the rate is held unless your circumstances change.

In practical terms:

Valuation. If the lender's valuer values the property below the price you agreed, the loan-to-value changes. The lender may reduce the amount it offers or move you to a different product, and the rate can be different.
Employment or income. If you change job, move from employed to self-employed, or your income drops between application and completion, tell your adviser straight away. A known future change must be disclosed. Withholding it can lead to the offer being withdrawn and may cause serious problems later.
Credit commitments. New borrowing, such as a car finance agreement or a credit card, can alter the affordability picture. Check with your adviser before taking on anything new.
Legal issues. Problems with title, a lease or planning can lead a lender to reconsider.

None of this means a rate is unreliable. It means the rate is secure for the mortgage you applied for, on the facts you gave. Accurate information at the start is what protects it.

Can you switch if rates fall after you have locked?

Borrowers often ask whether locking early removes the chance of a better deal. For remortgages and rate switches, it often does not. A reserved deal can frequently be replaced if a cheaper product becomes available before the new deal starts, but this depends on the lender and on whether you have paid non-refundable fees. Ask these questions before reserving:

Can I change to another product from the same lender before the deal starts?
Is any booking or arrangement fee refundable if I cancel or switch?
What happens to my offer if I submit a new application elsewhere?

For a house purchase, switching is harder. A new application with another lender means fresh checks, a new valuation in many cases and possible delay to your completion date. Compare the saving against the cost of delay, including any risk to the purchase itself.

The This is Money article from October 2022 recommended comparing rates, speaking to a broker and considering locking, particularly if your deal ends within six to nine months. It describes conditions at that time, and rates have moved since. The principle that matters is that a decision to lock should rest on your circumstances and the available terms, not on a forecast of where rates will go.

Fixed rates and trackers: they do not lock in the same way

A fixed rate stays the same for the length of the deal. Nationwide states that a fixed rate and payments remain unchanged during the fixed deal, while a tracker moves in line with the relevant base rate.

The same page explains that for a tracker, the rate changes in line with the Bank of England base rate upon completion. The rate on your mortgage when you complete can therefore differ from the one quoted at application. If you want certainty about your starting payment, a fixed rate is the product that provides it. If you are weighing the two, our practical view on fixed versus tracker mortgages covers the trade-offs in more detail.

Two years or five years?

Two- and five-year fixes are the most common terms. A shorter fix gives you the chance to re-price sooner. A longer fix gives certainty for longer, although you may face an early repayment charge if you want to leave it before it ends. The right choice depends on how long you expect to stay in the property, how tight your budget is, and whether you may need to sell, move or borrow more.

The FCA notes that if a fixed-rate term is shorter than five years, lenders must stress test affordability against possible future interest rates. This means the amount a lender will offer on a two-year fix may be assessed differently from a five-year product. Your adviser can show how the term you choose affects the maximum borrowing at the lenders suitable for you, without any assurance that a particular lender will accept your application.

What to check before you lock a rate

A lower headline rate does not always mean a better deal. MoneyHelper's guidance on remortgaging to cut costs points to affordability, eligibility, loan-to-value, early repayment charges, fees on the new deal, and legal, valuation and administration costs. Work through this list before you commit:

Total cost, not just the rate. Add product fees, booking fees and any valuation or legal costs, and compare over the length of the deal.
Early repayment charges. Check whether leaving your current deal early triggers a charge, and whether the new deal has one.
Loan-to-value. A change in property value or in the size of the loan can move you into a different pricing band.
Affordability. Every regulated lender must assess creditworthiness and affordability. Prepare for the level of evidence needed, especially if your income is not a standard salary.
The offer's expiry date. Match it to the realistic completion date, with room for delay.
Your plans. If you may move within the fixed period, ask whether the mortgage is portable.

Porting an existing mortgage

Porting means moving your current mortgage deal to a new property. MoneyHelper states that a portable mortgage still requires affordability approval when moved, and that borrowing additional money normally involves a new mortgage deal with potentially different terms. So porting keeps your existing rate on the amount you already borrow, but is not automatic and not a guarantee.

Locking a rate when your income is not straightforward

A rate can only be secured on an application that the lender is willing to approve. For employed borrowers on a standard contract, the evidence is generally payslips and a contract. For others, lenders ask for different evidence, and they differ in how they treat it.

Self-employed and company directors. Lenders commonly ask for tax calculations and tax year overviews, and some also ask for accounts. The documents they accept and the income figure they use vary by lender.
Contractors. Some lenders consider a day rate, others look at contract history. Our guide on contractor mortgages sets out how lenders commonly approach this.
Fixed-term contracts. Lender attitudes depend on the contract length and your track record. See what England lenders expect on fixed term contracts.
Foreign nationals and visa holders. Residency status, deposit and credit history affect which lenders may be suitable. Our pages on UK visa and foreign national mortgages explain the typical considerations.

It is not safe to treat one lender's criteria as the rule across the market. A rate is only useful if the lender chosen is one that can accept your income structure. Securing a low rate with a lender whose criteria you do not meet leads to a declined application and lost time. Selecting the lender first, then the product, is the safer order.

Timing: a practical sequence

For a remortgage, a workable timetable looks like this:

Six to nine months before the end date. Check your current deal's end date, early repayment charge position and balance. Gather income documents.
Up to six months before. Compare available products and, if suitable, reserve one. Confirm fees and whether they are refundable.
After reserving. Complete the application and valuation, and keep documents current. Monitor the market if your lender allows a product change.
Before the old deal ends. Complete, so that you move straight on to the new rate and avoid the reversion rate.

For a purchase, the order is different: agree the budget and evidence, obtain an agreement in principle, find the property, apply in full, and receive the offer. Get the offer date and the expected exchange and completion dates side by side as soon as you know them.

How we help at Haven Mark Advisers

At Haven Mark Advisers, each client works with one dedicated adviser from first conversation to completion. That adviser compares suitable lenders for your income and circumstances, manages the application and keeps track of offer expiry dates, so that the rate you choose is still available when you complete.

Our purchase mortgage service costs £495 and our remortgage service costs £195, each a one-off fee. We may also receive commission from lenders. The fees and how we are paid page explains this in full. If your fixed deal is ending, our remortgage advice and rate switch and product transfer pages set out how each route works.

Haven Mark Advisers

We cannot guarantee eligibility, acceptance, borrowing amounts or rates. What we can do is explain the options clearly, tell you which stage of the process secures a rate with a given lender, and manage the case actively. To discuss your situation, start at Haven Mark Advisers.

FAQ

Is a mortgage rate locked when I get an agreement in principle?

Usually not. An agreement in principle is an early indication and, according to the BBC, rarely includes a specific rate. The rate is more likely to be secured once your application is complete and the lender issues an offer.

How long does a mortgage offer last?

An accepted offer is commonly held for around six months, but it varies by lender and product. Your offer letter states the exact expiry date. If completion may run past it, speak to your adviser early about whether the lender can extend.

Can I lock a remortgage rate before my current deal ends?

Often, yes. MoneySavingExpert says that borrowers can often reserve up to six months ahead, with product transfers commonly available around three months ahead. Check for booking fees, which may be non-refundable.

Can a lender withdraw an offer after I have locked a rate?

Yes, in some circumstances. A lower valuation, a change in your income, evidence of fraud or a legal issue with the property can all lead a lender to reconsider, as set out by This is Money. Always tell your adviser about any change in your circumstances, including changes you expect.

Does a tracker mortgage lock in the rate?

No. A tracker follows the Bank of England base rate, so the rate at completion can differ from the rate quoted at application, as Nationwide explains. A fixed rate keeps the same rate and payments for the fixed period.