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ONS coding system
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ONS coding system

The Office for National Statistics coding system is a hierarchical code used in the United Kingdom for tabulating census and other statistical data.

Table of contents
1 Authorities, wards, and census areas
2 Civil parishes
3 ONS codes for counties & districts
4 External link

Authorities, wards, and census areas

The code is constructed top down from a 4 character code representing a unitary authority or administrative county & district, eg:

00EC Middlesbrough (unitary)
12 Cambridgeshire county
12UB Cambridge district

Local Government wards have a two-letter code within their local authority, and census Output Areas an additional 4 digits within a ward. Output Areas are the smallest unit for which census data is published - they contain at least 40 households (preferably 100), and are built up from postcode blocks AFTER the census data is available with a view to being socially as homogeneous as possible. A new set of Output Areas will be created for each decennial census. Census 2001 was the first to use this system - previously census data was published for larger Enumeration Districts which were delineated before the census was conducted. Enumeration Districts are still used for the collection of data but not for publication.

12UB Cambridge district
12UBGA Petersfield Ward
12UBGA0001 Output Area: Gwydir Street (north of junction with Hooper St)

The authority and ward codes are recognised by Eurostat as Local administrative unit code levels 1 & 2 within the NUTS system.

Civil parishes

An overlapping system encodes Civil Parish areas. Parishes are represented by an additional 3 digits within their local authority:

12UD Fenland district
12UD010 Tydd St. Giles parish

ONS codes for counties & districts

Also showing NUTS(3) codes thus: (UKH12)

Single-tier districts

Two-tier counties & districts

Northern Ireland districts

Non-hierarchical codes for summary data in metropolitan areas

External link

ONS Beginners' Guide to UK Geography