Leasehold Extension Premium Calculator

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); the Midlands and North use higher rates (lower premiums).

This is what your flat is worth TODAY with its current short lease — not its freehold value. Use comparable recent sales on Rightmove/Zoopla or Land Registry Price Paid data. The tool will calculate the notional freehold value by reversing the relativity ratio.

Read your lease document or Land Registry title. The slider turns red once you cross the 80-year threshold — that’s the marriage-value cliff. Small differences around 80 produce large premium differences.

Peppercorn = £0. "Fixed" means the rent never changes. "Doubling every 25 years" or "every 10 years" trigger warnings — these clauses can make your flat unmortgageable. RPI-linked is intermediate.

The hero shows: total cost (premium + fees), value uplift (how much the flat becomes worth more post-extension), net benefit, and the cost of waiting 5 years. If net benefit is positive and urgency is "critical" or "soon", extend now.

Breakdown tab: see where the premium goes (term, reversion, marriage value, fees). Timing tab: see how the premium grows as the lease shortens, with your current position and the 80-year cliff marked. Process tab: the 7-step statutory timeline. Method tab: the formulas and limitations.

A 1993 Act premium has three parts. Term value compensates the freeholder for loss of ground rent during the remaining years — calculated as PV of annual ground rent. Reversion value compensates for loss of the property itself at lease-end — the freehold value discounted back at the deferment rate (typically 5% per Sportelli). Marriage value (only under 80 years) splits the benefit of the extension 50/50 between leaseholder and freeholder. For a typical Prime London flat at 78 years, marriage value alone is often £25,000–£50,000.

In Earl Cadogan v Sportelli [2006], the Lands Tribunal set a 5% deferment rate as the starting point for Prime Central London flats (4.75% for houses). Subsequent decisions have refined this for regional markets and specific property characteristics. A higher deferment rate reduces the reversion value (good for the leaseholder); a lower rate increases it. Tribunal valuers often debate ±0.25% — which can shift the premium by thousands.

Relativity % = value of the leasehold as a proportion of the freehold, assuming no Act rights. It’s used to calculate marriage value. Several competing relativity graphs exist: Savills (2002 updated), Gerald Eve (2016), Parthenia (2015, later criticised). Tribunals tend to prefer Savills or a blended graph. A 1-point relativity difference at 70 years can shift marriage value by £5,000+ on a £500,000 flat.

Use statutory (s.42) if: lease under 85 years, freeholder is uncooperative or unknown, ground rent is onerous, or you want the tribunal safety net. Use informal if: lease over 90 years, freeholder is a resident-owned management company, both sides agree on premium AND terms, you want speed over protection. When in doubt, statutory — it costs £500 more in fees but avoids £10,000 mistakes.

The Leasehold and Freehold Reform Act 2024 received Royal Assent May 2024 but its premium provisions need secondary legislation, expected late 2026 / 2027. When commenced: marriage value abolished (saving £10k–£50k for sub-80-year leases), 990-year extensions at peppercorn, no 2-year wait. For a leaseholder at 78 years today, waiting 18 months could save £30,000+ — but you drop to 76.5 years and the lease-length discount compounds. Rule of thumb: if you’re at 79–81 years, wait if you can; if you’re at 60–70 years, extend now under the current rules.