The Metering System ID (MSID) for a site which is to be registered for Settlement in the Central Metering Registration Service (CMRS) is a unique four digit number which is used to identify the Central Volume Allocation (CVA) Metering System; for a site which is to be registered for Settlement in the Supplier Metering Registration Service (SMRS) is a unique number relating to a Metering Point and which consists of the following: (i) a 2 digit number determined by reference to the Licensed Distribution System Operator; (ii) a 10 digit reference number provided by the relevant Licensed Distribution System Operator; (iii) a 1 digit check number provided by the relevant Licensed Distribution System Operator.