The UK Postcode System


To many foreign mailers, the UK postcode system is incomprehensible. Since they don't understand it, many of them don't use it, and thus cost themselves £millions in lost revenue and wasted postage. No other country has such a complex postcode system as the United Kingdom.

Within the Royal Mail, there is a section they call the: Blind Letter Duty. Officially, it is called: The Vaguely Addressed Mail Section. Other countries may know it as the Dead Letter Box. The Royal Mail's Blind Letter Duty used to be the best in the world and maintained a 24/7, 264 days-a-year service. With recently introduced competition, and economy cuts to the bone in pursuit of profit, this has changed. It is now a 9am to 4pm five-day-a-week service. Nowadays, the Royal Mail is more inclined to stamp an item: "Return to Sender", than open a page in a reference book. Understand the way the UK postcode system works, and you or your company will benefit. If you don't want to flush money down the toilet, you really have to sit up and pay attention in a way you never had to before.

Typical UK Postcodes

A UK postcode is a two-part code - an Outward Code and an Inward Code. As an example, let's invent one - TW1 2XA. The TW1 is the Outward Code, and ensures the letter gets to the town of Twickenham. The Inward Code - 2XA is for the convenience of the Royal Mail. The Inward Code helps direct the item to the postperson who is going to deliver to that address. It would be nice to have the complete postcode. But sorters are quite happy to have only the Outward Code. With this information, they can forward the item to an LDO (Local Delivery Office) and let the LDO deal with it using their knowledge - after all, that's what postmen and women are proud of - knowing their local community!

What makes the UK postcode system so unique is that there are three different systems in operation: single letter codes for certain major cities, two letter codes for other towns and cities, and a zone system which applies to London only:

Single letter codes
They are: B for Birmingham, G for Glasgow, L for Liverpool, M for Manchester, and finally, S for Sheffield.
Two letter codes
Two letter codes refer to a town or an area - a full list is given below. TW refers to Twickenham and surrounds; SN refers to Swindon and surrounds.
London - the zone system
London is different from the rest of the country. It is divided into zones, and they are: E - East London, EC - East Central London, N - North London, NW - Northwest London, SE - Southeast London, SW - Southwest London, W - West London, and finally WC - West Central London. Confusing, isn't it? But you have to work within the UK postcode system, otherwise you will be throwing money away. This website is here to help you save money.
Central London (W, WC, EC) Outward Codes often have an additional letter attached, for example WC1S, or EC2Y. Don't worry too much about it! If you've got the bare Outward Code, your letter should get to the intended address.

Hopefully, this site will help users both here and abroad to understand our postal system. Together with the Postcode Finder, which registered subscribers can use, your mail should in future get through, whereas in the past it was stamped 'Return to Sender - Insufficient Address' or words to that effect. Here are some (mostly) fictitious examples of what a UK address should look like.

The Single Letter Cities

  • S. Smith
  • 19 Melksham Street
  • Birmingham
  • B2 4AH
  • Ms A Andrews
  • 125 Dumbarton Road
  • Glasgow
  • G1 9XT
  • Mr J Adams
  • 27 Farm Road
  • Sheffield
  • S2 5XY
  • Mrs T Alexander
  • 239 St James Road
  • Manchester
  • M7 4AL

The Two-Letter Towns and Cities

  • A Jones
  • 9 Market Rd
  • Cardiff
  • CF5 8EJ
  • Mr J Blackburn
  • 89 Fortress Road
  • Plymouth
  • Devon
  • PL4 6ER
  • F Stapleton
  • 42 Quadrant Square
  • Southampton
  • SO5 4EQ
  • Ms Y Quedrue
  • 56 Lancaster Place
  • Nottingham
  • NG4 2QE

The London Zoned System

  • J Thomas
  • 126 Holloway Road
  • London
  • N7 2EQ (see note below)
  • JP Morgan (This is a genuine address)
  • 125 London Wall
  • London
  • EC2Y 5AJ
  • Meridien Enterprises Ltd
  • 30 Chelsea Road
  • London
  • SW3 2EH
  • HSBC Bank (This is a genuine address)
  • Canada Place
  • Canary Wharf
  • London
  • E14 5HQ

Note: the London postcode zones N1 thru N22 (such as in the example above: (N7 2EQ) are often perceived by foreigners as an abbreviation for 'Number', when in fact it is shorthand for 'North'. Never spell out a postcode as this will only confuse the machines.

The Counties

An address may often include a county. By tradition English, Scottish, and Welsh counties are known by name only: Kent, Essex, Wiltshire, Lanarkshire, Denbighshire, etc, - the only exception being County Durham because there is a city of the same name - Durham City.

Northern Ireland counties usually have "Co." preceding the name of the county, e.g.: "Co. Fermanagh, Co. Tyrone", etc. Note also that the whole of Northern Ireland has only one postcode prefix - BT for Belfast, but this does not imply the location is anywhere near Belfast. In this respect, BT serves as an area postcode in much the same way as HS for the Hebrides and ZE for the Shetland Isles. Clicking on the link below will give an interesting insight into the evolution of the British Counties during the last thirty years or so, courtesy of Jonathan Rawle:

For UK mailers, a special word of warning. If you think you don't need a postcode because you're posting a letter to a local address, think again! Gone are the days of local filtering. If you live in the Sheffield area, and the local Sheffield Mail Centre is overwhelmed, it will divert its traffic to another Mail Centre, and that may be as far away as London! Mail Centre managers have large screens in front of them and can tell at any time which Mail Centres are at full capacity, and which can handle more work when diverting mail to another Mail Centre. With inter-city hopping planes and good road links, distance is not a problem. We cannot emphasize the fact strongly enough - always use at least the minimum the Outward Postcode. If the item is intended for a local Sheffield address but was sidetracked to another Mail Centre, provided it has an Outward Postcode, there will be little or no delay. But if there is no Outward Postcode, the delay can be days or even weeks. The Royal Mail can even pulp the item!

Outward Postcode Prefixes

Below is listed every possible Outward Postcode prefix, the town, city, or area they are derived from, the county where that town, city, or area is located, and the usual abbreviation for the county. The major cities are so well known that it is not necessary to indicate their geographical location, in which case the County column is blank.

UK Postcodes and Post Towns
PostcodeDerived FromCounty or RegionUsual Abbreviation
ALSt AlbansHertfordshireHerts
BDBradfordWest YorkshireW Yorks
BNBrightonEast SussexE Sussex
BTBelfastNorthern IrelandN Ireland
CVCoventryWest MidlandsW Midlands
DGDumfries & GallowayScottish Borders 
DLDarlingtonNorth YorkshireN Yorkshire
DNDoncasterSouth YorkshireS Yorkshire
DYDudleyWest MidlandsW Midlands
EEast LondonLondon 
ECEast Central LondonLondon 
FYFylde CoastLancashireLancs
GYGuernseyChannel Islands (includes Alderney and Sark)CI (see note)
HDHuddersfieldEast YorkshireE Yorks
HGHarrogateNorth YorkshireN Yorks
HPHemel HempsteadHertfordshireHerts
HSHebridesWestern Isles 
HUHull (officially: Kingston-upon-Hull)East Yorkshire 
HXHalifaxWest YorkshireW Yorks
IMIsle Of ManLancashireIOM (see note)
JEJerseyChannel IslandsCI (see note)
KWKirkwallOrkney IslandsOrkneys
LDLlandrindod WellsMid Wales 
LSLeedsWest YorkshireW Yorkshire
MKMilton KeynesBuckinghamshireBucks
NNorth London  
NENewcastle Upon Tyne  
NWNorthwest London  
SESoutheast London  
SRSunderlandTyne & Wear 
SWSouthwest London  
TDTweedsdaleScottish BordersBorders
WWest London  
WCWest Central London  
WFWakefieldWest YorkshireW Yorks
WSWalsallWest MidlandsW Midlands
WVWolverhamptonWest MidlandsW Midlands
ZEZetland (Shetlands)Shetland Isles 

Note: The Channel Islands (CI), together with the Isle of Man (IOM), have their own postal authorities. The rules regarding undeliverable UK mail without a return address described below do not apply to these authorities because their mail is returned to them for disposal, as they are regarded as independent mail authorities, despite the fact that they are part of the United Kingdom.

Q. When can the Royal Mail pulp my mail?
A. When it is discounted UK postage, is undeliverable for whatever reason, and doesn't have a return address.
Q. What does 'discounted' mean?
A. Discounted mail is mail that is handled for less than the normal rate, such as metered mail (franking machines), PPI, and Mailsort.
Q. What happens to undeliverable non-discounted mail?
A. Non-discounted mail, such as normal stamps, Smartstamps, and Horizon (the sticky white label you get at many UK post offices) is treated as follows: if there is a return address on the outside, the item is returned. If not, the item is sent to a specially vetted unit where it is opened. If the address of the sender can be identified, the item is returned. If not, any valuables become the property of the Treasury and the rest is destroyed.
Q. What difference does an outward postcode make?
A. It means that your letter will not be intercepted and killed off by a Mail Centre, and will therefore reach an LDO. Think of Mail Centres as lymph glands that block and destroy stuff they don't like. LDOs (Local Delivery Offices) are the good guys. Getting past the Mail Centre is what your letter needs to do, and the Outward Postcode will ensure that. The good guys (LDOs) will do the rest. They are the people who know their local communities.
Q. What is meant by "killed off".
A. "Killing off" a mail item means bringing down a big rubber stamp on it, or applying a sticker, which means it is no longer a "live" item. What happens to it after that depends on the various rules we explained earlier: foreign, discounted or non-discounted, return address or no return address. Mail with foreign postage is returned to the country of origin (and this includes the Channel Isles and Isle of Man). Our best advice to everyone posting mail to the UK or from within the UK is: ALWAYS USE A RETURN ADDRESS!
Q. Why is using a return address so important?
A. Because if an undeliverable item is posted using a discounted service, a return address means you'll get your letter back. If you don't have a return address, and your letter was discounted, the Royal Mail will destroy it, and you'll never know what happened to it. If you include a return address and your letter was never returned, you'll know it was delivered. Without a return address, if it's undeliverable discounted UK mail, you will be forever in the dark.
Q. Glasgow has lots of postcodes. Why do you list only one in the Postcode Finder?
A. Like all the major cities in the UK, Glasgow has many areas. Each area has its own individual postcode. If you know the postcode for that area, then use it. But what do you do when you only know the name of the street? Simple! Use the postcode for the centre of the city! Your item will reach the city centre's LDO. Remember what you read about Mail Centres and LDOs? The bad guys and the good guys? But don't just guess because you will soon be found out. If you know the area of a certain city, such as Aston (Birmingham) or Anniesland (Glasgow), then you will get an accurate postcode from the Listmasters Postcode finder.
Q. Why did my postcard get to my cousin a month after I returned from holiday?
A. Probably because you didn't put a postcode on it. Postcards, birthday cards, and Christmas cards are often impulse mailings, and you may not have your address book with you at the time. Always carry your address book! Address all your mail correctly. And another piece of advice regarding Christmas cards and birthday cards - yes, you've guessed it! Include a return address.
Q. I sent some holiday photo snaps to a relative. They never arrived. Why not?
A. Sending a few photos in an envelope might not seem to be a problem. But remember, postal systems are getting highly mechanised all the time. Five or six photos in an envelope will jam the machines and tear the envelope to shreds, spreading the photos all over the place. In other words, your holiday snaps are lost forever. It's much better to put a bunch of photos in a Jiffy bag because Jiffy bags are treated as packets and so avoid the machines.
Q. I regularly send letters to my nephew in Bangladesh. He replies but it is apparent that some replies are not getting through to me here in the UK. Why is that?
A. Your nephew is trying to copy your English address in a script he is not familiar with. Sometimes it comes out right, and sometimes not. The solution is to print some labels of your address in English and send them to him. When he wants to write to you, he writes in Bangla and sticks one of your labels on the outside of the envelope. Simple solution!
Q. I sent some Christmas presents to my relatives in Canada but they never arrived, and I didn't get them back. Why not?
A. Canada has recently introduced a policy of rejecting any packets which do not have a return address printed on the outside. They won't even try to deliver the item. Since the presents had no return address on the outside, the Royal Mail had no option but to open them and then destroy them because there was no clue inside as to the identity of the sender.

Address Databases

Database designers are too inflexible in their approach, designing databases to cater for addresses in their own national format. When a US or UK address is input, it may look acceptable on the screen, but when it comes to printing labels or envelopes, the result is often an unintelligible. The solution is to have a free form address block without any verification, trusting the input operator to type exactly what is in front of him/her.

PO Box Numbers

Many people think that UK PO Box numbers are unique. Not so! Any PO Box number can be assigned to hundreds of firms throughout the UK. It only becomes unique to one particular company when it is used in conjunction with a Postcode. A PO Box number always comes with a postcode, and it is essential that you use it.

To Conclude

Everyone should now have a better understanding of how the UK postcode system works, which was one of the reasons why this website was conceived in the first place by ex-Royal Mail staff. Always use original source documents for addresses whenever possible: business cards, invoices, etc, and make sure your address database is flexible enough to handle addresses in peculiarities of the UK postcode system. Your database manager should be held accountable for this. Remember, your image or the image of your company, is reflected in the way it is able to communicate, and if your correspondence takes weeks instead of days to reach its destination - or even worse, doesn't arrive at all because of a bad or garbled address - it will not reflect favourably on you or your company, and its ability to do international business. It's a global market and if you want to succeed, you have to think globally.