Exchange of Contracts UK: What It Means & When You're Legally Bound

At a glance

• Exchange of contracts is the moment a residential sale in England and Wales becomes legally binding. Before it, either side can normally walk away.
• GOV.UK is explicit on this point: "An offer is not legally binding until contracts are exchanged."
• The legal requirement for a written, signed contract comes from section 2 of the Law of Property (Miscellaneous Provisions) Act 1989.
• A deposit — commonly around 10% of the price, though this is fixed by the contract rather than by statute — is paid to the seller's solicitor at exchange.
• The completion date is fixed in the contract at the point of exchange and can normally only change by agreement.
• Most exchanges happen by telephone, using one of three standard formulae (known as Formula A, B and C) that fix the exact moment the contract becomes binding.
• After exchange, pulling out is a breach of contract. Under standard contract terms this typically risks the buyer's deposit and, for either side, a further claim for damages.
• This guide covers England and Wales. The position in Scotland and Northern Ireland is different.

What "exchange of contracts" actually means

Exchange of contracts is the formal step where the buyer's solicitor and the seller's solicitor swap identical, signed copies of the sale contract — traditionally by post, though in practice almost always confirmed by telephone using an agreed script. Before exchange, both sides can have agreed a price, instructed solicitors, had surveys done and even set a moving date in conversation, and none of it is legally enforceable. GOV.UK's guidance on buying a home states this plainly: "An offer is not legally binding until contracts are exchanged."

The contract itself sets out the essentials of the deal: the price, the property and its boundaries, which fixtures and fittings are included, any rights or restrictions affecting the property, and the date the sale will complete. GOV.UK's conveyancing guidance describes exchange as the point where "both sides sign final copies and send them to each other," after which "the agreement to sell and buy is legally binding" and, in its words, "usually neither of you can pull out without paying compensation."

When you become legally bound

Exchange is often described as the point of no return, and that description is accurate. From the moment the two signed contracts are exchanged, both buyer and seller are contractually committed to complete the transaction on the agreed date. This is distinct from completion, which is when the purchase money actually moves, ownership formally transfers, and the keys are handed over — usually one to two weeks after exchange, though same-day exchange and completion is possible in some transactions.

The legal basis: section 2 of the 1989 Act

The requirement behind all of this is statutory. Section 2 of the Law of Property (Miscellaneous Provisions) Act 1989 provides that a contract for the sale of an interest in land "can only be made in writing" and must incorporate "all the terms which the parties have expressly agreed" — either in one document, or, where contracts are exchanged, in each of the two documents. The document (or, where contracts are exchanged, at least one of them) must be signed by or on behalf of each party. This is why a verbal agreement, an accepted offer, or even a signed contract sitting unexchanged with your solicitor does not bind you to buy or sell a home — the Act requires the formal exchange step before a binding contract for land exists.

The deposit

A deposit is paid by the buyer at the point of exchange, generally to the seller's solicitor, and is put towards the purchase price at completion. There is no fixed statutory percentage; the amount is whatever the contract specifies. In residential conveyancing, 10% of the purchase price is the long-standing convention, though a smaller deposit — commonly 5% — is sometimes negotiated, particularly where the buyer's own funds are limited. Whatever percentage is agreed, if the buyer subsequently fails to complete, standard contract terms generally entitle the seller to keep the deposit already paid, and the buyer can remain liable for the full deposit amount even if a smaller sum was actually handed over.

How exchange happens in practice: the telephone formulae

Because the solicitors acting for buyer and seller are rarely in the same room, most exchanges now happen over the telephone rather than by physically swapping documents. To avoid any doubt about exactly when a contract becomes binding, solicitors use one of three standard formats, generally known as Formula A, Formula B and Formula C:

• Formula A is used where the buyer's solicitor is already holding the seller's signed contract (for example, because the seller's solicitor posted it over in advance). The buyer's solicitor confirms, on the call, that they hold their own client's signed contract and undertakes to date and send it that day.
• Formula B applies where each solicitor holds only their own client's signed contract. Both solicitors undertake, on the call, to date their contract and send it to the other side that day.
• Formula C is used to coordinate exchange across a chain of related transactions, where several links all need to exchange together. Solicitors agree the terms of exchange on an initial call, then confirm actual exchange has taken place on a follow-up call once every link in the chain is ready.

These formulae are a matter of professional practice rather than a legal requirement, but they are near-universal in residential conveyancing because they create a clear, agreed record of the precise moment a deal became binding — which matters given the consequences that follow.

The completion date

The completion date is negotiated between buyer and seller — usually via their solicitors and estate agents — and is written into the contract before exchange takes place. Once exchanged, that date is fixed and can normally only be changed with both sides' agreement, which in practice is uncommon without a good reason on both sides.

Completion is a separate legal event from exchange. It is only once completion happens that the purchase money is transferred, the seller's mortgage (if any) is repaid, ownership formally passes, and the buyer receives the keys. It's worth noting that time limits which run from "completion," such as the Stamp Duty Land Tax filing and payment deadline of 14 days, run from that later date, not from exchange — a distinction worth keeping straight given how central both dates are to the transaction.

Why chains have to exchange together

Where a buyer is also selling their own home, and that home's buyer is also selling theirs, the transactions form a chain, and every link in the chain typically needs to exchange on the same day for the whole thing to hold together. Before exchange, any single link in a chain can fall through and the rest of the chain has to adjust or collapse. Once every link has exchanged, each individual contract is legally binding on the terms GOV.UK describes, and the risk of the whole chain unravelling drops sharply, because pulling out of any one contract at that point means breaching it. Coordinating simultaneous exchange across a chain is one of the more delicate parts of a conveyancer's job in the run-up to exchange day.

What happens if you pull out after exchange

If you're the buyer

Withdrawing after exchange is a breach of a binding contract. Under the standard contract terms used in most residential transactions, the seller is typically entitled to keep the deposit already paid, and if the seller's actual losses (for example, from having to remarket and resell the property, possibly at a lower price) exceed the deposit, they may be able to claim the shortfall from the buyer as damages.

If you're the seller

If the seller withdraws after exchange, the buyer has legal remedies too. These can include a claim for damages to cover any additional costs or losses caused by the seller's failure to complete, and, in some circumstances, an application to the court for an order of specific performance requiring the sale to go ahead. GOV.UK's summary is consistent with this: once exchanged, "usually neither of you can pull out without paying compensation."

Notice to complete

Sometimes a party is ready to complete on the agreed date and the other is not — because funds haven't arrived, a related transaction in a chain hasn't completed, or some other hold-up. Standard contract terms generally allow the ready party to serve a notice to complete, which sets a further fixed period (commonly ten working days, though this depends on the specific contract terms used) for the other side to complete. If that extended deadline is also missed, the party in default is normally treated as being in breach of contract, which can trigger the consequences described above.

Getting ready to exchange: a practical checklist

1. Get your mortgage offer in place. If you're borrowing, your solicitor will need to see the formal offer and check its conditions before recommending exchange. This step often takes longer than expected, so start early.
2. Commission and review your survey. This is your opportunity to find out about the property's condition, renegotiate, or walk away, all of which become far harder once you're contractually committed.
3. Let your solicitor complete searches and enquiries. Local authority, water and drainage, and environmental searches, plus any enquiries raised with the seller's solicitor, should be resolved before you sign.
4. Sign the contract when you're satisfied. Signing is not the same as exchanging — your signed contract sits with your solicitor until both sides confirm they're ready.
5. Arrange buildings insurance to start from the exchange date. Because risk can pass to the buyer at exchange under standard contract terms, most lenders expect cover to be in place from that day.
6. Agree the completion date with the other side before exchange, since it becomes fixed the moment contracts are exchanged.

After exchange and completion: registering your ownership

Once completion has taken place and you own the property, it must be registered. GOV.UK's guidance on registering land or property with HM Land Registry confirms you must register if you've bought a property, and that, once registered, information including the names of the owners becomes publicly available. Your solicitor or conveyancer normally handles this registration for you as one of the final steps after completion.

This guide provides general information about exchange of contracts in residential conveyancing in England and Wales. It is not legal advice and is not a substitute for advice tailored to your specific transaction and contract terms. The law described was accurate as at July 2026 and is subject to change — always check GOV.UK and legislation.gov.uk for the most current position, and ask your solicitor to confirm how the standard contract conditions in your own transaction apply.

Last reviewed: July 2026 by a non-practising solicitor · Next review due: July 2027 or on legislative change.