Quick answer
Standard UK mortgage offers are typically valid for 6 months. Many lenders recognise that new-build completions run longer and offer an extended new build validity — commonly around 9 months, with some allowing a further extension that can take the total window towards 12 months or more, usually subject to a refreshed credit search and confirmation nothing material has changed.
If your offer still lapses before completion, you will need to re-apply — at whatever rate and criteria the lender is offering at that point, not your original terms, and with a fresh valuation. Confirm your specific lender's offer-validity period and extension policy as early as possible if a build looks like it is running behind schedule.
In this guide
Standard offer validity — and new-build extensions
Most mainstream UK lenders issue mortgage offers valid for around 6 months (180 days)from application or issue. For an open-market purchase that is usually plenty of time between offer and completion. Off-plan new-build purchases are a different story: the completion date is set by the developer's build programme, not by you, and it is common for 8, 10 or even 12+ months to pass between exchanging on a plot and the keys being handed over.
Recognising this, many lenders build in extra room for new build specifically, and the exact allowance varies a fair amount between them — which is exactly why it is worth checking before you commit to a lender on a long-build purchase, not after. Based on published lender criteria, examples of the range include:
- Standard (non new-build) offers of around 6 months are the norm across most of the market, sometimes with a short further extension of a few weeks available on request.
- Several lenders extend the new-build validity to around 9 months, with a further extension available on top — in some cases bringing the total window closer to 12 months, subject to a refreshed credit search and reconfirming nothing material has changed.
- A smaller number of lenders offer a new-build validity that is double the standard period from the outset — for example extending a 6-month standard offer to around 12 months for new build, sometimes with a further extension available beyond that on a case-by-case basis.
These figures move as lenders update their policies, and the exact conditions attached to an extension — a new credit search, updated payslips, a refreshed valuation, evidence your circumstances are unchanged — vary by lender. The takeaway is not a single number to rely on; it is that offer-validity length and extension terms are worth asking about explicitly, and comparing between lenders, before you choose who to borrow from on an off-plan purchase.
Our buying a new build guide covers the rest of the new-build purchase process, including incentives and snagging, alongside this offer-timing risk.
What re-application actually means
If your offer lapses before completion, the lender is not obliged to simply reissue the same terms. In practice, re-application typically means:
- Re-underwriting at current rates and criteria. You are re-priced onto whatever that lender — or a different one — is offering at the time, and assessed against their current lending policy, not the one that applied when you first got your offer.
- A new valuation. Most lenders require an updated valuation for a fresh offer, particularly if significant time has passed. On a new-build plot this can also mean waiting for the property to reach a stage the valuer is able to assess.
- Possible affordability changes.Your income, outgoings, credit profile or the lender's own stress-test assumptions may all have moved since your original offer. A re-application is assessed against your circumstances now, not the circumstances that supported your original approval — see our guide to how affordability is calculated for what typically changes an outcome.
None of this means a re-application will fail — many complete without incident — but it does mean you should not assume the outcome is guaranteed to match your original offer.
Check your affordability before you commit to a plot
Free 2-minute check across 60+ UK lenders — useful context before choosing a lender for a long off-plan build.
Start My Free CheckDeveloper long-stop dates and your leverage
Your contract with the developer should include a long-stop date — the latest date by which the property must be delivered before you are entitled to walk away without losing your deposit. A common long-stop date is around 12 months after exchange, though this varies by developer and contract, so it is worth checking your specific paperwork rather than assuming a standard figure applies.
The long-stop date is your main protection against an indefinitely delayed build, but it is a backstop, not a day-to-day planning tool. In practice your leverage comes from staying informed: ask the developer about their track record for delivering previous phases on time, request monthly progress updates as completion approaches, and keep your broker briefed so they can act quickly if your mortgage offer is approaching expiry while the build is still not ready.
If the property is eventually down-valued relative to your original purchase price — which can happen if the local market has softened during a long build — see our down-valuation guide for the options at that point.
What to do at 8, 4 and 0 weeks from expiry
- 8 weeks out:ask the developer for a written, realistic completion estimate rather than relying on the original build programme. Ask your broker to confirm your specific lender's extension process and how far in advance you need to request it — some lenders require this 30 days before expiry.
- 4 weeks out: if completion is genuinely not going to happen in time, submit any extension request now rather than waiting, since most lenders need updated documents (payslips, bank statements, sometimes a new credit search) processed before the original offer lapses. If an extension is not available or is not enough, start the conversation about a fresh application in parallel so you are not starting from zero after expiry.
- 0 weeks (expiry has passed or is imminent): confirm in writing with the lender exactly what has happened to your offer, whether a grace period applies, and what a new application would need. At this stage also confirm with your solicitor whether your contractual completion obligations to the developer are affected, particularly if contracts have already been exchanged.
The exchange-deadline trap on off-plan purchases
Off-plan reservations typically come with a deadline of their own — often around 42 days to exchange contracts from reservation, well before the property is finished. Exchanging this early means you are contractually committed to buy at a fixed price before the build is complete, and before you can be certain your mortgage offer will still be valid when completion eventually arrives.
This is the trap: the exchange deadline is driven by the developer's sales process, while the mortgage offer clock is driven by your lender, and the two are not designed to be in sync. The practical safeguard is choosing a lender with a new-build offer window that comfortably covers the developer's stated build timeline, with margin for the kind of delay that is common in construction, rather than one that only just fits the schedule as originally quoted.
For the full walkthrough of reservation, incentives and the rest of the new-build process, our specialist sister site New-Build Mortgage Guide covers new-build purchases in more depth.
Frequently asked questions
Can a mortgage offer be extended?
Often, yes, but it depends on the lender and is not automatic. Many mainstream lenders offer a longer standard validity period for new-build purchases than for open-market ones — commonly 9 months rather than 6 — and some allow a further extension on top of that, sometimes with a refreshed credit search, updated income evidence, or a new valuation. A few will only extend once, and some require you to request the extension a set number of days before the original offer expires. Always confirm the specific extension terms with your lender or broker as soon as a delay looks likely, rather than waiting until the offer has already lapsed.
What if rates rose since my offer?
If your offer expires and you need a new one — from the same lender or a different one — you are generally re-priced at whatever that lender is offering at the time, not at your original rate. Lenders are not obliged to honour an expired offer's terms. This is precisely why offer-validity length matters as much as the headline rate when choosing a lender for an off-plan purchase with a long build programme: a slightly higher rate with a longer, extendable offer window can be worth more than a cheaper rate that lapses before you can complete.
Can I lose my deposit if my offer expires?
A lapsed mortgage offer does not, by itself, take away your reservation or exchange deposit — those are governed by your contract with the developer, not by your lender. The real risk is sequencing: if you have already exchanged contracts with a fixed completion date and your mortgage offer runs out before you can complete, you could be in breach of that contract regardless of the reason, which is where a deposit can genuinely be at risk. This is why it is worth confirming your solicitor and broker are tracking both dates together, particularly on off-plan purchases where the completion date is set by the developer's build programme rather than by you.
Last updated: July 2026
