Lease Extension Premium Calculator 2026
Estimate your lease extension premium using the Relativity method. Extended under the Leasehold Reform (Ground Rent) Act and new 2024 reforms.
Lease Extension Cost Estimator
Frequently Asked Questions
What is a lease extension?
A lease extension increases the remaining term of your leasehold property. Under the Leasehold Reform (Housing & Urban Development) Act 1993, qualifying flat owners can extend by 90 years on top of the existing term at zero ground rent.
What does the 2024 Leasehold Reform Act change?
The Leasehold and Freehold Reform Act 2024 allows leaseholders to extend by 990 years (not just 90), removes ground rent to zero, and makes the process easier. Implementation of some parts is ongoing.
How is the lease extension premium calculated?
The premium is calculated using three components: (1) the capitalised value of ground rent lost by the freeholder; (2) the 'reversion' (value of regaining the freehold at lease expiry); and (3) a share of any 'marriage value' if the lease is below 80 years.
What is marriage value?
When a lease has less than 80 years remaining, extending creates additional value (the difference between the current leasehold value and the freehold value). The freeholder is entitled to 50% of this 'marriage value'.
When should I extend my lease?
Before it drops below 80 years — once below 80 years, marriage value kicks in and the premium rises sharply. Many mortgage lenders also require at least 70-85 years remaining.
How long does a lease extension take?
The formal statutory process typically takes 4–12 months. Start with a Section 42 notice (tenant's notice) instructing a solicitor and RICS surveyor.
Can I negotiate directly with the freeholder?
Yes, an informal extension may be quicker and cheaper, but you lose the legal protection of the statutory route. Any informal deal should still be handled by a leasehold solicitor.
What are the eligibility criteria?
You must have owned the flat for at least 2 years. The original lease must have been granted for over 21 years. The building must be a residential purpose.
Does the lease extension apply to houses too?
Houses can enfranchise (buy the freehold) under the Leasehold Reform Act 1967. The 2024 Act makes this easier and cheaper.
What other costs are involved?
Your own legal and surveying fees (£2,500–£5,000+), freeholder's reasonable legal and surveying costs (typically £2,000–£3,000), and SDLT (nil if under £250,000 combined premium and ground rent element).
Can I sell my flat without extending first?
Yes, but a short lease (under 80 years) will significantly reduce your property's value and make it unmortgageable for many buyers.
What if the freeholder refuses to cooperate?
If the freeholder fails to respond to a Section 42 notice within 2 months, you can apply to the First-tier Tribunal (Property Chamber) to determine the premium.