Lease Extension Calculator UK 2026
Estimate the premium for extending your lease to 990 years
Below 80 years triggers marriage value
Why Lease Extension Matters
Extending your lease is one of the most important decisions for leasehold property owners. As your lease decreases, the value of your property typically drops, and the cost of extension increases significantly once you pass the 80-year threshold.
The 80-Year Rule: Once your lease has fewer than 80 years remaining, you must pay "marriage value" to your freeholder. This is typically 50% of the increase in your property's value that would result from extending the lease. This can add tens of thousands of pounds to the cost of extension.
New Leasehold Reform Act: Recent changes have made it easier and cheaper to extend leases. The new regulations cap ground rent at zero for new leases and provide more transparent pricing. However, if you already own a leasehold, acting before your lease drops below 80 years remains crucial.
How to Negotiate: Get a professional valuation, check your lease terms, and consider using a solicitor specialising in leasehold matters. You have the right to a formal valuation from the freeholder once you serve a Notice of Claim.
Frequently Asked Questions
What is the 80-year rule for lease extensions?
Once your lease falls below 80 years, you must pay 'marriage value' - 50% of the increase in property value attributable to the lease extension. This can add thousands to the cost, making it crucial to extend before reaching this threshold.
How much does a 990-year lease extension cost?
The premium depends on the difference between the property's value with a long lease versus its current value, ground rent, and whether marriage value applies. Our calculator provides an estimate based on standard valuation formulas.
Can I extend my leasehold property?
Yes, under the Leasehold Reform Act 1967 (as amended) and the Commonhold and Leasehold Reform Act 2002, you have the right to extend your lease if you own a flat with a lease of over 21 years. Houses have different rights.
What is marriage value in lease extensions?
Marriage value is the additional value created by combining the leasehold interest with the freehold. When you extend the lease, you share this value with the freeholder, typically paying 50% of the increase in property value once the lease drops below 80 years.
Want comprehensive property data? Try a free SIFTPROP due diligence report — instant EPC, flood risk, planning data and value-add analysis.
Try Free Report