Global Express Entry now includes two optional new identifier fields in the GB response: The Unique Property Reference Number (UPRN) and Unique Delivery Point Reference Number (UDPRN).
The Unique Property Reference Number, or UPRN, identifies addressable locations in Great Britain. Its association with a property does not change. There are a few exceptions – such as if the address is for postal use only. In that case, no UPRN is issued. The UPRN is derived from Ordnance Survey’s data which is distinct from Royal Mail’s Postcode Address File (PAF).
The Unique Delivery Point Reference Number, or UDPRN, in turn identifies premises as opposed to locations. Similar to the way the UPRN is issued, each address in the Royal Mail PAF is associated with a UDPRN.
Further, UPRN and UDPRN are 1-1. So each address will have unique UPRN and UDPRN. Also, UDPRN’s are not deleted if the address changes (due to corrections, company name changes, or postcode modification), so they are useful as a persistent key.
These two fields are accessible by adding a simple REST parameter as part of any Melissa Data Subscription to Global Express Entry. The wiki has details:
https://wiki.melissadata.com/?title=Express_Entry:GlobalExpressFreeForm (for Free Form Input)
https://wiki.melissadata.com/?title=Express_Entry:GlobalExpressAddress (for Fielded Input)