How does the UK’s postcode system work?

14 Jul 2021 - Category: Blog /
UK’s postcode

Do you live in the UK? Or maybe you’ve visited and are planning to eventually move? Something you might have noticed is how dependent mobility and logistics are on postal codes. But, how are they decided and identified?

Postal Codes or postcodes in the UK are alphanumeric codes based on districts in the UK. They serve the purpose of sorting the mail by the GPO and also for insurance calculation and in-route planning software for designating destinations. As you can imagine, they’re quite important! Without postcodes the process of finding addresses would be tedious and not as reliable.

So, why does your address feature a seemingly random collection of letters and numbers? How did this system come about, and how does it work? In this blog we’ll explore how postal codes are distributed in the UK and what this might mean for you.

The Post Code System

The system was originally introduced by the Royal Mail to facilitate efficient and fast mail delivery. Today, there are about 30 million physical address locations where the Royal Mail delivers. And these addresses are based on postcodes.

A postcode is an essential part of administrative identity. If you want people to know where to send things, or if you need to fill in a form requiring your details, you’ll need a postcode.

You can find a postcode based on town or area name within the UK. In addition, you can look up information regarding any area or district depending on its postcode. Technology allows us to calculate the distance between two postcodes to find out how much time will be needed to reach your destination.

There are 121 postcode areas currently in use. Each area is assigned around 20 postcode districts on an average. London was divided into ten districts based on compass points, for example NW was the code for North West London and SE for South East London and these codes are still in use.

Structure of a Postcode

Postcodes are composed of two alphanumeric codes made up of three or four characters each. There are four elements of a UK postcode: Area, District, Sector and Unit. Each carries its own meaning. But don’t worry, it’s not too complicated!

The first part is known as the outbound code and the second one is called the inbound code. Each area in the UK, composed of several towns, is assigned a two-letter code. The name is usually chosen based on a major town in that area. The areas are then divided into postal districts, each one assigned a number. All these numbers and codes are unique.

Some of these outward codes are non-geographic and do not indicate location. However, in most cases the first letters and numbers indicate area. For example “L” refers to Liverpool, “EH” for Edinburgh and “BT” for Belfast. It’s a handy way of quickly identifying which city or area you’re referring to.

Each postcode covers up to 100 properties in a locality within a district. Postcodes are constantly being updated depending on addition of new properties or demolition of old ones. Some postcodes are changed, while others are deleted to keep the database up-to-date for efficient mail delivery.

For companies all around the world who offer delivery services, this neat postcode system is vital for product deliveries and general customer/user relationships.

The system of postcoding is hierarchical. In addition to a postcode, an address would include the building number or the house number to complete it. Just by looking at a postcode, the delivery system is able to identify the locality where they need to deliver the mail. It’s as simple as that!

Glasgow was also divided into compass districts like London. When the system was developed, an additional G code was added to differentiate between Glasgow and London. In major cities with millions of addresses it is particularly impressive that this system continues to be effective and it is an important way of establishing a geographical identity.

Non-Geographic Postcodes

There are some postcodes within the UK that are not based on any geographic location. They are also known as PO box numbers. Some online retailers also use the code XX for returns by Royal Mail. uses XX10 1DD and XX30 1FF for Scottish Distribution Centre and South West Distribution Centre respectively. ASOS, Boohoo and John Lewis have similar XX codes. This is useful to know for any customers who are dissatisfied with products and need to double-check that the return address is accurate.

You can find a complete list of postcodes online that are currently in use in the UK. In addition to mail delivery, the postcodes are also used to fetch statistics about a locality and to compare certain parameters. The details concerning postcodes are in public records and there are useful websites like Ideal Postcodes which anyone can use to find out more information about postcodes.

What is my postal code in the UK?

If you already have a postcode or you’re looking for the postcode of a friend or a family member you can search for them online. You can use the Royal Mail’s official website to find out anything you need to know about postcodes. There you can find out how to search for an address or postcode using Postcode Finder and how you can update or add your address to the database.

Postcodes are an important part of your identity when you’re interacting with deliveries, financial information and other official admin. So it’s vital that your postcode is accurate.

Alternatively, if you need a business address or you don’t want to share your home address you can get a PO Box and get your post sent there. Then you can maintain your normal post code for personal matters and keep a PO Box for collections.

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