Reviews to ‘market value’ are the most common form of rent review for commercial leases. Indexed-linked reviews are where the rent review is linked to an index, typically the Retail Price Index (RPI). Indexed-linked reviews are often used a substitute for market value in an attempt to keep the rent in line with market value, although such indices (i.e. RPI) bare no relation to property values. Indexes are mainly used for properties where there is little or no comparable evidence and can often lead to a reviewed rent being either grossly inflated or undervalued if adopted over a lengthy period of time.