Extending your lease is one of the most important steps you can take to protect your property’s value and mortgageability. If your lease is under 100 years, its value may already be affected. Once it falls below 80 years, the cost of extending increases significantly due to marriage value.
Our free Lease Extension Calculator gives you an instant estimate of the premium payable under the Leasehold Reform, Housing and Urban Development Act 1993. It’s a quick, useful guide for leaseholders wanting to understand the likely cost of extending their lease before taking formal advice.
To generate your estimate, simply enter:
If you’re not sure about these rates, we recommend leaving them at the default settings. For experienced users, the calculator also allows adjustments to:
The table below shows indicative premiums at three flat values, with the ground rent held constant at £150 per year throughout. Only the unexpired term and the flat value change. These figures are produced by the calculator above, so the two agree.
Read down any column to see the cost of delay. Compare the 81-year and 79-year rows to see the effect of the 80-year threshold.
| Unexpired term | Flat worth £250,000 | Flat worth £500,000 | Flat worth £750,000 | Marriage value |
|---|---|---|---|---|
| 95 years | £5,000 | £7,500 | £10,000 | No |
| 85 years | £6,500 | £10,500 | £14,500 | No |
| 81 years | £7,500 | £12,000 | £17,000 | No |
| 79 years | £16,500 | £31,500 | £46,500 | Yes |
| 70 years | £24,000 | £47,000 | £69,500 | Yes |
| 60 years | £34,500 | £68,000 | £101,500 | Yes |
Assumptions: ground rent £150 per year fixed with no review; capitalisation rate 6%; deferment rate 5%; 90-year extension at a peppercorn rent under the Leasehold Reform, Housing and Urban Development Act 1993. Figures shown are the central estimate; the calculator also produces a low and high figure either side. Premiums exclude the freeholder’s reasonable costs, your own professional fees, Land Registry fees and any SDLT. Illustrative only — your figure will differ.
Once your unexpired term falls below 80 years, marriage value becomes payable and the premium rises sharply.
Marriage value is the increase in the flat’s total value created by the extension itself — the extended lease is worth more than the short lease and the freeholder’s interest were worth separately. Under the 1993 Act that uplift is split equally, and you pay the freeholder half of it.
The effect is not gradual. In the table above, a flat worth £500,000 costs around £12,000 to extend at 81 years and around £31,500 at 79 years. Two years of delay roughly doubles the cost. On a flat worth £750,000 the same two years take the premium from about £17,000 to about £46,500.
The threshold is tested at the date the notice is served, not the date you complete. A lease sitting at 80 years and two months today may be below 80 by the time a claim is prepared and served.
No. As at August 2026, marriage value is still payable on any lease extension completing where the unexpired term is below 80 years.
The Leasehold and Freehold Reform Act 2024 legislates for its abolition, but that provision has not been brought into force. It depends on secondary legislation setting new prescribed valuation rates, and those regulations have not been made. Until they are, lease extensions continue to be valued under the 1993 Act.
| Change | Status | Detail |
|---|---|---|
| Two-year ownership rule abolished | In force | February 2025 |
| Marriage value abolition | Not commenced | Legislated in LAFRA 2024, awaiting secondary legislation |
| New prescribed valuation rates | Not commenced | Consultation opened 15 July 2026 |
| 990-year standard extension term | Not commenced | Legislated, awaiting commencement |
| Ground rent capped in premium calculation | Not commenced | Legislated, awaiting commencement |
| £250 cap on ground rents in existing leases | Draft only | Draft Commonhold and Leasehold Reform Bill |
| Commonhold as default for new flats | Draft only | Draft Bill, not yet law |
A challenge to the abolition brought by freeholders was dismissed by the High Court in October 2025. A corrective Bill is required before the 2024 Act can be commenced, and the draft Commonhold and Leasehold Reform Bill was published in January 2026.
For most leaseholders below 80 years, no. Your lease is depreciating every day, and each year that passes adds to the premium under the law as it currently stands. Commentators widely expect commencement to be at least two years away.
Waiting for a saving that may not arrive before your lease has lost more value than the saving is worth is a poor trade. Whether that applies to you depends on your specific unexpired term, so it is worth taking advice rather than guessing.
Legislative position stated as at August 2026 and reviewed quarterly.
The single biggest driver. Every year that passes increases the premium, and the rate of increase accelerates as the term shortens. Below 80 years it becomes a step change rather than a gradient.
The freeholder loses the income when the lease is extended, so they are compensated for it. A peppercorn or nominal rent adds very little. A rent that doubles every 25 years, or is linked to RPI, can add a substantial sum because the calculation values the whole future income stream.
The premium is calculated by reference to the flat’s value with a long lease. Higher-value flats produce higher premiums for the same unexpired term, as the table above shows.
Two rates do the heavy lifting: the deferment rate, which discounts the freeholder’s future right to get the flat back, and the capitalisation rate, which values the ground rent income. Small movements in either produce large movements in the premium. These are matters of valuation judgement supported by evidence, not fixed figures — which is why two surveyors can reach different numbers on the same flat.
Different calculators apply different deferment and capitalisation rates, and different assumptions about relativity — the relationship between the short-lease value and the long-lease value.
Generic national calculators apply broad assumptions. Ours reflects the evidence we see in London tribunal decisions and settled negotiations. Neither is wrong; they are answering slightly different questions.
Any online estimate is a starting point. The figure that matters is the one supported by evidence when a notice is served, because that is the figure a tribunal would test.
⚠️ Please note:
For any formal purpose, you will need a qualified valuation report prepared by our surveyors.
Our consultants can provide you with a tailored estimate that goes beyond the calculator. By completing the enquiry form on this page, you’ll receive:
Complete the form next to the calculator above and our team at Extension.Lease will provide clear, accurate advice to help you move forward with confidence.
The calculator provides a rough guide only. Lease extension valuations are complex and depend on detailed lease terms, local market evidence, and specialist judgment. Use this tool to get a feel for the likely costs, but always obtain a professional valuation before taking any formal action.
Usually, no but it depends on your specific circumstances. While reforms are expected to simplify the process and reduce costs in the future, marriage value still applies today for leases below 80 years, and premiums rise as time passes. There is no current guarantee that future reform will reduce the price payable. Acting sooner often saves money and protects your property’s value.
Marriage value is an additional cost that applies when a lease has fewer than 80 years remaining. It represents the increase in the flat’s value once the lease is extended, and the freeholder is entitled to 50% of that uplift.
These are technical rates used in lease extension valuations. The capitalisation rate converts the annual ground rent into a present value. The deferment rate is used to calculate the value of the property reverting to the freeholder when the lease ends. Our calculator uses standard defaults unless you choose to adjust them.
No. This tool is for guidance only and should not be used for formal legal or negotiation purposes. For that, you’ll need a qualified valuation prepared by a leasehold reform specialist
The premium depends chiefly on your unexpired term, your ground rent and the value of your flat. Leases above 80 years with a nominal ground rent sit at the lower end. Leases below 80 years attract marriage value and cost substantially more. The worked examples above show indicative figures across a range of terms and values.
Marriage value becomes payable, which typically increases the premium significantly. Marriage value is the uplift created by the extension itself, and under the 1993 Act it is split equally between you and the freeholder. The threshold is tested at the date the notice is served, not the date you complete.
Yes. There is no lower limit on the statutory right. The premium will be higher, and mortgage lenders may already be reluctant to lend on the flat, which is usually a reason to act sooner rather than later.
No. The two-year ownership requirement was abolished in February 2025. You can serve notice once your purchase has been registered at HM Land Registry.
A statutory lease extension needs both: a valuer to determine the premium and negotiate it, and a solicitor to serve the notice and handle the conveyancing. We provide both in one place — RICS-registered valuation by Blakes Chartered Surveyors and the legal work by Arcadia Law.
Yes. The Leasehold and Freehold Reform Act 2024 legislates for its abolition, but that provision has not been commenced and depends on secondary legislation setting new valuation rates. Until those regulations are made, lease extensions continue to be valued under the 1993 Act and marriage value remains payable below 80 years.
