GSS coding system

GSS codes are nine-character geocodes maintained by the United Kingdom's Office for National Statistics (ONS) to represent a wide range of geographical areas of the UK, for use in tabulating census and other statistical data. GSS refers to the Government Statistical Service of which ONS is part.

GSS codes replaced a previous system called ONS codes from January 2011. ONS codes were hierarchical whereas in GSS codes there is no relation between the code for a lower-tier area and the corresponding parent area.

Code formulation

GSS codes have a fixed length code of nine characters. The first three characters indicate the level of geography, and the six digits following define the individual unit. For example, the Royal Borough of Greenwich is coded as E09500011, Middlesbrough is E06000002, Cambridge E07000008 and Fenland E07000010.

As of December 2022, the meanings of some common three character prefixes are as follows:

England	Wales	Scotland	Northern Ireland	Other	Status	Entity
E00	W00	S00	N00	-	Current	Census Output Area (OA); Small Areas (N)
E01	W01	S01	–	-	Current	Lower layer Super Output Area (LSOA); Data Zone (S)
E02	W02	S02	–	-	Current	Middle layer Super Output Area (MSOA); Intermediate Zone (S)
E04	W04	S35	–	-	Current	Civil Parish (E/S); Community (W)
E05	W05	S13	N08	-	Current	Ward or Electoral Division
E06	W06	S12	–	-	Current	Unitary Authority
E07	–	–	–	-	Current	Non-Metropolitan District (two-tier)
E08	–	–	–	-	Current	Metropolitan Borough
E09	–	–	–	-	Current	London Borough
E10	–	–	–	-	Current	County
E11	–	–	–	-	Current	Metropolitan County
E12	–	–	–	-	Current	English Region
E13	–	–	–	-	Current	Inner and Outer London
E14	W07	S14	N06	-	Current	Westminster Parliamentary Constituency
E15	W08	S15	N07	-	Current	European Electoral Region
E16	-	-	-	-	Archived	Primary Care Trusts
E17	-	-	-	-	Archived	Care Trusts
E18	-	-	-	L00 / M00	Archived	Strategic Health Authorities
E19	-	-	-	-	Archived	Pan Strategic Health Authorities
E20	W12	-	-	-	Current	Cancer Registries
E21	W13	-	-	-	Archived	Cancer Networks
E22	W14	-	-	-	Current	Community Safety Partnerships
E23	W15	S23	N23	-	Current	Police Force Areas
E24	-	-	-	-	Archived	Local Learning and Skills Councils
E25	-	-	-	-	Current	Primary Urban Areas
E26	W18	S21	-	-	Current	National Parks
E27	-	-	-	-	Archived	New Deal for Communities
E28	W20	-	-	-	Current	Registration Districts
E29	W21	-	-	-	Current	Registration Sub-District
E30	W22	S22	N12	K01	Current	Travel to Work Areas
E31	W25	S38	N31	-	Current	Fire and Rescue Authorities
E32	W09	S16	–	-	Current	London Assembly; Welsh Assembly; Scottish Parliament Constituency
E33	W35	S34	N19	-	Current	Workplace Zones
E34	W37	-	-	K05	Archived	2011 Built Up Areas
E35	W38	-	-	K06	Archived	2011 Built Up Area Sub-Divisions
E36	W39	-	-	-	Current	Census Merged Wards
E37	-	-	-	-	Current	Local Enterprise Partnerships
E38	-	-	-	-	Current	Clinical Commissioning Groups
E39	-	-	-	-	Archived	NHS England
E40	-	-	-	-	Current	NHS England Regions
E41	W40	-	-	-	Current	Merged Local Authority Districts
E42	-	-	-	-	Current	Census Merged Counties
E43	-	-	-	-	Current	Non-Civil Parished Areas
E45	-	-	-	-	Current	Public Health England Centres
E46	-	-	-	-	Current	Public Health England Regions
E47	-	-	-	-	Current	Combined Authorities
E48	-	-	-	-	Current	Local Resilience Forums
E49	-	-	-	-	Current	Enterprise Zones
E50	-	-	-	-	Current	Waste Authorities
E51	-	-	-	-	Current	Development Corporations
E52	-	-	-	-	Current	LEP - overlapping part
E53	-	-	-	-	Current	LEP - non overlapping part
E54	-	-	-	-	Current	Integrated care boards (formerly Sustainability and Transformation Partnerships)
E55	-	-	-	-	Current	Strategic Clinical Networks
E56	-	-	-	-	Current	Cancer Alliances
E57	-	-	-	-	Archived	National Cancer Vanguards
E58	-	-	-	-	Current	County Electoral Divisions
E59	-	-	-	-	Current	Integrated Care Systems
E60	W43	S44	N13	-	Current	Local Planning Authorities
E61	-	-	-	-	Current	Greater London Authority
E63	W45	S45		K08	Current	2022 Built Up Areas
E92	W92	S92	N92	L93 / M83	Current	Country
E92	W92	S92	N92	-	Current	Country
-	-	-	-	J01	Current	Major Towns and Cities
-	-	-	-	J02	Current	1961 Census Parishes
-	-	-	-	J03	Current	1961 Census Wards
-	-	-	-	J04	Current	1961 Census Districts
-	-	-	-	J05	Current	1961 Census Counties
-	-	-	-	K02	Current	United Kingdom
-	-	-	-	K03	Current	Great Britain
-	-	-	-	K04	Current	England and Wales
-	-	-	-	L93 / M83	Current	British Crown Dependencies
-	-	-	-	M01	Current	Primary Healthcare Directorate
-	-	-	N09	-	Current	Local Government Districts
-	-	-	N10	-	Current	District Election Areas
-	-	-	N11	-	Current	Settlement 2015
-	-	-	N24	-	Current	Police Force Districts
-	-	-	N32	-	Current	Northern Ireland Fire and Rescue Service Areas
-	-	-	N33	-	Current	Northern Ireland Fire and Rescue Service Districts
-	-	-	N34	-	Current	City Regions
-	-	S03	-	-	Archived	Community Health Partnerships
-	-	S04	-	-	Current	Regeneration Outcome Agreement Areas - Scotland
-	-	S05	-	-	Current	Regeneration Outcome Areas - Community Planning Partnerships
-	-	S06	-	-	Current	Regeneration Outcome Areas - Local Areas
-	-	S07	-	-	Current	Regional Transport Partnerships
-	-	S08	-	-	Current	Health Board areas
-	-	S09	-	-	Current	Enterprise Regions
-	-	S10	-	-	Current	Urban Regeneration Companies
-	-	S11	-	-	Current	Strategic Development Plan Areas
-	-	S12	-	-	Current	Council Areas
–	W10	S17	–	-	Current	Welsh Assembly; Scottish Parliament Electoral Region
-	-	S19	-	-	Current	Localities
-	-	S20	-	-	Current	Settlements
-	-	S24	-	-	Current	Highlands and Islands Enterprise
-	-	S25	-	-	Current	Community Justice Authorities
-	-	S26	-	-	Archived	Community Health Partnerships sub-areas
-	-	S27	-	-	Current	ISD Health Board of Treatment
-	-	S28	-	-	Current	Census Detailed Characteristics
-	-	S29	-	-	Current	Census Local Characteristics
-	-	S30	-	-	Current	Local Administrative Units 1
-	-	S31	-	-	Current	Local Administrative Units 2
-	-	S32	-	-	Current	Scottish Police Divisions
-	-	S33	-	-	Current	Broad Rental Market Areas
-	-	S35	-	-	Current	Civil Parish
-	-	S36	-	-	Current	Island Groups
-	-	S37	-	-	Current	Integration Authorities
-	-	S39	-	-	Current	Scottish Fire and Rescue Local Senior Officer Areas
-	-	S40	-	-	Current	Scottish Fire and Rescue Service Delivery Areas
-	-	S41	-	-	Current	Scottish Marine Regions
-	-	S42	-	-	Current	Scottish Local Resilience Partnerships
-	-	S43	-	-	Current	Scottish Regional Resilience Partnerships
-	W03	-	–	-	Current	Upper layer Super Output Area (USOA)
-	W04	-	–	-	Current	Communities
-	W11	-	–	-	Current	Local Health Boards
-	W16	-	–	-	Current	Department for Children, Education, Lifelong Learning and Skills
-	W19	-	–	-	Current	National Assembly Economic Regions
-	W23	-	–	-	Current	Spatial Plan Areas
-	W24	-	–	-	Current	Spatial Plan Sub-areas
-	W26	-	–	-	Current	Strategic Regeneration Areas
-	W27	-	–	-	Current	Strategic Regeneration Sub-areas
-	W28	-	–	-	Current	Transport Consortia Areas
-	W29	-	–	-	Current	Agricultural Regions
-	W30	-	–	-	Current	Agricultural Small Areas
-	W31	-	–	-	Current	Non-National Park Area
-	W32	-	–	-	Current	Non-Strategic Regeneration Area
-	W33	-	–	-	Current	Communities First Areas
-	W34	-	–	-	Current	Non-Communities First Areas
-	W36	-	–	-	Current	Footprint Regions for Public Service Collaboration
-	W42	-	–	-	Current	City Regions

In 2019, the House of Commons Library proposed names instead of numeric codes for MSOAs to make them easier to use.

A full listing of GSS names and codes may be found by following the link to ONS Geography's Code History Database, below.

Geography of the UK Census

Information from the 2011 Census is published for a wide variety of geographical units. These areas include:

• Counties in England
• Districts within English counties, and unitary authority areas (where one council provides district and county functions)
• Unitary council areas in Wales, Scotland, and Northern Ireland
• Civil parishes (communities in Wales)
• Electoral wards (electoral divisions in Wales). These areas are defined for the election of local councillors, but are also widely used for presenting statistics at a smaller scale than the whole district.
• Census output areas (OA), the smallest unit for which census data are published. They were initially generated to support publication of 2001 Census outputs and contain at least 40 households and 100 persons, the target size being 125 households. They were built up from postcode blocks after the census data were available, with the intention of standardising population sizes, geographical shape and social homogeneity (in terms of dwelling types and housing tenure). The OAs generated in 2001 were retained as far as possible for the publication of outputs from the 2011 Census (less than 3% were changed). Before 2001, census data was published for larger Enumeration Districts (ED) which were delineated before the census was conducted and were the organisational units for census data collection.

Neighbourhood Statistics Geography

Super Output Areas (SOAs) are a set of geographical areas developed following the 2001 Census, initially to facilitate the calculation of the Indices of Deprivation 2004 and subsequently for a range of additional Neighbourhood Statistics (NeSS). The aim was to produce a set of areas of consistent size, whose boundaries would not change (unlike electoral wards), suitable for the publication of data such as the Indices of Deprivation. They are an aggregation of adjacent Output Areas with similar social characteristics. Lower Layer Super Output Areas (LSOAs) typically contain 4 to 6 OAs with a population of around 1,500. Middle Layer Super Output Areas (MSOAs) on average have a population of 7,200. The hierarchy of Output Areas and the two tiers of Super Output Areas have become known as the Neighbourhood Statistics Geography.

MSOAs use the name of the local or unitary authority followed by three digits, for example "Tower Hamlets 022" which is E02000885. LSOAs use the name of the containing MSOA followed by a letter, for example "Tower Hamlets 022C" which is E01004304.

Some LSOAs and MSOAs were revised in alignment with the 2021 Census.

Former hierarchical coding system

Main article: ONS coding system

The older ONS code was constructed top down:

• A two-character code represented a county.

For example, 12 for Cambridgeshire.

• A four-character code represented a district, so that the first two characters showed the county in which the district was placed.

For example, 12UB for Cambridge district or 12UD for Fenland.

• In the case of a unitary authority (including metropolitan and London boroughs) the first two digits were 00.

For example, 00AL for Greenwich (London Borough) or 00EC for Middlesbrough.

• Local Government wards were given a two-letter code within their local authority.

For example, 12UBGA for Petersfield Ward within Cambridge district.

• The smallest level, Census OAs were originally given an additional 4 digits within a ward, so that the first output area in Petersfield Ward was coded 12UBGA0001.
• Civil parishes were also coded using this hierarchical system. Parishes were coded using an additional 3 digits after their local authority. For example, within 12UD for Fenland district, the parish of Tydd St. Giles was coded 12UD010.

See also

• Geodemographic segmentation
• ONS Open Geography Portal

External links

• ONS Beginners' Guide to UK Geography
• Open Geography portal
• Code History Database downloads (2017 onwards)
• Mapit - shows ONS boundaries for any postcode