Lease Extension Calculator

1. The 80-Year Threshold — Why It Matters

The single most important principle of lease extension in England and Wales is the 80-year threshold. Under the Leasehold Reform, Housing and Urban Development Act 1993 (as amended), when a lease falls below 80 years, leaseholders must pay 'marriage value' — 50% of the uplift in property value created by the extension.

What is marriage value? Marriage value represents the difference in property value between the current short lease and the extended lease. A flat worth £300,000 with an 85-year lease might be worth £340,000 with a 990-year lease — a marriage value of £40,000. Below 80 years, the leaseholder pays 50% (£20,000) as part of the extension premium. Above 80 years, no marriage value is payable.

The compounding problem: Every year a lease sits below 80 years, the property value declines (because the unexpired term is shorter), increasing the marriage value calculation. A flat on 75 years deteriorating to 70 years can see the premium increase by 15–25%. The cost of delay compounds quickly and the property becomes harder to mortgage or sell.

Leasehold and Freehold Reform Act 2024: This Act includes a provision to abolish marriage value entirely, meaning the 80-year threshold will cease to have special significance once this provision comes into force. As of March 2026, the abolition of marriage value has not yet been commenced — check the current implementation status with your solicitor.

2. The Section 42 Formal Extension Process

The formal lease extension route under Section 42 of the 1993 Act gives qualifying leaseholders a legal right to extend by 90 years on top of the current unexpired term, at a peppercorn (zero) ground rent. This statutory right cannot be refused by the freeholder — only the price is negotiable.

Qualifying conditions: You must have owned the flat (as registered proprietor) for at least 2 years prior to serving notice. The property must be a flat (not a house). It must be residential. There is no qualification period based on how long the lease was originally granted. Shared ownership leaseholders may be able to use Section 42 but should take specialist advice.

The process step by step: (1) Instruct a RICS-qualified leasehold surveyor to value the premium. (2) Instruct a solicitor experienced in leasehold reform. (3) Serve the Section 42 notice on the correct party (usually the freeholder, though if there is an intermediate landlord, the notice may need to go to them). The notice must specify a premium you are proposing to pay. (4) The freeholder has 2 months to serve a counter-notice. (5) Negotiate price — the surveyor will handle this. (6) If no agreement after 6 months from counter-notice, either party applies to the First-tier Tribunal (FTT). (7) Completion typically takes 4–12 months from notice to completion.

Costs you pay: Your solicitor, your surveyor, SDLT if applicable (rare — peppercorn extension), Land Registry fee, and the freeholder's reasonable legal and surveyor costs (capped under the 2024 Act once provisions commence).

3. Informal vs Formal Route — Choosing Correctly

While the formal Section 42 route is most secure, many lease extensions are completed informally through direct negotiation. Understanding the pros and cons of each route is essential.

Informal route advantages: Speed — can complete in 4–8 weeks vs 4–12 months formally. Lower legal costs (no statutory notice process). Flexibility — can agree any term (not just 90 years extra), any ground rent structure (though new Ground Rent Act restrictions apply), and any conditions. Some freeholders offer better informal prices to avoid the formal process. Can negotiate before you own the property for 2 years (not possible formally).

Informal route risks: No statutory price protection — the freeholder can ask any price. The freeholder can walk away from negotiations at any time. You may pay too much if you don't use a surveyor. The extended lease may contain unfavourable terms not present in a statutory extension. You cannot switch to the formal route during informal negotiations without losing the goodwill already built.

Best practice for informal extensions: Always get a RICS surveyor to assess the fair premium before opening negotiations. Draft the extension through a solicitor, not just the freeholder's solicitor. Compare the informal offer to the statutory valuation. If the informal offer is within 10–15% of the statutory premium, and timeline/flexibility benefits exist, the informal route is often optimal.

4. Leasehold Reform Act 2024 — What Has Changed

The Leasehold and Freehold Reform Act 2024 represents the most significant reform of leasehold law in England and Wales since the 1993 Act. Key changes relevant to lease extensions include:

990-year standard extension: Qualifying leaseholders will be entitled to a 990-year extension (up from the current 90 years on top of the existing term). This removes any ongoing need to re-extend and effectively creates near-permanent ownership of the leasehold interest.

Abolition of marriage value: The Act provides for the abolition of marriage value, removing the 80-year threshold premium. Once this provision is in force, the statutory premium will consist only of the deferred freehold reversion value and the ground rent capitalisation — making extensions significantly cheaper for sub-80-year leaseholders. Timing of commencement was not confirmed as of March 2026.

Standard relativity tables: RICS will prescribe standard relativity tables for use in all valuations, ending the costly disputes about which table applies. This alone could save leaseholders £1,000–£5,000 in surveyor costs on contested cases.

Freeholder cost caps: Leaseholders will no longer be required to pay unreasonable freeholder legal costs. Costs will be capped at levels set by secondary legislation, preventing freeholders from inflating costs as a negotiating tool.

5. Mortgage Implications — Critical Thresholds

Lease length has direct implications for mortgage availability. Most UK mortgage lenders impose minimum lease length requirements at completion, and failure to meet these can make a property unmortgageable — dramatically impacting sale value.

Standard lender requirements (2026): Most high-street lenders require a minimum of 70 years remaining on the lease at completion. However, many lenders (including Halifax, Nationwide, Santander) require the lease to have at least 85 years remaining to offer standard rates. Below 70 years: very limited lender availability, higher rates, may require specialist broker. Below 60 years: effectively unmortgageable with mainstream lenders.

The practical rule: Ensure your lease has at least 85 years remaining when you sell, to maximise the pool of buyers and lenders. For a property currently at 82 years, extending now gives a 90+82 = 172-year extended term — well above any lender threshold. Waiting 5 years to a 77-year lease means paying marriage value and only extending to 167 years — a more expensive outcome for no additional benefit.

New purchase with short lease: If you are buying a flat with under 80 years remaining, factor the lease extension cost into your purchase price negotiation. Standard practice is to negotiate a price reduction equivalent to the extension premium, then extend after completing (once you have owned for 2 years). Some buyers simultaneously contract to buy and the seller assigns their rights under a Section 42 notice already served — allowing immediate extension completion. Always use specialist solicitors for this procedure.

6. Typical Cost Breakdown and How to Minimise Costs

Understanding the full cost breakdown of a lease extension prevents surprises and helps you budget accurately.

The premium: This is the payment to the freeholder — calculated using the statutory valuation formula. For a flat worth £350,000 with an 82-year lease and £250 annual ground rent, the premium is typically in the range of £8,000–£16,000 depending on yield rate and specific relativity. Our calculator provides a range estimate; only a RICS surveyor can give a precise valuation.

Your professional costs: Solicitor: £1,500–£3,500 (+ VAT). RICS valuer: £600–£1,500. Total: £2,500–£5,500. These are non-negotiable essentials — never proceed without professional representation.

Freeholder costs: Under the 1993 Act, leaseholders pay the freeholder's reasonable legal and valuation costs. Historically this has been £1,500–£3,500 combined. The 2024 Act will cap these, but until caps are set by secondary legislation, negotiate on these costs.

Cost minimisation strategies: (1) Act before marriage value applies (keep above 80 years). (2) Use a surveyor experienced in the specific area — they will know comparable premiums and negotiate more effectively. (3) Negotiate informally first to avoid formal process costs if the freeholder is reasonable. (4) Collective enfranchisement (buying the freehold collectively with other leaseholders) can be cheaper per flat than individual extensions for blocks of 4+ flats. (5) Compare extension cost vs freehold purchase — sometimes buying the freehold costs similar to an extension and gives full ownership.