Below 80 years, the freeholder can claim half of the “marriage value”, the extra value a longer lease adds to a flat. On an average London flat, estimated at a market value of £414,000, the premium jumps from around £10,000 with 80 years left to £25,200 with 79. Across England where the average flat is worth £219,000, dropping below 80 years adds around £7,600.
“We regularly speak to leaseholders who had no idea how much a single year could cost them. The 80-year mark is the most important date on your lease, and once it has passed, there’s no going back. The good news is that most of the expensive mistakes we see are avoidable with the right advice at the right time.”
Letting the lease slip below 80 is one of several common mistakes. Others include waiting for leasehold reform that many leaseholders believe will remove the extra cost added to their lease extension due to the proposed removal of marriage value, however these changes are still not definitive (as the new valuation rates have not been agreed or the supporting laws required to achieve this) and will take years to become law in legal practice.
Below, Tabitha explains the mistakes and common misunderstandings The Lease Extension Company sees most often, what each could cost on an average flat, and how to avoid them. Every lease is different, so the figures are a guide rather than a quote.
Lease Extension Mistakes and What They Could Cost You
1. Letting the Lease Fall Below 80 Years: Around £15,200 in London
- The single most expensive date is the day a lease drops below 80 years, even by just one day.
- Below 80, the freeholder can claim half of the “marriage value”, the extra value a longer lease adds to the flat.
- On an average London flat, estimated at £414,000, the premium jumps from £9,985 at 80 years to £25,174 at 79, an extra £15,190. That is 2.5 times as much, for the sake of one year.
- Whilst an average flat in England, valued at £219,000, the premium jumps from £6,059 at 80 years to £13,703 at 79, an extra £7,644.
- Even missing the 80-year mark by a single month adds £7,043 on an average flat in England, because marriage value applies from the day the lease drops below 80.
- In London, slipping below 80 costs almost four times as much as in the North East, where it adds £3,973.
The notice that doesn’t stop the clock
One of the costliest ways to miss the 80-year mark is believing you’ve already beaten it. A Section 42 notice is the formal notice that starts a statutory lease extension, and serving a valid one fixes the date the premium is valued at, effectively stopping the clock.
If the notice is invalid, the clock never stopped. Invalid notices usually happen when leaseholders serve the notice themselves, or use a conveyancer or solicitor who doesn’t specialise in this niche area of law. By the time the problem comes to light, the lease may already be below 80 years, and the leaseholder may have to wait 12 months before serving a new notice.
“We often hear from leaseholders who served a notice themselves, thinking they had locked in the price before the 80-year deadline, only to find it wasn’t valid. By then it’s usually too late. Using a lease extension specialist to prepare and serve the notice is the simplest way to avoid it.”
2. Waiting for Reform: A Gamble That Could Cost You More
Many leaseholders near the 80-year mark are holding off in the hope that marriage value will be abolished. But nothing is certain yet.
- Proposed, not in force. The abolition of marriage value and 990-year lease extensions have been proposed in law, but are not yet in legal practice. The replacement valuation rates have not been determined, and no implementation date has been set.
- At least two more years. The changes needed to the existing 2024 Act, and the review and introduction of the Commonhold and Leasehold Reform Bill, are likely to take a minimum of two further years to implement. The Bill has not yet been introduced to Parliament, which is the first step in the legislative process. It must pass through both the House of Commons and the House of Lords before receiving Royal Assent and becoming law. This process typically takes 9–12 months, although timings can vary. Further steps may then be needed before its provisions come into force.
- Nothing has changed for now. Lease extensions continue as normal under the Leasehold Reform, Housing and Urban Development Act 1993, and marriage value still applies below 80 years.
Freeholders are fighting the reforms in court
Six groups of freeholders have taken the Government to court, arguing that parts of the 2024 Act, including scrapping marriage value and changing who pays costs, breach their human rights. The High Court dismissed their claims in October 2025, but permission to appeal was granted in April 2026. If the freeholders are unsuccessful after exhausting UK appeal routes, they could take their case to the European Court of Human Rights.
For leaseholders, this matters in two ways. It could delay the reforms even further. And it puts pressure on the Government to set the new valuation rates carefully: if they don’t reflect market value, they could face a fresh legal challenge.
What waiting could cost
In the meantime, the lease keeps getting shorter, and the premium keeps rising.
- On an average London flat: extending with 78 years left costs around £26,400. Wait three years for reform that doesn’t arrive, and extending at 75 years costs around £30,200, an extra £3,800. Wait eight years, until 70, and it costs around £37,600, an extra £11,200.
- On an average flat in England: the premium rises from around £14,400 at 78 years to £16,400 at 75, an extra £2,000, and £20,300 at 70, an extra £5,900.
3. Waiting Too Long: £25,400 Extra Over 10 Years in London
- On an average London flat: going from 85 to 81 years adds around £1,400. But wait 10 years, from 82 to 72, and the premium rises from around £9,200 to £34,600, an extra £25,400. If flat prices rise by 2% a year, the extra cost climbs to around £32,800.
- On an average flat in England: going from 85 to 81 years adds £741. Waiting from 82 to 72 years raises the premium from around £5,700 to £18,700, an extra £13,000, or around £17,000 if flat prices rise by 2% a year.
4. Keeping Your Ground Rent in an Informal Deal: £43,750 Over 75 Years
A statutory lease extension has two big advantages. It reduces the ground rent to a peppercorn, effectively zero. And once the Section 42 notice has been served, the whole process is protected by law: the freeholder must respond within set deadlines, and if you can’t agree terms, a tribunal can decide them. Informal deals offered by freeholders often keep the existing ground rent. They can also include terms that favour the freeholder, offered on a “take it or leave it” basis.
Example: an informal offer keeps a £250 ground rent that doubles every 25 years. Over the remaining 75 years, it rises to £500 and then £1,000 a year, adding up to £43,750 in total. Even in today’s money, that’s worth around £5,400, a cost the statutory route avoids entirely.
- Even a fixed rent adds up: £100 a year over 75 years comes to £7,500.
5. Skipping Your Own Valuation: £4,105 on a 70-Year Lease
The premium depends on a few technical assumptions that valuers can reasonably disagree on. Accept the freeholder’s figure without your own valuation, and small shifts in those assumptions can cost you thousands.
- On an average London flat: with 70 years left, the premium is around £37,600. Three small changes push it to around £45,200, an extra £7,630.
- On an average flat in England: the premium is around £20,300. The same changes push it to around £24,400, an extra £4,105.
The three changes are:
- Relativity (the value of your current lease compared with owning the flat outright) 3 percentage points lower: +£6,273 in London, +£3,318 in England
- Deferment rate (used to value the freeholder’s right to get the flat back) 4.75% instead of 5%: +£1,209 in London, +£639 in England
- Capitalisation rate (used to value the ground rent) 5% instead of 6%: +£148 in both
6. Missing a Statutory Deadline: Around £2,600
Once a Section 42 notice has been served, the process runs to strict legal deadlines. After the freeholder responds with a counter-notice, both sides have six months to agree terms. Most claims settle within that time, and going to tribunal should rarely be needed. But if terms aren’t agreed and the deadline passes without action, the claim is treated as withdrawn. The leaseholder then has to pay the freeholder’s costs and wait 12 months before starting again.
- On an average London flat: with 75 years left, that means paying the freeholder’s costs and restarting at 74 years, adding around £3,200, plus wasted fees and the cost of new fees to restart the process
- On an average flat in England: the same mistake adds around £2,600, plus wasted fees and the cost of new fees to restart the process
The good news is that this is easily avoided. With a specialist lease extension solicitor, tracking and meeting every deadline is their responsibility, not yours.
7. Budgeting Only for the Premium
The premium isn’t the only cost of extending a lease. Under the statutory route, leaseholders pay their own valuer and solicitor, and the freeholder’s reasonable costs too.
“One of the most common surprises we see is leaseholders who budget only for the premium, then find there are professional fees on both sides to cover as well. Ask for a clear, upfront quote that covers your own costs and what you’re likely to pay towards the freeholder’s, so there are no surprises halfway through the process.”
Selling or Remortgaging? Check Your Lease First
A short lease doesn’t just cost more to extend. It can make a flat harder to sell or remortgage.
- Lease length: many mortgage lenders want at least 89 years left on a lease, and most won’t lend below 70.
- Value: a flat with 70 years left could be worth around 12% less than one with a long lease. On an average London flat, that’s about £49,700. On an average flat in England, it’s about £26,280.
- Ground rent: some lenders turn down flats where the ground rent is more than 0.1% of the property’s value. On an average London flat, a £250 rent is 0.06%, under that line, but after its first doubling it reaches 0.12%, over it. On an average flat in England, the same rent is already over the line at 0.11%, rising to 0.23% after its first doubling.
The 89-year mark matters twice. It’s the minimum many lenders look for, and extending is still relatively cheap at that point: around £7,000 on an average London flat and £4,500 on an average flat in England.
How to Avoid Them
- Start before 89 years. Our analysis shows the average premium at 89 years is around £7,000 on a London flat and £4,500 in England.
- Never let the lease drop below 80 years. It is the most expensive year you can lose.
- Don’t risk serving the notice yourself. Use a lease extension specialist so the Section 42 notice is valid first time.
- Understand the cost of waiting for reform. The abolition of marriage value is proposed, not in force. If you’re near 80 years, get advice on whether waiting really pays.
- Use the statutory route where you can. It adds 90 years and cuts ground rent to a peppercorn.
- Read any informal offer closely. Check the length of the new lease and what happens to the ground rent, and understand the pitfalls of agreeing terms informally with your freeholder.
- Get your own valuation from a specialist ALEP and RICS surveyor. A few percentage points on the assumptions can mean thousands of pounds.
- Use a specialist ALEP enfranchisement solicitor. They will track every statutory deadline, so your extension goes through without extra legal costs or a year’s delay.
- Budget for both sides’ fees. The premium isn’t the only cost: you’ll also pay your own and the freeholder’s professional fees. A fixed-fee service means you know exactly what you’ll pay from the start.
- Check your lease before you sell or remortgage. Many lenders want 89 years or more.
How we help leaseholders avoid these mistakes
At The Lease Extension Company, we work with a curated panel of specialist ALEP solicitors and RICS surveyors, with our own team overseeing every case from start to finish:
- Your Section 42 notice is prepared and served correctly, so the clock is stopped from day one.
- Every statutory deadline is tracked for you, so nothing is missed.
- You get an independent valuation, so you don’t simply accept the freeholder’s figure.
- Our fixed fees mean you know your costs upfront, with no surprises along the way.
“Most of the mistakes in this guide come down to timing or not having the right advice. Our job is to take that worry away, so leaseholders can extend their lease with confidence and without paying more than they need to.”
Methodology
These are illustrative calculations by The Lease Extension Company, not valuations of specific properties. Unless otherwise stated, the examples use an England flat value of £219,000, based on HM Land Registry’s June 2026 UK House Price Index, and £100 annual ground rent.
Regional flat values, including London’s £414,000, are estimates: each region’s average price for all property types in the same release, multiplied by England’s ratio of flat prices to all property prices (0.75).
Premiums follow the statutory method under the Leasehold Reform, Housing and Urban Development Act 1993. Below 80 years, the premium includes the freeholder’s 50% share of marriage value. Our model uses a 5% deferment rate, the tribunal benchmark for flats set in Cadogan v Sportelli, a 6% capitalisation rate, and an average of the Gerald Eve 2016 and Savills 2015 relativity graphs. These inputs are modelling assumptions, not a guarantee of the rates that would apply to a particular claim.
Property values are held constant unless a growth scenario is specified. Future ground rent totals are undiscounted. Figures exclude VAT and stamp duty.
Disclaimer
This article is for general information only and does not constitute legal, financial or valuation advice. The figures are illustrative examples based on average flat values and modelling assumptions, not valuations of any specific property. Every lease is different, and the cost of extending will depend on your lease terms, property value, location and individual circumstances. Leasehold law and the proposed reforms may change. You should seek independent professional advice on your own situation before taking any action.
