Open Projects

Building-Level Postcodes: A Full Address from a Postcode and a Door Number

Summary

In many countries a postcode covers a whole district or neighborhood, so addresses are typed as long free text and are often wrong or incomplete. This proposal gives each building (or a small group of buildings) its own unique postcode, as in the UK system. Then a postcode plus a door number is enough to find the full address. Forms can validate and autofill addresses, and the costly work of correcting bad addresses, which today supports a whole industry, is largely no longer needed.

Problem

When a postcode covers a large area, it cannot identify a specific address. People have to type the street, building name, number, neighborhood and district as free text.
Free-text addresses are written in many different ways: spelling mistakes, abbreviations, missing parts, old street names. The same building can appear in dozens of forms.
Because addresses cannot be validated at the moment they are entered, errors are discovered only later, when a parcel does not arrive, a bill goes to the wrong place or a service cannot find the house.
Significant effort and money go into fixing these errors afterwards. Companies are set up just to clean and correct address data, and organizations run large address-correction projects. All of this is a waste caused by a missing system.
In emergencies, an unclear address costs time exactly when time matters most.

Two address forms side by side: today, a long free-text address box with errors and many possible matches; with building-level postcodes, a postcode and door number instantly fill in one verified full address

Proposed Solution

Introduce a detailed postcode system in which the postcode points to a building, not to a whole area:

One postcode per building: each building, or a small group of neighboring buildings, gets a unique postcode. Postcodes stay regionally meaningful: the first part shows the wider area, the last part narrows it down to the building.
Postcode plus door number is enough: from these two pieces of information, the full official address can be found without typing anything else.
One public address reference: the postcode authority maintains an official list that links each postcode to its buildings and full addresses, kept up to date as buildings are added, renamed or demolished.
Validation and autofill everywhere: public services, online shops, banks, couriers and utilities can check the address when it is entered and fill it in automatically, so errors are caught at the start.
Free text becomes the exception: free-text entry remains only for rare cases, not as the default.

How It Works

Step	Today (area-level postcode)	With building-level postcodes
Entering an address	Type the full address as free text	Enter postcode and door number
Checking it	Not possible at entry	Checked instantly against the official list
Result	Many spellings for the same place	One standard, verified address
Fixing errors	After delivery fails, often by specialist firms	Rarely needed
Emergency response	Time lost interpreting the address	Building identified directly

flowchart TD
    Enter(["User enters postcode"]) --> Lookup["Official list returns the buildings for this postcode"]
    Lookup --> Door["User enters or picks the door number"]
    Door --> Found{"Address found?"}
    Found -->|Yes| Fill["Full address filled in automatically and verified"]
    Found -->|No| Check["User is asked to check, or reports a missing address to the postcode authority"]
    Fill --> Use["Used by shops, couriers, public services and emergency response"]

Implementation & Phasing

Design and official address reference: the national postcode authority, with municipalities and the land registry, designs the building-level scheme and builds the official list linking postcodes to buildings and addresses.
Pilot region: assign building-level postcodes in one city or region and test them with public services, couriers and online shops.
Nationwide rollout: extend the scheme region by region. Old postcodes remain accepted during a transition period.
Adoption across services: public forms and major private services switch to postcode plus door number entry with validation and autofill.
Continuous maintenance: new buildings get a postcode as part of the building permit and address assignment process, so the list stays current.

Stakeholders & Benefits

Citizens: faster, easier forms and fewer lost deliveries and misdirected letters.
E-commerce and logistics companies: fewer failed deliveries and less money spent on cleaning address data.
Postal service and couriers: clearer routing down to the building.
Public services and utilities: accurate records for billing, notices and service delivery.
Emergency services: quicker, more reliable identification of where help is needed.
The wider economy: resources now spent on correcting addresses can go to productive work, supporting digital government.

Risks & Mitigations

Risk	Mitigation
People and businesses have to learn new postcodes	Transition period where old postcodes still work; postcodes shown on building plates and official documents
The official list becomes out of date	Postcode assignment tied to building permits and address changes; easy reporting of missing addresses
Cost of redesigning the postcode system	Pilot region first, then phased rollout
Rural or scattered buildings are hard to group	Flexible rule: one building or a small group, decided locally
Some services keep using free text	Public services lead the change; validation offered openly so private services can adopt it easily

Keywords: postcode, postal code, address validation, address autofill, digital government, e-commerce, logistics, emergency response, address data quality

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Origin

Originally proposed by Merih İlgör (June 2025); published here as an open project idea.

License

This work is licensed under CC BY-NC-SA 4.0 for non-commercial use; see LICENSE. Commercial use requires a revenue-share agreement; see COMMERCIAL-LICENSE.md. Modified versions may not be sold or transferred to third parties as new ideas, and patent-like rights are reserved; see COMMERCIAL-LICENSE.md.