Most London property shown to buyers in Dubai and Riyadh is off-plan: a tower that will complete in two or three years, sold from a marketing suite with a 10% deposit. Most London property bought by Londoners is completed: a flat or house that exists, can be walked through, and changes hands in eight to twelve weeks. Both are legitimate; they suit different buyers. The new-build premium is where buyers go wrong.
Buying from abroad
Off-plan or completed? Choosing between a new London tower and an existing flat
How an off-plan purchase works
Off-plan suits a buyer who wants a new home in a new building for the family’s own use, paid for over the build with a 10% deposit and staged payments. A completed flat suits a buyer who wants a rented asset at a fair price, with income from the first month and a yield on real numbers. The catch with off-plan: a new-build premium of 10% to 20% that is partly lost on first resale, service charges of £8 to £12 per square foot, and completion at the contract price whatever the market does.
You reserve a unit from a plan for a fee of a few thousand pounds, exchange contracts within about a month paying a deposit of 10%, often with further staged payments of 5% or 10% at anniversaries, and complete when the building is finished, paying the balance. Between exchange and completion the developer builds; you are bound to buy at the agreed price whatever the market does. Stamp duty is paid on completion, on the full price. The deposit should be held by the developer’s solicitor or protected by a warranty-backed scheme; check which, because an unprotected deposit is a loan to a company you have not investigated.
How buying a completed London flat works
You find a flat that exists, agree a price, instruct a solicitor and a surveyor, exchange with a 10% deposit when the searches and survey are done, and complete a week or two later. The whole thing takes two to three months, the price is tested against what the same flat let for last year, and the rent starts the month after completion. Our guide to the buying process sets out each step for an overseas buyer.
The advantages of buying a London flat off-plan
What the sales suite is right about:
- A new building: warranties, modern services, a concierge and amenities, and no refurbishment for a decade.
- Spread payments: payment spread over the build, which suits a buyer accumulating funds.
- Price and choice: a price that may be below the completed value if the market rises during the build, and a choice of the best units early.
- A simpler purchase: no chain, no survey of an existing structure, and a developer used to overseas buyers and powers of attorney.
The costs and risks of buying a London flat off-plan
What the sales suite leaves out:
- A new-build premium: the price of a new flat typically stands 10% to 20% above a comparable second-hand one, and part of that premium is lost on the first resale.
- Service charges: on amenity-heavy towers they can run to £8 to £12 per square foot a year, against £3 to £6 for a plain period conversion, and they come straight off the rent.
- Market risk during the build: if values fall, you still complete at the contract price, and a lender’s valuation at completion may come in below it.
- Delivery risk: delays are common, and a developer that fails leaves buyers as unsecured creditors unless the deposit was protected.
- A completion cluster: when a tower of 300 flats completes, 300 landlords look for tenants in the same month, and rents in the building soften for a year.
The advantages of buying a completed London flat
What an existing flat gives the buyer:
- Evidence: the building’s service charge history, the rent the last tenant paid, the condition of the roof, the state of the lease, the neighbours.
- Income now: income from the first month, and a yield worked out on real numbers rather than a brochure.
- A wider market: period houses, mansion blocks and conversions in the established districts, which off-plan cannot supply.
- Negotiation: the ability to negotiate on price against the facts, which is harder in a sales suite with a price list.
The costs of buying a completed London flat
What the completed route asks of the buyer:
- Money up front: the full price within three months, and the stamp duty with it.
- A survey and, on an older building, the possibility of works: a lift, a roof, cladding remediation on a 2000s block.
- More searching: more work in finding the right one, since completed flats are sold one at a time, by hundreds of agents.
Questions that decide between off-plan and completed property
Do you want income now, or in three years? Is the money ready, or being gathered? Will you or your family use the property, in which case the district, the building and the view matter more than the yield? Are you buying one flat, or building a holding?
Which route suits which buyer: off-plan or completed flat
A buyer who wants a rented asset at a fair price in a district with a track record will usually do better with a completed flat chosen on the evidence. A buyer who wants a new home in a new building for the family’s own use, paid for over time, is the buyer off-plan was designed for. We act for both, and in either case the decision is made on the lease, the service charge and the comparable sales rather than the brochure.
Related guides: Battersea and Nine Elms, Manchester city centre and Due diligence on a London property when you live abroad.
Sources: Building Safety Act 2022 (legislation.gov.uk) · NHBC. Figures are indicative of the London market at that date and vary by district and building. General information, not advice on a particular purchase. Figures verified 13 October 2026.
Frequently Asked
Questions about off-plan or completed London property
Ten to twenty per cent on exchange, sometimes staged higher; if the developer fails before completion the deposit is protected only to the extent the contract and any warranty scheme provide, which varies.
Yes: fifteen to twenty-five per cent over a comparable flat in a ten-year-old block in the same district, and the resale market has not consistently paid it back.
The developer’s completed record, the warranty provider, the service charge estimate, the build safety status and the completion date clause; our due diligence guide lists the questions.
You reserve a unit from a plan for a fee of a few thousand pounds, exchange contracts within about a month paying a deposit of 10%, often with further staged payments of 5% or 10% at anniversaries, and complete when the building is finished, paying the balance. You are bound to buy at the agreed price whatever the market does. Stamp duty is paid on completion, on the full price.
Two to three months. You find a flat that exists, agree a price, instruct a solicitor and a surveyor, exchange with a 10% deposit when the searches and survey are done, and complete a week or two later. The price is tested against what the same flat let for last year, and the rent starts the month after completion.
On amenity-heavy towers they can run to £8 to £12 per square foot a year, against £3 to £6 for a plain period conversion, and they come straight off the rent. A completed flat lets you read the building’s service charge history before you buy; off-plan you have the developer’s estimate.
You still complete at the contract price, and a lender’s valuation at completion may come in below it, leaving you to fund the gap. Delays are also common, and a developer that fails leaves buyers as unsecured creditors unless the deposit was protected.
Not immediately. When a tower of 300 flats completes, 300 landlords look for tenants in the same month, and rents in the building soften for a year. A completed flat in an established building has income from the first month, with a yield worked out on real numbers rather than a brochure.
By the developer’s solicitor, or protected by a warranty-backed scheme. Check which before exchange, because an unprotected deposit is a loan to a company you have not investigated, and if the developer fails you rank as an unsecured creditor.
Ask whether you want income now or in three years, whether the money is ready or being gathered, and whether the family will use the property. A buyer who wants a rented asset at a fair price in a district with a track record usually does better with a completed flat chosen on the evidence. A buyer who wants a new family home, paid for over time, is who off-plan was designed for.
