When you buy or sell a home in the UK, one of the most important dates is completion — the official day when the money is sent to the seller, ownership passes to the buyer and the keys change hands. On the face of it, it looks simple: you sign a contract, you agree a date, and that's that. In reality this is often the day that causes the most stress, because it has to be lined up with everyone else in the deal.
Exchange and completion are two different things
These two terms are easy to muddle, so let's start there. A UK property deal has two separate milestones:
- Exchange of contracts — the day the solicitors on both sides swap signed contracts. From that moment the deal becomes legally binding: you can't walk away without losing a great deal. On that day the buyer normally pays the deposit.
- Completion — the later day when the rest of the money actually moves, ownership passes to the buyer, and the keys are handed over.
Put simply: exchange is the promise, completion is the real event.
Completion usually happens 1–4 weeks after exchange. Sometimes the two are set for the same day, but that's riskier — there's far less time to sort out any problems.
Why does this date matter so much?
On completion day a lot of people have to act at once. Here's what hangs on it:
- The lender's release of funds. The buyer's lender has to transfer the mortgage money. Some lenders insist on several working days' notice — set the date too soon and the funds may not arrive in time.
- The solicitors' work. Every document has to be checked, signed and registered. If a permission or certificate is missing, completion is pushed back.
- The seller moving out. The seller has to clear the property in time. If they're buying somewhere themselves, their completion depends on another chain.
- The chain effect. In the UK it's very common for one seller to be buying another home, while their buyer is also waiting on a mortgage or a sale. If one link in the chain falls behind, the whole process grinds to a halt.
- Moving logistics. Removals firms are booked well ahead. If completion slips at the last minute, you can end up paying twice over — or stuck with no help at all.
Your mortgage only covers the price of the home. If your tenancy ends on one day and completion is delayed, you'll be paying for somewhere temporary to stay. People sometimes end up paying twice — for the old rental and the new home at once. Always keep a few days in reserve.
How to choose the right completion date
Weigh up how complex the deal is
If you're buying or selling with no chain, the process is simpler and quicker. Where there is a chain, the date has to suit everyone in it — and that often takes time. For more on why chain-free buyers are so attractive, read our guide to buying chain-free.
Line it up with your lender
Check how much notice your lender needs before it releases the money — usually 5–7 working days. Know that figure before you start agreeing a date.
Talk to the other side
Sometimes a seller is waiting for work on their onward purchase to finish. If you don't know their plans, you can get unpleasant surprises. Keep the lines of communication open.
Plan the move
Friday is the most popular completion day, but that's when removals firms are busiest and most expensive. If you can, choose mid-week: it'll cost less and you'll keep spare working days in hand.
Common mistakes
- An over-optimistic date. An "optimistic" date — say two weeks — gets put forward, but the lender and solicitors simply can't physically keep up.
- Plans that aren't joined up. The buyer books a removals firm in advance, completion is then pushed back, and the result is extra cost.
- Too much pressure. One side tries to force a date that doesn't suit the other at all. That breeds conflict and delay.
- No fallback. If completion is delayed and you've nowhere to stay, you're left scrambling for short-term rental or a hotel.
Practical tips
For the buyer: raise it early — ask your agent to start talking about likely completion timings as soon as the offer is accepted. Have a back-up plan for somewhere to stay for a few days. Build a little budget headroom for possible extra costs. Don't blindly accept a date that doesn't work for you — the deal should suit both sides. Be flexible, but if a delay drags on too long, negotiate compensation.
For the seller: move out on time — the buyer expects an empty home, not an owner still packing. If you're buying somewhere yourself, line up both dates so there's no gap. Check with your solicitor that all the paperwork (EPC, guarantees, plans) is in order well before exchange. If your home is in a chain, accept that everything moves more slowly. For a quick, smooth sale our tips on selling your home fast will also help.
A real-world example
One family set completion for two weeks out, because they needed to move quickly. But the lender couldn't release the mortgage in time. The date slipped another three weeks, and the family ran up roughly £2,000 in extra rent and moving costs. Compare that with a couple in London who had a straightforward chain-free deal: they lined up completion with their lender and solicitors over three weeks, booked the removals firm in good time for a Wednesday — and it all went through smoothly and more cheaply.
A completion date is like an orchestra rehearsal — everyone has to play at the same moment. If one musician comes in late, the whole performance falls apart.
In summary
Completion day isn't just a formality — it's the critical step that decides whether your deal goes through smoothly or turns into a nightmare. It has to be lined up with the lender, the solicitors, the seller, the buyer and even the removals firm. A date set too soon means delays and extra cost; set too late, it can cost you time and money on temporary living. The golden rule: a realistic completion date beats an optimistic one you can't deliver. For more on buying and selling a home, browse our guides.