ONS Postcode Directory
The ONS Postcode Directory (ONSPD) relates both current and terminated postcodes in the United Kingdom to a range of current statutory administrative, electoral, health and other area geographies. It also links postcodes to pre-2002 health areas, 1991 Census enumeration districts for England and Wales, 2001 Census Output Areas (OA) and Super Output Areas (SOA) for England and Wales, 2001 Census OAs and SOAs for Northern Ireland and 2001 Census OAs and Data Zones (DZ) for Scotland. It helps support the production of area based statistics from postcoded data. The ONSPD is produced by ONS Geography, who provide  geographic support to the Office for National Statistics (ONS) and geographic services used by other organisations. The ONSPD is issued quarterly. The ONSPD is available for free download in comma separated variable (CSV) format and ASCII text (TXT) formats from the ONS Open Geography Portal. The supplied file contains multi CSVs so that postcode areas can be opened in MS Excel. The ONSPD reflects current and terminated postcodes using information supplied monthly by Royal Mail. It relates postcodes (as at the third Friday of the month prior to each release) to administrative and electoral areas as at the preceding May  and to the latest known health areas. The area assignments for postcodes in Scotland are to the latest electoral wards and council areas. The area assignments for postcodes in Northern Ireland are to the latest electoral wards and district council areas. The ONSPD uses the Government Statistical Service (GSS) standard 9-character codes throughout and lookup files linking these codes to statutory area names are provided. Each record in the ONSPD contains the following fields: