Lock-Out Agreements Explained: How to Secure Your Sale

In England and Wales, a property sale is not legally binding until contracts are exchanged. This means that at any point before exchange, the seller can accept a higher offer from another buyer — a practice known as gazumping. A lock-out agreement is the most widely used legal mechanism to reduce that risk, giving the buyer a fixed window of exclusivity during which the seller cannot entertain competing offers.

This guide explains what lock-out agreements are, how they work in practice, whether they are legally enforceable, what they cost, and when they are worth using. It also covers the important distinction between lock-out and lock-in agreements, and how lock-out agreements compare with reservation agreements as an alternative.

What is a lock-out agreement?

A lock-out agreement (sometimes called an exclusivity agreement) is a contract between a seller and a buyer in which the seller agrees not to negotiate with or accept offers from any other party for a specified period. It is a negative obligation — it defines what the seller must not do, rather than what they must do.

Crucially, a lock-out agreement does not oblige the seller to sell the property, nor does it oblige the buyer to buy it. Either party can still withdraw from the sale during or after the lock-out period. The only enforceable commitment is the seller's promise not to deal with third parties for the agreed duration.

A typical lock-out agreement will include the following elements:

• The names of the seller and the buyer
• The property address and title number
• The agreed sale price
• The exclusivity period (a fixed duration, usually expressed as a specific number of weeks or a calendar end date)
• The negative obligation — a clear statement that the seller will not negotiate with, solicit offers from, or enter into any agreement with any person other than the named buyer during the exclusivity period
• Any conditions, such as the buyer being required to instruct a solicitor or submit a mortgage application within a certain timeframe

Legal enforceability: Pitt v PHH Asset Management

The enforceability of lock-out agreements in England and Wales was settled by the Court of Appeal in Pitt v PHH Asset Management [1994] 1 WLR 327. In that case, the seller agreed to sell a property to Mr Pitt and not to negotiate with any other party for two weeks. Within that period, the seller breached the agreement by negotiating with a third party and accepting their higher offer.

The Court of Appeal held that the lock-out agreement was a valid and enforceable contract. The key factors were:

• The agreement was for a definite period (two weeks), not open-ended
• It imposed a clear negative obligation on the seller — not to deal with others — rather than an uncertain positive obligation to negotiate in good faith
• There was consideration from the buyer (proceeding with the purchase and incurring costs in reliance on the agreement)

The Pitt v PHH decision drew a clear distinction between lock-out agreements and lock-in agreements, building on the earlier House of Lords ruling in Walford v Miles [1992] 2 AC 128. Understanding this distinction is essential to knowing what a lock-out agreement can and cannot do.

Lock-out vs lock-in agreements

The difference between a lock-out agreement and a lock-in agreement is one of the most important distinctions in English property law:

In Walford v Miles [1992], the House of Lords held that an agreement to negotiate in good faith was inherently uncertain and therefore unenforceable. Lord Ackner stated that the concept of a duty to negotiate in good faith was “inherently repugnant to the adversarial position of the parties when involved in negotiations.” This principle means that any agreement which tries to compel the parties to continue negotiating, or to reach agreement on specific terms, will not be upheld by the courts.

The practical consequence is clear: if you want a legally enforceable agreement to protect against gazumping, it must be structured as a lock-out agreement (negative obligation, fixed period), not a lock-in agreement.

How long should a lock-out agreement last?

The typical duration for a lock-out agreement is two to four weeks. The period needs to be long enough for the buyer to take meaningful steps towards exchange —instructing a solicitor, submitting a mortgage application, commissioning a survey — but not so long that the seller is locked into an unreasonable commitment.

When deciding on the duration, consider the following factors:

• Buyer's position. A cash buyer with a solicitor already instructed may need only two weeks. A buyer who still needs to arrange a mortgage and sell their own property may need three to four weeks, though a longer period is harder to justify.
• Conveyancing progress. If the seller has already prepared their legal documents (title deeds, property information forms, searches), the buyer's solicitor can start work immediately, and a shorter exclusivity period may be sufficient. For more on typical timelines, see our guide on how long conveyancing takes.
• Market conditions. In a fast-moving market where gazumping is more common, the buyer has a stronger case for a longer lock-out period. In a slower market, the seller may prefer a shorter window.
• Legal requirement. The Pitt v PHH decision makes clear that a lock-out agreement must be for a definite period. An open-ended exclusivity arrangement is not enforceable.

Some lock-out agreements include a provision allowing the seller to extend the period if the buyer is making satisfactory progress. This is permissible as long as any extension is for a further fixed period and both parties agree in writing.

What does a lock-out agreement cost?

The main cost is the solicitor's fee for drafting and reviewing the agreement. Typical legal fees are:

Some conveyancing solicitors will include the lock-out agreement within their standard conveyancing fee if the terms are straightforward. It is worth asking your solicitor upfront whether this is included or charged separately.

Unlike a reservation agreement, a lock-out agreement does not involve a deposit or reservation fee paid by the buyer to the seller. The only financial outlay is the legal cost of preparing the document.

Who benefits from a lock-out agreement?

Lock-out agreements primarily benefit the buyer, but they can also work in the seller's favour in certain situations:

Benefits for the buyer

• Protection against gazumping. The buyer knows the seller cannot accept a higher offer during the exclusivity period, giving them confidence to incur the costs of solicitor fees, surveys, and mortgage applications. See our guide on gazumping and how to protect yourself.
• Reduced financial risk. Without a lock-out agreement, a buyer who spends £1,000 to £2,000 onconveyancing costs risks losing that money if the seller accepts a higher offer.
• Faster progress. Knowing the sale is exclusive, the buyer and their solicitor are likely to prioritise and progress the transaction more quickly.

Benefits for the seller

• Demonstrates commitment. Offering a lock-out agreement signals to the buyer that you are serious about proceeding, which can help secure a strong buyer who might otherwise hesitate.
• Reduces fall-throughs. A buyer who feels protected against gazumping is more likely to proceed to exchange. Fewer fall-throughs means less wasted time and money for the seller.
• Strengthens your negotiating position. When choosing between multiple buyers, offering a lock-out agreement to your preferred buyer can persuade them to accept without pushing for a higher price reduction.

Practical limitations of lock-out agreements

While lock-out agreements are a useful tool, they have significant limitations that sellers and buyers should understand:

• No obligation to complete. The agreement only prevents the seller from dealing with third parties. It does not force the seller to sell or the buyer to buy. Either party can still withdraw from the sale at any time, for any reason.
• Limited damages. If the seller breaches the agreement, the buyer's remedy is damages for wasted costs (typically £1,000 to £3,000 for solicitor fees, surveys, and other expenses). The buyer cannot obtain specific performance — a court order compelling the seller to sell.
• Short window. Two to four weeks is not long enough to reach exchange of contracts in most transactions. Once the lock-out period expires, the seller is free to negotiate with other parties again, and the buyer has no continuing protection.
• Does not prevent gazundering. A lock-out agreement protects against the seller negotiating with others, but it does not prevent the buyer from reducing their offer at a later stage (gazundering).
• Enforcement costs. Pursuing a claim for breach of a lock-out agreement through the courts can be time-consuming and expensive relative to the damages recoverable. In practice, many buyers do not bother to enforce a breach.

Reservation agreements as an alternative

A reservation agreement is a more robust alternative to a lock-out agreement. Where a lock-out agreement relies solely on a negative contractual obligation, a reservation agreement introduces financial consequences for either party withdrawing without good reason.

Here is how they compare:

The Law Commission has previously considered recommending mandatory reservation agreements as part of wider reforms to the home-buying process in England and Wales. While no such requirement has been introduced, the Commission's work highlights the recognised limitations of the current system, in which neither party has any financial commitment until exchange of contracts.

For sellers, the choice between a lock-out agreement and a reservation agreement often depends on the buyer's preference and the value of the transaction. For higher-value sales or situations where fall-through risk is high, a reservation agreement provides stronger protection for both parties.

When a lock-out agreement is worth using

A lock-out agreement is not necessary in every property sale. Here are the situations where it is most likely to be worthwhile:

• Competitive market with gazumping risk. If your property has attracted multiple offers or is in an area where gazumping is common, a lock-out agreement reassures your chosen buyer and reduces the chance of them losing confidence and withdrawing.
• Buyer makes it a condition. Some buyers, particularly those who have been gazumped before, will ask for a lock-out agreement as a condition of proceeding. Refusing may cost you a strong buyer.
• You want to signal commitment. If you have chosen a buyer based on their overall position (chain-free, mortgage agreed, flexible on timing) rather than just the highest price, a lock-out agreement signals that you are committed to them.
• Long gap before exchange. If conveyancing is expected to take longer than usual (for example, due to leasehold complications or a chain), there is a greater window for gazumping and a stronger case for exclusivity.

A lock-out agreement is less useful when you have only one interested buyer (there is no one to gazump you), when the market is slow and competing offers are unlikely, or when the transaction is expected to move very quickly to exchange.

What happens between the lock-out period and exchange?

One of the most common concerns with lock-out agreements is the gap between the expiry of the lock-out period and exchange of contracts. Since most transactions take 12 to 16 weeks from offer to exchange, and a lock-out agreement typically lasts only two to four weeks, there is a significant period during which the seller is free to negotiate with others again.

In practice, this gap is less problematic than it appears. By the time the lock-out period expires, the buyer will have incurred significant costs (solicitor fees, survey fees, search fees) and both parties will have invested time in progressing the transaction. The informal commitment created by this mutual investment, combined with the reputational and practical costs of pulling out, means that most sellers do not re-open negotiations after a lock-out period ends.

If you are concerned about the gap, you have several options:

• Agree a longer initial lock-out period (three to four weeks rather than two)
• Include a provision allowing the lock-out to be extended by mutual written agreement
• Use a reservation agreement instead, which typically runs until exchange and carries financial penalties for withdrawal

How to set up a lock-out agreement

Setting up a lock-out agreement is straightforward. Here is the typical process:

1. Agree in principle. The buyer and seller agree (usually through the estate agent) that they want a lock-out agreement and discuss the key terms: duration, any conditions, and how costs will be shared.
2. Instruct solicitors. One party's solicitor (usually the buyer's, since they benefit most) drafts the agreement. The other party's solicitor reviews it.
3. Sign the agreement. Both parties sign. The agreement must be in writing to be enforceable. The exclusivity period typically starts from the date of signing.
4. Proceed with conveyancing. During the lock-out period, the buyer progresses with their solicitor, mortgage application, and survey. The seller should also ensure their legal paperwork is ready to avoid delays on their side.

The estate agent should be notified that a lock-out agreement is in place. While the agent is not a party to the agreement, they should be instructed not to arrange further viewings or forward offers during the exclusivity period.

Sources

• Pitt v PHH Asset Management [1994] 1 WLR 327 (Court of Appeal)
• Walford v Miles [1992] 2 AC 128 (House of Lords)
• Law Society — Conveyancing Protocol, 5th edition
• Law Commission — Report on Pre-Contract Deposits and Reservation Agreements
• UK Parliament — legislation.gov.uk

Related guides

• Exchange Deposit Explained for Sellers
• How to Deal with Gazunderers

Frequently asked questions