The Company Registration Number or UKREG is a unique identifier applied by Companies House to all companies registered to do business in the United Kingdom.
Additional Information
Companies House also has introduced a simple Uniform Resource Identifier (URI) for all companies on its register. The URI is permanent and represents the company. When used as an internet address, it will return basic company details in a format appropriate for the requesting system. Companies House Glossary: http://www.companieshouse.gov.uk/infoAndGuide/glossary.shtml