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A standard mortgage offer lasts around six months. New build homes routinely take longer than that from reservation to completion, and build dates slip. When the offer expires before the home is finished you need either an extension or a new offer, and both involve the lender looking at you again. Rates may have moved, your circumstances may have changed, and the lender’s criteria may have changed too. This is the single most common problem I deal with on new build purchases, and most of it can be planned for before you exchange.
How long mortgage offers last
Most lenders issue offers valid for six months from the offer date, though some use three months and a few longer. Several lenders have specific new build policies: some issue new build offers valid for nine months from the start, some allow a formal extension of a few weeks or months on request, and a small number will extend further with a fresh review. One large lender, for example, now issues new build offers valid for 270 days with no further extension, having previously offered 180 days plus a 45 day extension. The policies differ a lot, so when the developer’s completion date is uncertain, choosing a lender with a long offer period is one of the first decisions I make.
Standard offers last about six months; some lenders give nine months or more on new build.
An extension or re-offer means the lender re-checks your income, credit and sometimes the valuation, at current rates.
Pick the lender for its offer period as well as its rate when the completion date is uncertain.
Why new build dates slip
Building a house involves dozens of trades, materials deliveries, utility connections and inspections, and any one of them can push completion back. Developers give an anticipated completion window rather than a date, and long stop dates in the contract are often many months after the expected one. Industry reporting suggests a majority of new build purchases see some delay. That does not mean panic; it means the mortgage needs to be arranged with delay in mind rather than assuming the first date holds.
What an extension involves
If your lender allows an extension, you usually apply in the last few weeks before expiry. Some lenders grant a short extension on a simple confirmation that nothing has changed. Others treat it as a new application: updated payslips or accounts, a new credit search, a fresh affordability assessment and sometimes a new valuation. If you pass, the offer is extended on the same product in most cases. If you have changed jobs, taken on new credit, had a child, or your income has fallen, the extension can be declined even though the original offer was fine. The lender is not being difficult; its offer was a commitment based on the position at the time, and the position has moved.
What a re-offer involves
If the lender does not extend, or you have gone past the extended date, you need a new mortgage offer, either from the same lender or from another. That is a full new application at today’s products and rates. If rates have risen since your original offer, your monthly payment rises with them, and I have seen that cost buyers a meaningful amount a month on the same house. If rates have fallen you may do better. Either way, the valuation may be repeated, and on a new build a repeat valuation carries its own risk, which I cover in my guide to new build down valuations.
Protecting yourself before exchange
Three things. First, choose a lender whose offer period comfortably covers the developer’s anticipated completion window, plus a margin. Second, read the contract’s long stop date: this is the last date the developer must complete by before you can withdraw, and if it is far beyond your offer period you are carrying the risk of a re-offer. Your solicitor can sometimes negotiate this. Third, keep your finances steady between offer and completion: no new credit, no job changes if you can avoid them, and tell me straight away if anything does change, so we can plan rather than react. My new build mortgages page covers the wider process.
Speak to an expert
Completion date moved and your offer is running out? Tell me the lender, the offer date and the new completion window and I will tell you today whether an extension is available or what a re-offer looks like.
What if you cannot get a new offer?
If your circumstances have changed and no lender will re-offer at the level you need, the options are a larger deposit, a lower loan from a different lender, family help through a guarantor or JBSP mortgage, or in the worst case withdrawing from the purchase. Withdrawing after exchange means losing your exchange deposit and potentially facing a claim from the developer, which is why the offer period question needs settling before exchange, not after.
Incentives and extensions
If your purchase relied on a scheme or incentive that no longer exists at the point of re-offer, such as Deposit Unlock, which closed to new completions in April 2026, the replacement mortgage has to work without it. I have written about the options in my guide to what to do now Deposit Unlock has closed.
The short version
Plan for delay from the start by choosing the lender partly for its offer period, know your long stop date, keep your finances steady, and get in touch the moment a delay looks likely rather than the week the offer expires. Whether an extension or a re-offer is the better route, and with which lender, depends on your position at the time, which is what an advice appointment is for. Call me on 01425 203055 or book a 15 minute call.
Need Personal Mortgage Advice?
Every buyer’s situation is different. While this guide explains the general rules, the right mortgage for you depends on your income, deposit, credit history and future plans. If you’d like tailored advice, I’m here to help, with whole-of-market coverage.
