Address validation is the process of confirming that a postal address is real, deliverable and correctly formatted by matching it against an authoritative reference dataset. In the UK that dataset is Royal Mail's Postcode Address File (PAF), which contains around 31 million deliverable addresses across roughly 1.8 million postcodes. When you validate at the point of entry, only genuine, standardised UK addresses are ever saved.
What does address validation actually check?
Address validation checks that the address exists in Royal Mail PAF, is a live delivery point, and is formatted to the correct standard. It catches typos, missing house numbers and wrong postcodes before they become permanent bad records.
- The postcode exists and is live in PAF
- The premises (building name/number) matches a real delivery point
- The thoroughfare, locality and post town are correct
- The address is standardised to Royal Mail formatting
How does address validation work?
A user enters a postcode or partial address and the system queries Royal Mail PAF in real time. Matching addresses are returned for selection, then standardised and confirmed as deliverable. Because the match happens against ~31M authoritative records, the saved address is guaranteed to be real. See it in action with our UK address validation API.
Validation vs verification vs autocomplete
| Term | What it does | When |
|---|---|---|
| Address validation | Confirms format & deliverability | On submit / at capture |
| Address verification | Confirms the address exists in PAF | On submit / batch |
| Address autocomplete | Suggests real addresses as you type | During entry |
These overlap heavily. Read our companion definitions of address verification and how full UK address verification combines both in one lookup.
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 address validation?
Address validation is the process of checking that an address exists, is deliverable and is correctly formatted by matching it against an authoritative reference dataset — in the UK, Royal Mail's Postcode Address File (PAF), which holds around 31 million addresses across 1.8 million postcodes.
What is the difference between address validation and verification?
Address validation confirms the address is structurally correct and formatted to PAF standard; address verification confirms the address genuinely exists and is deliverable. In practice AutoPostcode does both in a single PAF lookup.
How does address validation work?
A user's input (usually a postcode or partial address) is matched against Royal Mail PAF. Matching records are returned, standardised to the correct format and confirmed as deliverable delivery points before the address is saved.
Why is address validation important for ecommerce?
Unvalidated addresses cause failed deliveries, refunds and support tickets, each costing £10–£15. Validating at checkout means only real, complete UK addresses ever enter your system.
Does address validation use Royal Mail PAF?
Yes. AutoPostcode validates every UK address against Royal Mail PAF — the official record of ~31M deliverable addresses — so results are authoritative and continuously updated.
Can I validate addresses in bulk?
Yes. As well as real-time checkout validation, you can batch-cleanse existing records against PAF to correct, standardise and de-duplicate historic addresses.
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