The frequency of rent reviews depends greatly on the state of the property market and the economy at the time the lease is granted, as well as upon the trend within comparable leases in the locality. Both parties should obtain the expert opinion of a valuer.
The method of determining the new rent needs to be set out within the lease. Often parties first mention the Retail Price Index but although this will keep the rent in line with inflation, it does not relate to property values. Most frequently rent reviews aim to impose the open market rent prevailing at the time of the review and so the arbitration services of a valuer will be engaged. The precise terms or factors to be valued also need to be set out clearly, for example, are tenant's improvements to be disregarded?