Leasehold Extension Cost Calculator UK 2025/26
Extending a leasehold flat's lease is one of the most important financial decisions a UK flat owner can make. A short lease dramatically reduces a flat's value and mortgage availability, while a long lease (90+ years remaining) generally has minimal impact on value or saleability. The cost of extending escalates significantly as the lease gets shorter — particularly once it falls below 80 years, at which point marriage value becomes payable, adding substantially to the statutory premium.
This calculator provides a realistic estimate of the extension premium range based on your remaining lease length as a proportion of flat value, together with the professional fees that form the total cost of the process. The estimate uses widely-accepted percentage bands used by leasehold specialists for preliminary planning purposes. For a precise figure, you need a RICS-accredited leasehold valuation surveyor to produce a formal opinion.
The Leasehold and Freehold Reform Act 2024 introduces important changes including moving to 990-year extension terms and the eventual removal of marriage value — which will reduce costs for short-lease holders. Some provisions require separate commencement orders.
Key Leasehold Extension Facts 2025/26
- Statutory right to extend by 90 years (or 990 years under new rules once commenced)
- Must own flat for at least 2 years to exercise statutory right
- Ground rent reduced to peppercorn (zero) after extension
- Marriage value applies for leases below 80 years — act before reaching this threshold
- You pay the landlord's reasonable legal and valuation costs as well as your own
- Typical total cost: £3,000 – £25,000+ depending on lease length and flat value
Leasehold Extension Cost Estimator
Enter your lease details to estimate the extension premium and total costs. Note: for a precise premium you need a specialist RICS surveyor valuation.
Premium estimates use lease-length percentage ranges applied to flat value. Actual premiums vary significantly by location, freeholder, ground rent, and are best determined by a RICS-accredited leasehold specialist.
Lease Extension Premium Guide by Lease Length
| Remaining Lease | Est. Premium (% of Flat Value) | Marriage Value | Priority Level |
|---|---|---|---|
| >80 years | 1% – 5% | None | Low — monitor |
| 70–80 years | 5% – 8% | Low-moderate | Medium — plan now |
| 60–70 years | 8% – 15% | Moderate | High — act soon |
| 50–60 years | 15% – 25% | Significant | Urgent |
| <50 years | 25% – 40%+ | Very high | Critical — act immediately |
The Marriage Value Explained
Marriage value is the additional value created when a short lease is extended. When a flat has a lease of, say, 55 years, it is worth less than an identical flat with a 150-year lease. The difference in value is partly attributable to the enhancement brought about by the extension. Under current statutory rules, when the lease is below 80 years, the freeholder is entitled to 50% of this marriage value as part of the premium.
Example: a flat worth £300,000 with a 65-year lease might be worth £340,000 with a 155-year lease after extension. The marriage value is £40,000, and 50% (£20,000) is added to the premium. This is on top of the ground rent capitalisation and reversion value components. The closer the lease is to expiry, the larger this marriage value component becomes.
This is why the 80-year rule is so significant. If your lease is at 85 years, extending immediately avoids marriage value entirely and typically costs 2–5% of flat value. Waiting until it drops to 75 years could add tens of thousands to the premium for the same flat.
Statutory vs Informal Extension
The statutory route gives you legal protection, prescribed timescales, and the right to take the matter to tribunal if you cannot agree a price. The informal route is negotiated directly with the freeholder without using the legal framework, which means the freeholder can set whatever terms they like including continued ground rent, different extension periods, or refusal to negotiate at all.
For leases above 80 years where the freeholder is cooperative, an informal approach can be faster and sometimes cheaper. For shorter leases where premium negotiation is material, using the statutory route protects you from an unreasonably high informal offer and ensures your rights are preserved throughout the process. Any informal offer received should be checked against a surveyor's statutory valuation before agreeing.
Frequently Asked Questions
1. Do I have a legal right to extend my lease?
Yes, most flat owners in England and Wales have a statutory right to extend their lease by 90 years on top of the remaining term, with the ground rent reduced to a peppercorn (zero). To exercise this right, you must have owned the flat for at least two years. The right is governed by the Leasehold Reform Housing and Urban Development Act 1993 and the Leasehold and Freehold Reform Act 2024.
2. How is the lease extension premium calculated?
The statutory premium has three components: the present value of ground rent lost by the landlord; the present value of the reversion (getting the property back at the end of the extended lease); and marriage value — which is 50% of the increase in flat value resulting from the extension. Marriage value only applies when the lease is below 80 years. This makes extending a lease approaching 80 years particularly urgent.
3. Why is 80 years such an important threshold?
When a lease drops below 80 years, marriage value becomes payable as part of the premium. Marriage value is 50% of the increase in the flat's value attributable to the lease extension. For a flat where the extension adds £30,000 of value, this would add £15,000 to the premium. Extending before the lease drops to 80 years avoids this additional cost entirely.
4. What are the typical professional fees for a lease extension?
You will typically pay: your own solicitor £1,500–£4,000; your own surveyor (to value the premium) £500–£1,500; the landlord's solicitor fees £750–£2,000; and the landlord's surveyor fees £500–£1,500 (these are payable by you as the tenant under the legislation). Total professional fees typically range from £3,250 to £9,000 depending on complexity.
5. How long does a statutory lease extension take?
A straightforward lease extension where both parties agree quickly can complete in 3–6 months. Contested cases where the premium is disputed can take 12–24 months or more, sometimes proceeding to the First-tier Tribunal (Property Chamber) for a determination. Serving the formal Section 42 Notice initiates the statutory timetable. The landlord has 2 months to serve a Counter Notice.
6. Can I extend informally rather than through the statutory route?
Yes. An informal extension is negotiated directly with the freeholder outside the statutory process. It can be quicker and sometimes cheaper, especially if the freeholder is cooperative. However, an informal extension does not have to reduce ground rent to a peppercorn, can include different terms, and there is no statutory protection. For leases above 80 years, informal negotiation is often worth trying first.
7. Does the Leasehold and Freehold Reform Act 2024 change extension costs?
Yes. The Leasehold and Freehold Reform Act 2024 makes important changes including the removal of marriage value for leases below 80 years (once the relevant provisions are commenced), which will significantly reduce premiums for shorter leases. The new standard extension term is 990 years (replacing the previous 90-year extension). The commencement date for some provisions is still awaited.
8. What happens to ground rent after a lease extension?
Under the statutory route, ground rent is reduced to a peppercorn (effectively zero) for the extended lease. You stop paying ground rent on completion. This can be a significant financial benefit for leaseholders paying high ground rents or leases with escalating ground rent clauses — some of which HMRC and lenders treat as onerous.
9. Can I sell my flat while a lease extension is in progress?
Yes, and the benefit of a pending Section 42 Notice can be assigned to a buyer. This allows a seller to serve the notice, benefiting from the right to extend, and then assign the benefit to the buyer on exchange of contracts. Solicitors regularly handle this in flat sales where the lease is short. The buyer takes over the extension process and pays the premium once agreed.
10. Will my mortgage lender care about my lease length?
Yes. Most UK mortgage lenders require the unexpired lease term at the end of the mortgage to be at least 70–85 years. Many lenders will not lend at all on leases below 70 years. Leases below 80 years can significantly impact resale value and mortgage availability, making early extension a financial priority for leaseholders approaching these thresholds.
11. What if my freeholder is unresponsive or cannot be found?
If the freeholder cannot be found or fails to respond to the Section 42 Notice within the statutory timetable, you can apply to the County Court to execute the lease extension on your behalf. A court-appointed person can execute the deed. If the freeholder cannot be traced, the premium can be paid into court. These scenarios add cost and delay but do not prevent you from obtaining the extension.
12. Can I group with neighbours to extend leases at the same time?
There is no formal group statutory extension process for individual leases, but your solicitor and surveyor can manage multiple extensions with the same freeholder simultaneously, often at lower combined professional cost. If 50% or more of qualifying leaseholders wish to buy the freehold collectively, a different process — collective enfranchisement — may be more advantageous than individual lease extensions.