This address validation glossary defines the essential terms behind UK address data and quality — including Royal Mail PAF (the official record of around 31 million deliverable addresses across roughly 1.8 million postcodes), UPRN, UDPRN, delivery points and postcodes. Use it as the single reference node that links to every definition on the site.
A–Z of address validation terms
Address autocomplete
A form feature that suggests real addresses from PAF as a user types, so they select rather than type the full address.
Address validation
Checking that an address is real, deliverable and correctly formatted against an authoritative dataset such as Royal Mail PAF.
Address verification
Confirming that an address genuinely exists and can receive mail by matching it against Royal Mail PAF.
BFPO
British Forces Post Office addresses used for serving military personnel, handled outside the standard postcode structure.
Delivery point
A single address that can receive mail. There are around 31 million delivery points recorded in Royal Mail PAF.
PAF
Royal Mail's Postcode Address File — the official database of every deliverable UK address and postcode.
Postcode
A 5–7 character alphanumeric code identifying a small group of addresses. The UK has roughly 1.8 million postcodes.
UDPRN
Unique Delivery Point Reference Number — an 8-digit identifier Royal Mail assigns to each delivery point in PAF.
UPRN
Unique Property Reference Number — a persistent identifier assigned to every addressable location in Great Britain.
Why does this terminology matter?
Getting the terms right helps you choose the correct tool for the job. If you need to confirm an address exists, that's verification; unique property identifiers come from UPRN and UDPRN; and everything ultimately traces back to Royal Mail PAF data.
A modern, UK-first alternative
AutoPostcode is a developer-friendly, affordable alternative to Loqate, Fetchify and Ideal Postcodes — the same Royal Mail PAF data, a faster integration and clearer pricing.
Frequently asked questions
What is an address validation glossary?
It's a reference of the key terms used in UK address data and validation — such as PAF, UPRN, UDPRN, delivery point and postcode — each defined in plain English with links to fuller explanations.
What is the difference between UPRN and UDPRN?
A UPRN (Unique Property Reference Number) identifies an addressable property across Great Britain, while a UDPRN (Unique Delivery Point Reference Number) is an 8-digit Royal Mail identifier for a delivery point in PAF.
What is Royal Mail PAF?
PAF is the Postcode Address File — Royal Mail's official database of around 31 million deliverable UK addresses across roughly 1.8 million postcodes, and the authoritative source for validation.
What is a delivery point?
A delivery point is a single address that can receive mail. Royal Mail PAF records about 31 million of them across the UK.
How many UK postcodes are there?
There are roughly 1.8 million live postcodes in the UK, each covering a small group of addresses, all recorded in Royal Mail PAF.
Where can I learn more about each term?
Every term in this glossary links to a dedicated explainer, and the whole set is powered by the same PAF data behind the AutoPostcode API.
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