Postcodes
How Postcodes Are Assigned
National postal operators or governments assign postcodes based on delivery routes and address density. Learn how the process generally works.
Updated 14 October 2026 · 2 min read
Postcodes are assigned by the national postal operator or by a government body responsible for postal services. Residents and businesses do not choose their own code. It is determined by where the address sits in the delivery network.
Starting from delivery routes
The practical building block is the delivery route. Operators group addresses into rounds that a carrier can cover in a shift, then align postcodes with those groups. This is why codes often follow streets and rounds rather than neat administrative boundaries, and why a code can cross a town or district border.
Hierarchy first, detail second
Designers usually start with the broad levels, dividing the country into regions and sorting areas, and then subdivide into districts and delivery zones. The structure follows the sorting flow described in how mail sorting uses postcodes. Fine detail is added as needed, for example where a street is long or a building receives large volumes of mail.
Different densities, different sizes
A dense city may need many small codes to keep rounds manageable, while a sparse rural area can be covered by one code over a large span. The size therefore varies a lot; see how big is a postcode area.
New streets and buildings
When new roads or developments appear, the operator assigns or extends codes once the addresses are registered. This can take time, which explains delays in postcodes for new-build homes.
Special cases
Some receivers get a code of their own because of the mail they handle, as explained in postcodes for large organisations. PO boxes also receive codes, covered in postcodes for PO boxes.
No global authority
There is no worldwide body issuing postcodes. Each country sets its own rules, so formats and practices differ. Some countries have no nationwide system at all; see countries without a postcode system.
An exact-location code from UPCS is not assigned this way. It is generated from map coordinates, it is not an official postal code, and it does not replace the code assigned by your national postal operator.
Frequently asked questions
Who assigns postcodes?
In most countries the national postal operator or a government body assigns and manages postcodes.
Can I choose my own postcode?
No. A postcode is assigned to an area or delivery point by the postal authority and cannot be chosen by residents.