Exchange and Completion Explained: What They Mean

Exchange and completion are the two legal milestones that turn an accepted offer into a home you own. Exchange of contracts is the moment your purchase becomes legally binding: both sides are committed, a completion date is fixed, and pulling out now means losing your deposit. Completion is the day ownership actually transfers — the money moves, the seller leaves, and you collect the keys. In short: exchange is when you are legally committed; completion is when you move in. They usually happen one to four weeks apart, and understanding the difference removes most of the anxiety from the final stretch of buying.

This guide walks through exactly what happens at each stage, why there is a gap between them, the deposit you pay at exchange, when your buildings insurance must start, and the handful of things that can still go wrong once you are this close.

What is exchange of contracts?

Exchange of contracts is the point at which your purchase becomes legally binding in England, Wales and Northern Ireland. Up until this moment, either you or the seller can walk away for any reason without penalty — which is what makes gazumping possible. At exchange, your conveyancer and the seller's conveyancer swap signed, identical copies of the contract (in practice over the phone, reading the terms to each other and recording the time), and a completion date is written into the contract. From that second, both parties are legally locked in.

Several things must be in place before your conveyancer will let you exchange: a formal mortgage offer in hand, all searches back and satisfactory, enquiries with the seller's side resolved, the survey reviewed, and your deposit funds cleared in the conveyancer's account. Your conveyancer will not exchange until they are confident nothing outstanding could unravel the purchase, because after exchange there is no easy way out.

The deposit you pay at exchange

At exchange you pay a deposit — typically around 10% of the purchase price — to your conveyancer, who holds or passes it on as part of the contract. This is not an extra cost on top of your savings: it forms part of the deposit you have already been building, and the balance is settled at completion. It is separate from, but related to, the overall deposit your mortgage lender requires.

The exchange deposit matters because it is what you stand to lose if you fail to complete. If you pull out after exchange, the seller can keep this deposit and may pursue you for further losses. In some chains where a buyer's own funds are tied up further along, conveyancers agree a reduced deposit, but the default expectation is around 10%.

• The exchange deposit is usually around 10% of the purchase price
• It is paid to your conveyancer, not handed to the seller directly
• It counts towards your overall deposit — not an additional sum
• Lose it if you pull out after exchange, along with possible further liability
• A lower deposit can sometimes be negotiated within a chain

Buildings insurance must start at exchange

One detail catches many first-time buyers out: your buildings insurance must be in place from the moment you exchange, not from completion. The reason is that once contracts are exchanged you are contractually committed to buy the property, so you carry the risk if it is damaged — by fire, flood or storm — in the gap before you move in. Most mortgage lenders make buildings cover a condition of the loan and will expect a policy live from exchange.

Arrange the policy in advance so it can start on the exchange date. You do not need to be living there for cover to apply; you insure the structure from the day you become legally bound to buy it. Leaving this until completion day is a common and avoidable mistake.

What is completion?

Completion is the day ownership legally transfers and you become the owner. On completion, the balance of the purchase money is sent from your conveyancer to the seller's conveyancer, usually by same-day bank transfer. Once the seller's side confirms the funds have arrived, the estate agent is authorised to release the keys and the seller moves out. That is the moment the home is yours and you can move in.

Completion typically happens between late morning and early afternoon, because the money has to clear through the banking system and any chain has to complete in sequence. After the keys are released, your conveyancer still has essential admin to finish, which happens over the following days and weeks rather than on the day itself.

The difference between exchange and completion

The simplest way to hold the two apart: exchange is when you are legally committed to the purchase, and completion is when you actually get the keys and move in. At exchange, nothing physically changes — you cannot enter the property, and the seller still lives there — but you are now bound to go through with it. At completion, the money moves, the ownership transfers, and you take possession. Exchange is the promise; completion is the delivery.

“Think of exchange as signing on the dotted line and completion as the day the transaction is finished. Between the two you are committed but not yet moved in — which is exactly why buildings insurance has to start at exchange, not completion.”

Why is there a gap between exchange and completion?

The gap between exchange and completion is usually one to four weeks, though it can occasionally be the same day. That window exists to give everyone time to make the practical arrangements a binding contract now allows them to commit to: booking removals, arranging the mortgage drawdown, giving notice on rented accommodation, and coordinating everyone in a chain so each purchase can complete on the same day. A fixed completion date the moment you exchange lets the whole chain plan with certainty.

A same-day exchange and completion is possible where there is no chain and both sides are ready, but most buyers prefer a short gap so they can organise the move without racing the clock. Two weeks is a common, comfortable middle ground.

The exchange-to-completion timeline, step by step

• Step 1 — Pre-exchange checks: mortgage offer received, searches clear, enquiries answered, deposit funds cleared with your conveyancer
• Step 2 — Agree the completion date: both sides settle on a date that works for the whole chain
• Step 3 — Exchange contracts: conveyancers swap signed contracts, you pay the ~10% deposit, buildings insurance goes live, the purchase is now binding
• Step 4 — The gap: book removals, confirm mortgage drawdown, give notice on any rental, arrange utilities and address changes
• Step 5 — Completion day: balance of funds transferred, seller's conveyancer confirms receipt, keys released by the estate agent
• Step 6 — After completion: your conveyancer files the SDLT return within 14 days and registers you as owner with HM Land Registry

What can and cannot go wrong

Before exchange, plenty can go wrong: a survey can reveal problems, a mortgage offer can be withdrawn, searches can flag issues, or either party can simply change their mind. This is the fragile phase, and it is why the period before exchange feels the most uncertain. Gazumping — a rival buyer offering more — is only possible before exchange, because until then the seller is not committed to you.

After exchange, the picture is very different. The contract is binding, the completion date is fixed, and neither side can walk away without severe financial penalty. The main remaining risk is a delay on completion day itself — most often a bank transfer arriving late or a chain member completing slowly, which can push the moment you get the keys back by hours. Serious failures after exchange are rare, but if a buyer cannot complete on the agreed date the seller can serve a notice to complete and ultimately keep the deposit.

After completion: what your conveyancer does next

Getting the keys is not quite the end of the legal process. After completion, your conveyancer files your Stamp Duty Land Tax (SDLT) return with HMRC within 14 days of completion and pays any duty owed on your behalf from funds you provided. They then register you as the new legal owner with HM Land Registry, which can take some weeks to finalise. You do not need to chase these steps, but it is worth knowing they are happening in the background before your ownership is formally recorded.

This guide is for informational purposes only and does not constitute financial or legal advice. Conveyancing procedures, deposit arrangements and insurance requirements vary by transaction and by circumstance — always speak to a qualified conveyancer or solicitor before making decisions.