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Guide for developers

Why new build sales fall through, and how developers stop it

Most failed sales don't collapse overnight. They drift for weeks while everyone assumes someone else is on it. Here's where new build sales go wrong between reservation and completion, and what you can do about each one.

By PlotBot, built by new homes salespeople8 minute readUpdated 22 October 2026

The short version

  • About 1 in 3 agreed UK property sales fall through within a year, and nearly half of those fall through after the first 90 days.
  • New build carries risks resale doesn't: the build itself, long gaps between exchange and completion, and incentives that lenders need to see.
  • Most fall-throughs give warning signs weeks earlier. The fix is knowing, every day, who each sale is waiting on, and acting the same week.

Where in the sale it goes wrong

A new build sale has more stages than a resale, and a longer gap between them. Each stage has its own way of failing.

  1. Reservation
  2. Sales memo
  3. Contracts issued
  4. Exchange
  5. Build and sign-off
  6. Notice to complete
  7. Completion
Before exchangeLegal work stalls, the valuation comes in low, or the mortgage isn't placed.
Between exchange and completionThe build runs late and the buyer's mortgage offer runs out.
At noticeThe buyer isn't ready to complete in the time the contract allows.

Seven reasons new build sales fall through

1. Legal work stalls before exchange

Contracts go out, then searches, enquiries and missing documents pile up. Weeks pass with nobody owning the next step, and the buyer starts to wonder whether the sale is real.

What you can do
  • Send a complete contract pack on the day contracts are issued: title, planning, warranty details and, for leasehold, the management pack.
  • Set an expected exchange window for every sale from the day contracts go out.
  • Know who each sale is waiting on, and chase the same week, not the same month.

It makes a real difference. Half our own sales exchange within 7 weeks of contracts being issued, against about 4 months for the average UK sale.

From the sales floor

Before we built PlotBot, we had a sale where the buyer's solicitor couldn't move on until they had an estimated completion date. The request had been sitting with the developer's own solicitor for nearly a week, and it was never passed on, so the developer had no idea anyone was waiting. All it needed was for the developer to be told. A week was lost on a question that was sitting in the wrong inbox.

It's the kind of hold-up we built PlotBot to show: every open request, who it's waiting on, and for how long.

2. The mortgage offer expires before completion

Most mortgage offers last around six months. Some lenders give new build longer, or extend an offer on request. But if the build runs late, the offer can run out before notice is served, and the buyer has to reapply, sometimes on worse terms or not at all.

What you can do
  • Track each buyer's offer expiry date against your expected handover date.
  • Flag any sale where the gap is closing, and tell the agent and the broker early, so an extension can be requested in time.
  • Give realistic handover dates from the start, and update them the moment they move.
From the sales floor

Before we built PlotBot, one of our sales hit exactly this. The build ran late, and the buyer's mortgage offer was heading for expiry before completion. We only knew because we were tracking both by hand: calling the developer for build progress, and checking the offer expiry with the broker. Getting the offer extended took more calls and emails to the broker. We got it done, but it was hard work.

It's what we built PlotBot to do: track build and handover dates against each buyer's mortgage offer, and flag the sale as soon as the gap starts to close.

3. The valuation comes in low

A down valuation leaves the buyer short of the agreed price. They have to find the difference, renegotiate, or walk away.

What you can do
  • Price against recent local new build sales, not just your appraisal.
  • Disclose incentives properly on the UK Finance Disclosure of Incentives Form, so the valuer and the lender aren't surprised.
  • Have your comparable evidence ready before the valuer visits.

4. Lender restrictions on the property

Some lenders limit lending on flats, or won't lend on certain lease terms, warranties or service charge arrangements. A case placed with the wrong lender loses weeks.

What you can do
  • Have the lease terms, warranty provider and charges ready for every plot, so brokers can place the case with the right lender first time.

5. The buyer isn't ready at notice

Notice to complete usually gives the buyer around 10 working days, as set by the contract. If the mortgage offer has lapsed or the funds aren't in place, completion slips and everyone waits.

What you can do
  • Check readiness before you serve notice: contracts signed, a valid mortgage offer or cash in place, and the buyer's solicitor ready.

6. Dates move and nobody explains why

Handover moves, nobody says why, and the buyer hears it second-hand. Confidence drops, and a nervous buyer is the one most likely to walk.

What you can do
  • Give every moved date a reason, and tell everyone involved on the same day, through the agent.

7. Circumstances change during a long wait

Off-plan buyers can wait a year or more. Jobs, interest rates and plans change in that time.

What you can do
  • Keep the sale warm through the agent, with regular build updates.
  • Keep reservation and exchange timescales realistic, so a buyer isn't committed for longer than they expected.

What drift costs a developer

A sale that drifts doesn't just risk falling through. It delays the money you're relying on.

£37,500
EVERY MONTH OF DELAY

That's the interest on a £5m development loan at 0.75% a month, a typical rate for UK development finance. Every month a sale drifts adds to that bill, and that's before a sale falls through and the plot has to be sold again.

Illustration. Typical development finance rates of around 0.55% to 0.85% a month (Funding Agent, August 2026; Funding 365, September 2026). Your rate and loan will differ.

A fall-through checklist for developers

Where PlotBot fits

We built PlotBot because we spent 20 years doing this by hand.

PlotBot puts every sale on one live record, with a red, amber or green status and a plain answer to "who are we waiting on?". It sends automatic reminders to whoever that is, tracks handover against each buyer's mortgage offer expiry, checks readiness before notice, and forecasts exchange and completion month by month. It never contacts your buyers: sales are progressed through the agent, the buyer's solicitor and their broker.

See PlotBot for developersRegister interest

Questions developers ask

How common are fall-throughs?

About 1 in 3 agreed UK property sales fall through within a year, and nearly half of those happen after the first 90 days. New build has its own extra risks, mainly build delays against mortgage offers.

How long does a mortgage offer last on a new build?

Usually around six months. Some lenders give new build longer, or extend on request, often subject to fresh checks. The buyer's broker should confirm the exact terms in writing.

How long does a buyer have to complete after notice?

Usually around 10 working days, but it's set by the contract, so check each one.

Can a buyer get their reservation fee back?

Under the New Homes Quality Code, reservation agreements include a cooling-off period of at least 14 days, with a full refund if the buyer cancels in that time. After that, the reservation agreement sets out what can be deducted. Check the current Code and your own reservation agreement.

Sources

This guide is general information, not legal or financial advice.

Also read: Notice to complete on a new build: what developers need to get right