Lease Extension Calculator — The Real 2026 Rules, Honestly

Every proper lease extension calculator works from the same three-part formula that tribunals actually use: the ground rent element (the capitalised value of the ground rent income the freeholder gives up), the reversion element (the deferred value of eventually getting the property back, pushed 90 years further into the future), and — for leases under 80 years — marriage value.

Marriage value is 50% of the increase in your property's value that results from extending the lease. It applies specifically when your unexpired term is below 80 years — and it's genuinely the single biggest cost driver in the entire calculation once you cross that threshold.

Notice the jump between 80 and 70 years — that's marriage value doing real work. If your lease is anywhere close to 80 years, extending before it drops below that threshold can genuinely save tens of thousands of pounds.

A statutory extension, under Section 42 of the Leasehold Reform, Housing and Urban Development Act 1993, gives qualifying leaseholders a legal right to extend their lease by 90 years on top of the current unexpired term, with ground rent reduced to a peppercorn — effectively zero — for the remainder. This right cannot be refused by the freeholder; only the price is genuinely negotiable, and ultimately determined by the First-tier Tribunal if you can't agree.

This is genuinely worth being direct about, because a lot of content online implies these changes have already happened. The Leasehold and Freehold Reform Act 2024 received Royal Assent in May 2024, and its headline provisions would genuinely transform lease extension costs: marriage value abolished entirely, the statutory term extended from 90 to 990 years, and a standardised valuation methodology reducing scope for dispute.

None of these provisions are in force as of 2026. They require secondary legislation that hasn't yet been laid before Parliament, and government guidance has indicated the headline reforms aren't expected to take effect before late 2027 or 2028 — considerably later than many people assumed when the Act first passed. If your lease is dropping toward 80 years now, waiting for a reform that may still be years away is a genuinely risky strategy — the marriage value cost of waiting could easily exceed any saving from reform, especially if your lease crosses the 80-year threshold in the meantime.

Under the statutory process, you're required to pay both your own legal and surveying costs and the freeholder's — a detail that genuinely surprises a lot of leaseholders. Budget realistically for £1,500 to £3,500 for your own solicitor, a further £1,500 to £3,500 for the freeholder's solicitor, and £1,000 to £2,500 for a surveyor's valuation. Combined with the premium itself, a typical statutory extension costs somewhere between £8,000 and £40,000 all-in, heavily dependent on how many years remain.

A flat worth £400,000 with 75 years remaining and £250 annual ground rent. Ground rent capitalised: roughly £2,600. Reversion value: roughly £9,800. Since 75 years is below the 80-year threshold, marriage value applies: roughly £6,000. Total premium: approximately £18,400, before fees.

Add typical fees — say £2,500 own solicitor, £2,500 freeholder's solicitor, and £2,000 surveyor — and the all-in cost comes to roughly £25,400. Had this same flat been extended two years earlier, at 77 years remaining but still under 80, the marriage value would still apply but at a slightly lower amount — illustrating why the years-remaining figure matters more than almost anything else in this calculation.

Official sources & further reading: read general leasehold guidance at GOV.UK, and find a RICS-qualified surveyor via the Royal Institution of Chartered Surveyors. Check your borrowing power for the extension costs with our mortgage affordability calculator, or browse every tool on the mortgage calculators homepage.