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Postcodes and postal service change of address explained

Postcodes & Addresses Explained

Frequently Asked Questions

Postcodes were introduced by Royal Mail as a quick and accurate way of identifying a group of addresses.

Click on one of these links to find out more:

  1. What is a postcode?

    A postcode is made up of a combination of letters and numbers in one of the following ways:

    • A1 2BC
    • D34 5EF
    • GH6 7IJ
    • KL8M 9NO

    The same code is usually used for a small group of addresses so is not unique to every address but helps to pin-point exactly where the item of mail needs to go to.

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  2. How does a postcode work?

    Each part of the postcode provides step-by-step information about where the item of mail is heading. From left to right the postcode narrows down its destination.


    EC 1V 9 HQ
    The first one or two letters is the postcode area and it identifies the main Royal Mail sorting office which will process the mail. In this case EC would go to the Mount Pleasant sorting office in London. The second part is usually just one or two numbers but for some parts of London it can be a number and a letter. This is the postcode district and tells the sorting office which delivery office the mail should go to. This third part is the sector and is usually just one number. This tells the delivery office which local area or neighbourhood the mail should go to. The final part of the postcode is the unit code which is always two letters. This identifies a group
    of up to 80 addresses and tells the delivery office which postal route (or walk) will deliver the item.
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  3. Why do I need to use the postcode?
    Using the postcode means that the majority of mail can go through our automated sort machines allowing it to be sorted quickly and accurately.
    If mail does not have a postcode or has an incorrect postcode it will have to be sorted manually which takes longer and can mean that mail is sent to the wrong destination (although most mail is still delivered correctly and on time).
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  4. I’m moving, why can’t I keep the same postcode?
    In general, a postcode identifies a group of up to 80 addresses. So if your business is moving to larger premises next door then you may well have the same postcode, but if you are moving house to another town then your postcode will change. The postcode is specific to the address not to you or your business unless you have a unique large-user postcode.
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  5. What is a unique large-user postcode and how do I get one?
    Some organisations who receive large volumes of mail can have unique postcodes to ensure that mail to an individual address is correctly segregated. If you receive at least 500 items of mail a day you may be eligible for a unique large user Postcode. Contact us for more information.
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  6. Why can’t I have the same postcode as the previous organisation at this address?
    This can occur if the previous occupant had a unique large-user postcode. A new business moving to this address will either use the standard postcode for that address or have their own unique large-user postcode.
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  7. Why is Royal Mail changing my postcode/address?

    We are committed to a policy of not changing addresses or postcodes wherever possible. We will only make changes to benefit the service we give to you, or when it is absolutely necessary, for example:

    • A new Royal Mail delivery office is opened
    • We have run out of postcodes for new homes and businesses in a developing area
    • The local council has prompted a change by re-numbering buildings or re-naming roads

    We will always write to you to tell you about any changes we plan to make. For about 12 months from the time that we notify you of any changes, our sorting machines will recognise both your old and new postcodes. This should give you ample time to use up stocks of stationery and notify your customers, friends and relations of the change, although we recommend that you switch to your new postcode as soon as possible.

    For more information about why we change postcodes and addresses you can download our Code of Practice.  This has been produced in conjunction with Consumer Focus, the independent consumer council for postal services (formerly Postwatch).

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  8. Where can I get maps showing postcode areas?
    Royal Mail doesn’t produce such maps, but there are a number of companies who do provide maps of address and postcode information. Try using the 'keyword search' to find such companies in our Supplier Directory.
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  9. How do I go about changing the name of my house or office building?

    We do not name or number properties or streets. This is the responsibility of the naming and numbering authority (usually called the Highways or Engineers Department) at your local council. You’ll need to make your request to them in writing along with a few alternatives in case your first choice already exists.

    If your property is officially numbered you can’t swap the number for a name but you can use a name in addition to the number.

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  10. What is a correct Postal Address?

    Every house and business in the UK has a complete postal address that helps Royal Mail deliver mail quickly, accurately and cost effectively.
    We’ve laid out below the elements that make up a postal address and those that are required for us to deliver mail.

    Address Is it Required? Information
    Mr A Smith When applicable Addressees Name
    Acme Plc When applicable Company/Organisation
    Acme House Yes (except if it has a number) Building Name
    3 High Street Yes Number of building and name of thoroughfare
    Hedle End Yes but only if a similar road name exists within a Post Town area Locality Name
    SOUTHAMPTON Yes Post Town please print in capitals
    SO31 4NG Yes Postcode please print in capitals

     You do not need to include a County name provided the Post Town and Postcode are used.

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  11. Why isn't my address appearing?

    There are several reasons why addresses don't appear and we've listed a few of the common ones below. If they apply to you, please email the correct information to: with all details, so we can make sure your address appears.

    Spelling - if it's the name of your house that we have spelt incorrectly, you can email us to correct this. If it is a road, village or town name we would keep the spelling your local council have confirmed to us. 

    Brand new houses - Local Councils confirm the addresses of newly built or re-developed properties to us months before you move in.  But we don't make properties live on our PAF system until someone lets us know that an individual property can receive mail. If you've just moved in, please email us to let us know and we'll make your new address live.    

    Just not there! - for whatever reason, it might be just that we haven't recorded your address on our database. Please let us know where you live.

    The email address to let us know the correct information is:

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  12. Why won't companies deliver goods to my house?
    Many mail or online shopping organisations won't deliver to business addresses.  So it might be that we have your house listed as a 'business' rather than a 'residential' address. To amend this, please email
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