Our calculator is designed to give you an estimated range of the fair premium for a lease extension for a flat using the parameters of relativity derived respectively from data for settlements compiled by practitioners operating in Prime Central London (PCL) and by by practitioners operating in Greater London and England as set out within the RICS Research Document on Leasehold reform published October 2009. Investment and deferment yield rates used are 6.5% and 5% respectively. The choice of these typical rates is arbitrary and may be subject to fluctuation according to circumstances in each case which could impact significantly upon the amount of premium.

Figures indicated do not include additional costs likely to be payable by a leaseholder which include liability for the landlord's reasonable valuation and legal costs. A leaseholder should obtain estimates for these and other costs if applicable and budget accordingly before entering into the lease extension process. . The calculator does not make adjustment for a leaseholder's improvements, rising ground rents, non standard lease terms or any other variables which might affect the amount of premium properly payable.