UK Postcode

UK Postcode is a combination of letters and numbers. A Postcode defines four different levels of a geographic unit. Each Postcode consists of two parts, called the postcode_outcode (e.g. ‘PL1’) and the postcode_incode (e.g. ‘1AR’). The first part is called postcode_outcode, and is separated from the second part is called postcode_incode, by a single space.

For Example- Postcode – PL1 1AR

Postcode_outcode – PL1

Postcode_incode –1AR

A comprehensive outline of UK postcode patterns, their constituent components, and how they can be utilized. Split a postcode into postcode_outcode, postcode_incode, postcode area, district code, sub-district code, and postcode sector and the postcode unit. Postcodes are an abbreviated form of address, and enable a group of Delivery Points to be specifically identified.

Postcode Format

Postcodes should always be in BLOCK CAPITALS as the last line of an address. Do not underline the postcode or use any punctuation. Leave a clear space of one character between the two parts of the postcode and do not join the characters in any way. The following list shows all valid Postcode formats. “A” indicates an alphabetic character and “N” indicates a numeric character.

Postcode Components

Postcodes can also be broken down into meaningful constituent components.


The Postcode_outcode is the first half of a postcode (before the space). The first part is known as the Postcode_outcode. Some are non-geographic, i.e. does not divulge the location.

Distinguishing features include: –

  • 2–4 characters long
  • Always begins with a letter
  • May end with a number or letter

Examples of Postcode_outcode include:

  • B1
  • PL1
  • BD13
  • W1B
  • SE1P


The Postcode_incode is the second half of a postcode (before the space). The second part is known as the Postcode_incode. This part is one number followed by two letters. The inward code assists in the delivery of posts within a postal district. The number identifies the sector in the postal district. The letters then define one or more properties in that sector.

Distinguishing features include: –

  • Exactly 3 characters long
  • Always begins with a number

Examples of Postcode_incode include:-

  • 2LX
  • 1JQ
  • 0AB
  • 9ZR
  • 2NT

Postcode Area

The postcode area is the longest initial string of letters in a postcode. A Postcode Area Code can be one or two letters. Postcode Area is part of the postcode_outcode.

Examples of Postcode Areas include:

  • CB (Cambridge)
  • DL (Darlington)
  • N (North London)
  • BB (Blackburn)

District Code

The district code is part of the postcode_outcode code. It is between two and four characters long. It does not include the trailing letter found in some outcodes.

Examples of Postcode District codes include:

  • E1
  • W2
  • DD7
  • TQ14
  • DH1

Sub-District Code

The sub-district code is part of the postcode_outcode. It is often not present, only existing in particularly high-density London districts. It is between three and four characters long. It does include the trailing letter omitted from the district.

Examples of Postcode Sub-District codes include:

  • WC2H
  • E1W
  • EC1M
  • N1C
  • NW1W

Postcode Sector

The postcode sector is made up of the postcode district, the single space, and the first character of the postcode_incode. It is between four and six characters long (including the single space).

Examples of the Postcode sector include:

  • SW1W 0
  • L1 8
  • CV1 4
  • GU16 7
  • PO16 7


The postcode unit is the last two letters of a postcode, which identifies one or more Small User Delivery Points or an individual Large User.

Each postcode unit generally represents:

  • a street
  • part of a street
  • a single address
  • a group of properties
  • a single property
  • a sub-section of the property
  • an individual organization or (for instance Driver and Vehicle Licensing Agency)
  • a subsection of the organization

Examples of Postcode Units include:

  • AR (from PL1 1AR)
  • EE (from B10 0EE)
  • YX (from RM8 2YX)
  • AF (from KA11 1AF)
  • TE (from L1 2TE)