Everything You Need to Know About Royal Mail PAF

The Royal Mail Postcode Address File — almost always shortened to PAF — is the authoritative database of postal addresses in the United Kingdom. It contains the addresses of over 30 million properties, and it is the single source of truth that quietly powers everything from your morning parcel delivery to the postcode lookup box in an online checkout.

If you build software, run an e-commerce store, manage a delivery operation or simply want to understand how UK addresses actually work, this is the complete guide. We cover what PAF is, what's inside it, the history of the postcode, how PAF is used today, how to access it, and how a modern API like AutoPostcode turns raw PAF data into a fast, reliable address experience.

What is the Royal Mail PAF?

PAF stands for Postcode Address File. It is a comprehensive, regularly updated database containing the postal addresses of more than 30 million properties across the United Kingdom, owned and maintained by Royal Mail Group Ltd, which also holds the copyright in the data.

Today, PAF is what ensures mail and parcels get delivered to the right door, and it keeps commerce moving through postcode lookup and address verification services. When you type a postcode into a checkout and a list of addresses appears, that list is coming — directly or indirectly — from PAF.

Here's what the PAF database broadly contains:

• 30 million+ UK postal delivery addresses
• Around 1.8 million UK postcodes
• Millions of UK business (organisation) records
• Several thousand addresses for British service personnel overseas (BFPO)

Organisations and developers can access the PAF database — connecting their software to it so they can return accurate addresses and postcodes. Postcode lookup in e-commerce checkouts, address verification in CRM systems, and route planning in logistics are all powered by PAF.

A brief history of the postcode

To understand PAF, it helps to understand where the postcode came from. The story stretches back much further than most people assume.

Flash back to the 1850s: Royal Mail was overwhelmed by surging mail volumes driven by population growth. Back then postcodes didn't exist, so mail carriers navigated using street names and literally counted houses as they walked their rounds. It worked, but it didn't scale.

In the mid-1850s, London — which received the bulk of the country's mail — was divided into postal districts (EC, WC, N, E, SE, SW, W, NW), and properties were given a code. The rest of the country gradually adopted the system, with the roll-out finally completed in 1934.

The modern postcode we recognise today was created in 1959 and trialled in Norwich under Postmaster General Ernest Marples. By 1974, every property in the UK had its own postcode, uniquely identifying it from every other address in the country.

The creation of PAF

Before computers and databases, Royal Mail kept paper records of postal addresses that organisations could buy. Paper records took up enormous space and were painfully slow to maintain, so the arrival of affordable electronic storage in the 1980s was a turning point.

In the early 1980s, Royal Mail built the first electronic database of postal addresses. While the database itself was digital, data collection was still paper-based — post carriers wrote down address changes and submitted them manually. The process was slow and infrequent, but it was a remarkable improvement on what came before.

By 1992, the manual, paper-based entry system was replaced by a digital maintenance solution with real-time updates. To put the scale of change in perspective: in 1992 PAF received roughly 200–600 updates per day. Today it receives 4,000–5,000 updates every working day, leaving no address unturned when changes are needed — new builds, demolitions, renamed streets and reclassified premises all flow into the file continuously.

What data is in PAF?

The PAF database holds structured address details, broken down into recognisable components:

• Premises — building names, building numbers, sub-building (flat / unit) details and PO Boxes
• Thoroughfares — street and road names
• Localities — dependent and double-dependent localities, plus the post town
• Postcode — the full outward and inward code that ties it all together

PAF records three categories of delivery point: Small User Residential, Small User Organisation and Large User Organisation. Coverage spans Great Britain and Northern Ireland, excluding the Republic of Ireland and a small number of delivery points such as certain churches and substations.

How PAF is used today

Royal Mail owns and maintains PAF and makes the data available to external organisations as raw data. While its original purpose is delivering mail, PAF's reach now extends across almost every sector that touches a UK address.

It is used by nearly every delivery company in the United Kingdom, making it integral to the logistics sector. Beyond delivery, PAF underpins satellite navigation, mapping, geocoding and customer-profiling services — and it runs deep through supply chains. E-commerce websites use it to provide postcode lookup, warehouses use it to verify shipping addresses, and credit-check companies use it to confirm the identity of new customers.

The simplest everyday example is postcode lookup in e-commerce. When you type a postcode into a lookup field and a list of matching addresses appears, that accuracy comes from PAF. Royal Mail estimates that over 40,000 businesses use PAF to:

• Develop address lookup and verification software
• Make online transactions faster and easier
• Deliver mail and parcels efficiently
• Verify customer information at the point of capture
• Manage and clean shipping databases
• Identify and group addresses within geographic areas

The use cases are effectively limitless. PAF plays a crucial role in any technology that needs accurate, up-to-date information on UK addresses.

How AutoPostcode uses PAF

Our postcode lookup API is built directly on PAF, so it finds verified delivery addresses in seconds. We offer two complementary solutions:

• Postcode Lookup — a user enters a postcode and instantly selects their full address from a list of PAF-verified matches.
• Address Auto-Complete — addresses are suggested as the user types, reducing keystrokes and eliminating typos before they happen.

PAF is integral to the service because it provides the database from which addresses are matched to postcodes. By using AutoPostcode you tap into PAF-verified data and integrate a reliable postcode lookup tool into your store or application — without licensing, hosting and continuously updating 30 million records yourself.

What problems does PAF solve?

PAF underpins databases with accurate postal delivery address information. Because it's automatically updated, trusted by tens of thousands of organisations, and sits behind thousands of third-party products, it solves a recurring set of business problems:

• Saves money by reducing the cost of returned and undelivered mail
• Saves time — it integrates cleanly into existing software
• Provides access to all UK postal addresses in a single source
• Verifies addresses in seconds at the point of entry
• Makes online transactions and checkouts faster
• Keeps databases, mailing lists and CRM systems up to date
• Reduces abandoned carts with fast postcode and address lookup
• Helps qualify for Royal Mail mailing discounts that require clean, validated data

When should you use PAF?

Now that you know how PAF is used, here are the business scenarios where reaching for PAF data — directly or via an API — makes the most sense:

1. You want to create or maintain a customer database that automatically keeps address and postcode information current.
2. You capture address details online but the submitted information is often fragmented — for example, only a postcode or a partial address.
3. You rely on accurate address and postcode data for mailing lists, sales, marketing and promotional activity.
4. You're a delivery company that wants to keep addressing in-house, with full control over the data rather than being tied to a single service.
5. You want to build a rapid addressing system or address auto-fill tool for internal teams or external customers.

In short, use PAF to create, manage and maintain customer databases, mailing lists and CRM systems. The delivery address and postcode records inside PAF can form the backbone of almost any address-aware database.

How to access PAF data

There are two main routes to PAF, depending on your needs and your appetite for infrastructure:

1. License the raw data from Royal Mail

You can license the full PAF dataset directly from Royal Mail. This gives you the underlying file, but it also means you're responsible for hosting it, building lookup logic, applying frequent updates and staying within the licensing terms. It suits large organisations with dedicated data teams and very high volumes.

2. Use a PAF-backed API

For most businesses, an API is the faster, cheaper and far simpler path. A service like AutoPostcode handles the licensing, hosting and continuous updates for you, exposing PAF through a clean API and ready-made plugins. You get accurate, current addresses without operating the database yourself — and you only pay for the lookups you use.

Frequently asked questions

What is Royal Mail PAF?

PAF is Royal Mail's official Postcode Address File — the master database of UK postal addresses, containing over 30 million delivery addresses, around 1.8 million postcodes and millions of business records.

How many addresses does PAF contain?

More than 30 million UK properties, plus several thousand BFPO addresses for service personnel overseas. It's updated thousands of times every working day.

Is PAF the same as postcode lookup?

No. PAF is the underlying address database; postcode lookup is a service built on top of it that lets someone type a postcode and instantly select their verified address.

How do I get started with PAF data?

The quickest way is through a PAF-backed API. With AutoPostcode you can create an account, grab an API key, and add PAF-verified postcode lookup to your website or app in minutes.