Product details

Postcodes

There are two main components of a postcode:

• The outward code (also called outcode): The first two to four characters of the postcode constitutes the postcode area and the postcode district. It is the part of the postcode that enables mail to be sent from the accepting office to the correct area for delivery.

• The inward code (also called incode): The last three characters of the postcode constitutes the postcode sector and the postcode unit. It is used to sort mail at the local delivery office.

For example:

When used in an address, the incode should be separated from the outcode by a single space. The following table is a list of the valid formats of postcodes (an A indicates an alphabetic character; an N indicates a numeric character):

Postcode polygon geometry

Postcode polygons are produced by the tessellation of georeferenced PAF coordinates for individual Royal Mail delivery addresses. Only addresses having a positional quality value indicating the location is within a building are used to create the polygons file. Postcodes of addresses of lower quality will be included in the discard files.

Due to the nature of postcode geography, the polygons representing some postcode units are unavoidably split. Every effort has been made to ensure the absolute minimum of postcodes is represented by multiple polygons. These split polygons representing a single postcode remain a single object with one set of attributes.

Each polygon is assigned a unique identifier. The identifier will be a 16-digit series. These identifiers are not reused should a polygon be deleted.

The polygon dataset contains non-overlapping polygon coverage of Great Britain, originally constrained by the extent of realm (EOR) coastline from Ordnance Survey’s Boundary-Line data and postcode polygons. Should any addresses fall outside the constraining datasets, the postcodes should be included in the discard files.

For Shapefile, TAB and MID / MIF supply formats the data is divided into 120 postcode area files, each file named with a one or two letter postcode area code, and for vector tiles and GeoPackage supply formats, the data is provided as one national file.

Vertical streets

Postcodes that are vertically stacked, that is, two or more postcodes within a single building that are represented by a single large-scale building seed. In these situations, a single square polygon represents all the postcodes attributed to the single building seed. These polygons have a special series of identifiers, all commencing with the letter V.

A separate vertical streets lookup table is provided with the polygons and lists the postcodes with the 20-digit unique identifier that are represented by each special polygon. Where these distinctive polygons are crowded closely together, they are reduced in size to prevent overlaps hiding some of the polygons.

Data capture

The polygon set contains a polygon for every postcode in England, Scotland and Wales that is contained in Royal Mail’s PAF product, with the following exceptions:

• Postcodes for which there is no location data of sufficient quality.

• Postcodes for which there is no data that lies within the extent of the realm coastline.

• Postcodes that relate to PO Boxes.

• GeoPlace geocode the PAF data from Royal Mail, using source coordinates from Local Authorities in England, Wales and Scotland and Ordnance Survey. GeoPlace then provide the georeferenced PAF data to Ordnance Survey.

Coordinate reference systems

The Coordinate Reference Systems (CRS) of the polygon data is provided in British National Grid (BNG), (EPSG: 27700), with the exception of the vector tile polygon data which is provided in Web Mercator Projection (EPSG: 3857) For more information on the Code-Point CRS, see the Technical Specification here.

BNG uses the OSGB36 geodetic datum and a single Transverse Mercator projection for the whole of Great Britain. Positions on this projection are described using Easting and Northing coordinates in units of metres. The BNG is a horizontal spatial reference system only; it does not specify a vertical (height) reference system.

Currency

Updates are supplied quarterly in January, April, July and October, and are a complete resupply of the national dataset.

Each edition of Code-Point with Polygons will have a version number showing the release month for the year (for example, April) followed by the release year (for example, 2022).

The version for each quarterly release will be in this format:

• April_2022

• July_2022

• October_2022

• January_2023

The Code-Point data packaged alongside the postcode polygon data will be the data from the most recent Code-Point product release. Typically, this is the Code-Point release from two months prior. For example, the October 2022 release of Code-Point with Polygons will be supplied alongside the August 2022 release of Code-Point.