Leasehold Extension Premium Calculator
Estimate your statutory lease extension premium (1993 Act) and legal/surveyor costs. Models the 80-year marriage value cliff, ground rent capitalisation, and 2024 Reform Act commencement.
Your lease details
✓ Valid UK postcode format
Lease extension premium
Estimated cost to extend your lease by 90 years at peppercorn rent
Enter your lease details below, then tap Calculate premium.
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Before serving a Section 42 notice, ensure your lease extension premium calculation is watertight. Compare verified quotes from RICS-accredited surveyors and specialist leasehold solicitors near you.
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How This Tool Works
This calculator estimates the statutory premium payable to extend a leasehold flat or house under the Leasehold Reform, Housing and Urban Development Act 1993. It models term value, freehold reversion, and marriage value (under 80 years) using First-tier Tribunal capitalisation and Sportelli deferment standards.
- 1Enter your postcode to set regional tribunal rate benchmarks and choose property type.
- 2Input your current short-lease property value and years remaining on the lease.
- 3Enter annual ground rent and review structure (fixed, RPI-linked, or doubling).
- 4The tool calculates the premium breakdown (term, reversion, marriage value) plus RICS and legal fees.
- 5Review the 7-step Section 42 statutory timeline and compare wait-vs-extend economics.
Lease Extension UK — Statutory Valuation, 80-Year Rule & Reform Guide
How premiums are calculated, why the 80-year cliff matters, Section 42 costs, and when to extend under current rules vs waiting for the 2024 Reform Act.
📅 Last updated: August 2026
Quick Tips
Jump-start your understanding with these essential tips
Look at your lease document or Land Registry title — subtract elapsed years from original term. If the unexpired term is under 85 years, plan an extension. If approaching 80 years, act promptly before marriage value triggers.
Marriage value kicks in immediately once your lease drops below 80 years. Serving your Section 42 notice at 80 years and 1 month saves a five-figure sum versus serving at 79 years and 11 months.
Under statutory rules (s.60), you pay the freeholder’s reasonable legal and valuation fees as well as your own RICS surveyor and solicitor costs. Budget £3,500–£6,000 in total professional fees.
A formal RICS valuation establishes a realistic opening offer for your Section 42 notice, preventing costly counter-notice disputes and preserving negotiating leverage.
Step-by-Step Guide
Follow these steps to get the most from this tool
The postcode determines your regional capitalisation and deferment rates — London premiums tend to be higher because freehold values compound faster, while tribunal-accepted rates vary regionally. Prime Central London uses lower rates (higher premiums); regional markets use standard benchmarks.
Enter what your flat is worth today with its current unexpired term. The tool applies standard relativity curves to derive the virtual freehold value and determine whether the 80-year marriage value threshold applies.
Input your current annual ground rent and review terms (fixed, RPI-linked, or doubling). The calculator models the capitalised present value of the landlord's ground rent stream over the remaining term.
The results panel details the how to extend a lease UK cost breakdown, including the premium, legal costs, and RICS lease extension surveyor fees. It displays the value uplift post-extension, net benefit, and the cost of waiting 5 years. If you are close to the 80-year mark, delaying can trigger the expensive marriage-value fee. Even though the Leasehold and Freehold Reform Act 2024 has been signed, the marriage value abolition leasehold 2026 provisions have not yet commenced in practice. Serving a formal Section 42 notice lease extension cost now locks in the current valuation date, protecting you from ongoing market appreciation and the cost of delay.
Advanced Topics
Deep dives for advanced users
When calculating marriage value, the valuer must determine the "relativity" of the current short lease value to its virtual freehold value. Our calculator models the Savills-blended relativity curve, the primary benchmark relied upon in First-tier Tribunal hearings:
| Unexpired Term Remaining | Relativity % (Savills-Blended) | Implied Marriage Value Risk |
|---|---|---|
| 85+ Years | 100.0% (No Marriage Value) | Zero — Standard Reversion & Term Only |
| 79 Years | ≈ 89.2% | High — 50% Marriage Value Split with Freeholder |
| 75 Years | ≈ 85.5% | Severe — Surcharge compounding annually |
| 70 Years | ≈ 80.1% | Critical — Premium typically doubles vs 80-year mark |
| 60 Years | ≈ 70.4% | Extreme — Mainstream mortgageability compromised |
Following Earl Cadogan v Sportelli [2006], the Lands Tribunal established a benchmark deferment rate Sportelli case standard of 5.0% for flats and 4.75% for houses. The capitalisation rate leasehold valuation tribunal standard (5%–7%) discounts future ground rent streams. Higher deferment rates benefit the tenant by reducing reversion costs, while lower rates increase the overall premium.
The Leasehold and Freehold Reform Act 2024 commencement depends on secondary statutory instruments to bring premium changes into force. Key prospective changes include abolishing marriage value, replacing 90-year terms with 990-year extensions, and removing the 2-year ownership wait. However, because commencement remains pending, current statutory Section 42 notices operate under the 1993 Act rules.
Frequently Asked Questions
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Compare Specialist Leasehold Solicitors
Before serving a Section 42 notice, ensure your lease extension premium calculation is watertight. Compare verified quotes from RICS-accredited surveyors and specialist leasehold solicitors near you.
We may earn a commission on purchases at no extra cost to you. While we only partner with trusted platforms through reputable affiliate networks, all services and accounts are managed directly by the provider, who will handle any customer care or account needs.
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