New Build Exchange of Contracts: What Happens and What Buyers Should Check

Exchanging contracts is one of the biggest commitment points when buying a new build. You may have reserved the property only a few weeks earlier, yet the developer can expect you to exchange while the home is still under construction and before you have seen the finished plot.

That is why the exchange stage deserves more attention than simply meeting the developer's deadline. Before you commit, you need to understand exactly what you are buying, what the contract says about completion, whether your mortgage will remain valid and what happens if the build programme changes.

If you are still deciding whether to reserve, start with our new build reservation fee and agreement guide. Buyers purchasing before the property is finished should also read the off-plan new build checklist.

What does exchange of contracts mean on a new build?

In England and Wales, exchange of contracts is the point at which the buyer and seller become legally committed to the transaction. The government's home-buying guidance explains that an accepted offer is not legally binding until contracts are exchanged. Northern Ireland also uses an exchange-of-contracts process. Scotland has a different conveyancing system, where the legally binding agreement is normally formed through concluded missives, so Scottish buyers should ask their solicitor to explain the equivalent stage for their purchase.

For a new build, exchange can feel unusually early because the home may not yet be complete. You are committing to the property described by the plans, specification, legal documents and contract rather than simply the finished home you can see on the day.

How quickly do you have to exchange on a new build?

New build developers often work to a relatively short reservation-to-exchange timetable. The exact deadline is development-specific and should be set out in your reservation information. Do not assume that a sales team's preferred timetable overrides the legal and financial checks you need to complete.

For homes covered by the New Homes Quality Code, the reservation documentation includes information about the expected exchange date. The current Code version applies to qualifying homes reserved from registered developers from 2 March 2026. Your conveyancer should tell you which consumer code or scheme applies to your plot.

If the exchange date is approaching and searches, mortgage work or legal enquiries are outstanding, speak to your conveyancer and the sales team early. A requested extension is not guaranteed, but silence is usually less useful than explaining what remains outstanding and when it is expected.

What should be complete before you exchange?

Your conveyancer is responsible for advising you on the legal position, but as the buyer you should also be able to explain the major parts of the deal in plain English. Before exchange, make sure the important commercial details you relied on during the sales process have made it into the written documents where appropriate.

• The exact property, plot number and agreed purchase price.

• The tenure and any lease, rentcharge, service charge or estate-management obligations.

• The written specification for the home and any agreed upgrades.

• Parking spaces, garages, boundaries and rights that are important to the plot.

• Developer incentives, contributions or extras included in the transaction.

• The new-home warranty provider and the documents available at this stage.

• The expected completion window and the process for giving notice when the home is ready.

• Any long-stop provisions or other contractual protections relating to significant delay.

• The mortgage offer, valuation and lender requirements.

• The amount of deposit required at exchange and where the money will be held.

If any answer is unclear, ask your conveyancer before authorising exchange. Sales brochures, conversations in a marketing suite and show-home features should not be treated as substitutes for the documents that govern your purchase.

How much deposit do you pay when exchanging on a new build?

The exchange deposit is not necessarily the same thing as the reservation fee or the deposit percentage you discuss with a mortgage lender. The contract will set out what must be paid on exchange and how any reservation money already paid is treated.

Do not transfer a large deposit because a sales adviser tells you a figure verbally. Your solicitor or conveyancer should confirm the amount, payment instructions and timing. Property transactions are also a target for payment fraud, so independently verify bank details using the process recommended by your legal firm before sending funds.

Can you exchange before your new build mortgage is ready?

Treat this as a major risk question rather than an administrative detail. Once you exchange, you are making a binding commitment, so you need to know how the purchase will be funded at completion.

New build timing can be difficult because a mortgage offer may expire while construction continues. Our new build mortgage guide explains offer validity, valuations, incentives and what buyers should ask when the completion date is uncertain.

Before exchange, confirm with your lender or mortgage adviser how long the offer remains valid, whether it covers the expected build window and what could happen if the developer is late. Do not assume that an extension will automatically be available.

What is completion on notice?

With a completed resale property, exchange and completion can be linked to a fixed date. An off-plan new build may work differently because the developer does not yet know the exact day the property will be ready.

The contract can therefore provide for completion to take place after formal notice is served once the relevant completion conditions have been met. Your conveyancer should explain how much notice you will receive, what triggers that notice and how quickly funds must be available afterwards.

This matters for buyers who need to give notice on rented accommodation, organise removals, sell another home or make sure a mortgage offer is still live. If your build has already slipped, read what happens when a new build completion is delayed.

What should you check about the completion date before exchange?

Ask your conveyancer to separate the sales estimate from the contractual position. A sales adviser might talk about a month, season or quarter, while the legal contract may allow a wider window before stronger remedies become available.

• What completion estimate has the developer provided today?

• How will that estimate become more precise as construction progresses?

• How much notice of legal completion can the developer give?

• Does the contract include a long-stop date or another mechanism for serious delay?

• What happens to your deposit if the transaction can be ended under the contract?

• Could a delay take you beyond your mortgage-offer expiry date?

• Which costs should you avoid committing to until the legal completion date is confirmed?

Should you inspect the property before exchange?

On an early off-plan purchase, a meaningful inspection may not be possible before exchange because the home is not finished. That makes the paperwork, developer research and later pre-completion inspection especially important.

Research the housebuilder before you commit. Use the new build developer directory and UK new build developer rankings to compare published satisfaction data and third-party review context. National data cannot predict the quality of one plot, but it can help you ask better questions about aftercare and customer experience.

Closer to completion, ask what access you will receive and whether you can arrange an independent pre-completion inspection. Our guide to whether a snagging survey is worth it explains how professional snagging fits into the process.

What happens if you pull out after exchanging contracts?

Because exchange creates a legal commitment in England and Wales, withdrawing afterwards can have serious financial consequences. The outcome depends on the contract and circumstances, including what happens to the deposit and whether additional losses can be claimed.

Do not rely on a general online answer for a decision at this stage. If you are considering withdrawing, speak to your conveyancer urgently and ask them to explain your contract before taking action.

New build exchange checklist

Before telling your conveyancer that you are ready to exchange, make sure you can answer these questions:

• Have I received and understood the written specification for my exact plot?

• Do I know which extras and incentives are included in the agreed purchase?

• Has my conveyancer explained the tenure, estate charges and other ongoing obligations?

• Is my mortgage position sufficiently secure for the expected completion timetable?

• Do I know how much deposit is due at exchange?

• Do I understand completion on notice and the amount of notice I could receive?

• Do I understand what the contract says about significant delays?

• Have I checked the developer's current ratings, reviews and after-sales context?

• Do I know what warranty applies to the property?

• Have I avoided relying on verbal promises that are not reflected in the paperwork?

The bottom line

Exchanging contracts on a new build is not just the next box after reservation. It is the point where the information you have gathered about the property, developer, mortgage, costs and completion timetable becomes a legal commitment.

Use the developer's deadline as a reason to stay organised, not as a reason to skip questions. Get the important details in writing, make sure your conveyancer has explained the contract, confirm your mortgage position and understand exactly how completion will work before you exchange.

Continue your research with the new build buyer guides, developer profiles and latest housebuilder rankings.