Editing Postal code (section)

=== Precision ===
==== Czechoslovakia ====
Czechoslovakia introduced Postal Routing Numbers (PSČ – poštovní směrovací čísla) in 1973. The code consists of 5 digits formatted into two groups: NNN NN. Originally, the first group marked a district transport centre, the second group represented the order of post offices on the collection route. In the first group, the first digit corresponds partly with the region, the second digit meant a collection transport node (sběrný přepravní uzel, SPU) and the third digit a "district transport node" (okresní přepravní uzel). However, processing was later centralized and mechanized while codes remained the same. After separation, Slovakia and the Czech Republic kept the system. Codes with an initial digit of 1, 2, 3, 4, 5, 6, or 7 are used in the Czech Republic, while codes with an initial digit of 8, 9, or 0 are used in Slovakia.

A code corresponds to a local postal office. However, some larger companies or organizations have their own post codes. In 2004–2006, there were some efforts in Slovakia to reform the system, to get separate post codes for every district of single postmen, but the change was not realized.

====India====
{{Further|Postal Index Number}}

[[File:Example of Indian Postal Index Number.svg|thumb|An example of a Postal Index Number from [[Ujjain]] in [[Madhya Pradesh]]. '''4''' indicates the ''West postal zone'', '''5''' indicates ''a postal sub-zone in Madhya Pradesh'', '''6''' indicates the ''Ujjain sorting district'', '''0''' indicates the ''Ujjain core area service route'', '''01''' indicates the ''Ujjain Head Office as the delivery office''.]]

Postal codes are known as [[Postal Index Number]]s (PINs; sometimes as PIN codes) in India. The PIN system was introduced on 15 August 1972 by India Post. India uses a unique six-digit code as a geographical number to identify locations in India. The format of the PIN is ZSDPPP defined as follows:

: Z – Zone
: S – Sub-zone
: D – Sorting District
: P – Service Route
: PP – Post Office

The first digit represents nine total zones: eight regional and one functional.

==== Ireland ====
{{Further|Postal addresses in the Republic of Ireland}}

In Ireland, the new postal code system launched in 2015, known as [[Eircode]] provides a unique 7-character alphanumerical code for each individual address. The first three digits are the routing key, which is a postal district and the last four characters are a unique identifier that relates to an individual address (business, house or apartment). A fully developed API is also available for integrating the Eircode database into business databases and logistics systems.

With a single exception, these codes are in the format:

ANN XXXX

The single exception is the Dublin D6W postal district. It is the only routing key area in the country that takes the format ANA instead of ANN:

D6W XXXX

While it is not intended to replace addresses, in theory simply providing a seven-character Eircode would locate any Irish delivery address. For example, the Irish Parliament [[Dáil Éireann]] is: D02 A272

==== Netherlands ====
{{further|Postal codes in the Netherlands}}

[[Postal codes in the Netherlands]], known as postcodes, are alphanumeric, consisting of four digits followed by a space and two letters (NNNN AA). Adding the house number to the postcode will identify the address, making the street name and town name redundant. For example: 2597 GV 75 will direct a postal delivery to Theo Mann-Bouwmeesterlaan 75, [['s-Gravenhage]] (the International School of The Hague).

==== Singapore ====
{{Further|Postal codes in Singapore}}

Since 1 September 1995, every building in Singapore has been given [[postal codes in Singapore|a unique, six-digit postal code]].<ref name="Singapore NLB" />

==== United Kingdom ====
{{More citations needed section|date=January 2025}}
{{Further|Postcodes in the United Kingdom}}
For domestic properties, an individual postcode may cover up to 100 properties in contiguous proximity (e.g. a short section of a populous road, or a group of less populous neighbouring roads). The postcode together with the number or name of a property is not always unique, particularly in rural areas. For example, GL20 8NX/1 might refer to either 1 Frampton Cottages or 1 Frampton Farm Cottages, roughly a quarter of a mile (400 metres) apart.

The structure is alphanumeric, with the following six valid formats, as defined by [[British Standards|BS]] 7666:<ref>{{cite web |title=BS7666 Address |work=Data Standards Catalogue |publisher=UK National Archives |date=2 October 2009 |url=http://www.cabinetoffice.gov.uk/govtalk/schemasstandards/e-gif/datastandards/address/postcode.aspx |archive-url=http://webarchive.nationalarchives.gov.uk/20130128101412/http://www.cabinetoffice.gov.uk/govtalk/schemasstandards/e-gif/datastandards/address/postcode.aspx |url-status=dead |archive-date=28 January 2013 |access-date=15 August 2015 }}</ref>

   AN NAA
  ANA NAA
  ANN NAA
  AAN NAA
 AANA NAA
 AANN NAA

There are always two halves: the separation between outward and inward postcodes is indicated by one space.

The outward postcode covers a unique area and has two parts which may in total be two, three or four characters in length. A postcode area of one or two letters, followed by one or two digits, followed in some parts of London by a letter.

The outward postcode and the leading numeric of the inward postcode in combination forms a postal sector, and this usually corresponds to a couple of thousand properties.

Larger businesses and isolated properties such as farms may have a unique postcode. Extremely large organisations such as larger government offices or bank headquarters may have multiple postcodes for different departments.

There are 121 postcode areas in the UK, ranging widely in size from [[BT postcode area|BT]] which covers the whole of Northern Ireland to [[WC postcode area|WC]] for a small part of [[Central London]]. Postcode areas occasionally cross national boundaries, such as [[SY postcode area|SY]] which covers a large, predominantly rural area from [[Shrewsbury]] and [[Ludlow]] in [[Shropshire]], England, through to the seaside town of [[Aberystwyth]], [[Ceredigion]] on [[Wales]]' west coast.  There are a number of special purpose postcode areas that are "non-geographic" and which provide special routing instructions (such as parcel returns to online retailers).  The three Crown dependencies and Gibraltar also use UK formatted postcodes.  Some British Overseas Territories have adopted a single postcode for their territory that is very similar to the UK format.

==== United States ====
{{further|ZIP Code}}

In the United States, the basic [[ZIP Code]] is composed of five digits. The first three digits identify a specific [[sectional center facility]]—or central sorting facility—that serves a geographic region (typically a large part of a state). The next two digits identify a specific post office either serving an area of a city (if in an urban area or large suburban area) or an entire village, town, or small city and its surrounding area (if in a small suburban or rural area).

There is an extended format of the ZIP Code known as the [[ZIP+4]], which contains the basic five-digit ZIP Code, followed by a hyphen and four additional digits. These digits identify a specific delivery route, such as one side of a building, a group of apartments, or several floors of a large office building. Although using the ZIP+4 offers higher accuracy, addressing redundancy, and sorting efficiency within the [[USPS]], it is optional and not widely used by the general public. It is primarily only used by business mailers.

For high volume business mailers using automated mailing machines, the USPS has promulgated the [[Intelligent Mail barcode]] standard, which is a barcode containing the ZIP+4 code plus a two digit [[delivery point]]. This 11-digit number is theoretically a unique identifier for every address in the country.