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Code History Database (CHD)

The CHD provides details of individual codes, relationships, hierarchies and archived geographies and their metadata. The database provides multiple functionality and enables users to view or export data for the following options:

  • Geography Listings contains both terminated and live entities, and instance codes, for geographies where new codes are available

  • Geography History contains the change history, where new codes have been allocated, from 1 January 2009

  • Geography Hierarchies provides the hierarchies for all entity themes where a one-to-one relationship exists

  • Geography Constitutions are provided for some geographies in England and Wales. These include parish to ward, electoral and health constitutions

  • Geography Equivalents provides the new codes and previous ONS, CLG, DH and other equivalent names and codes where available

  • Geography Information contains information about the geographies including Statutory Instrument Information

Further information about the geographies within the CHD can be found in the 'Beginner's Guide to geography

Product details

The CHD is in MS Access 2002 format.

For those who do not have Access as part of their desktop, there are csv name and code and lookup files available to download free of charge from the Open Geography portal.  These files are supplied with metadata, product specification and any other associated documentation in one zip file.


The current MS Access zip file and csv zip files are available and can be downloaded free of charge from the Open Geography portal.

Please save the CHD to your hard drive to ensure you have access to complete database functionality.

Please note that some users may experience slow download times when trying to open the files due to the size.

NOTE: If using MS Access 2007 an Information bar appears warning that certain content in the database has been disabled. To rectify this click on the Options button next to the warning message and then the radio button 'Enable this content'. To enable the export of data from the CHD click the drop down arrow located to the right of the Office button (top left of screen) and select  'Customise the quick access toolbar'. Select the 'More commands' option and 'Export to Excel spreadsheet' or your preferred alternative.


Content from the Office for National Statistics.
© Crown Copyright applies unless otherwise stated.