What is PAF and how does it work?

26th September 2016

If you have used a mailing house in the past to send out a direct mail campaign using names and addresses from a data file, you may have heard of PAF, especially connected with Royal Mail; but what is PAF and why should you use it?

PAF stands for Postal Address File. It is a collection of valid UK postal addresses created and maintained by Royal Mail. Each address on PAF consists of several parts, such as the town, county, and postcode. Combining these address parts in the correct order reveals what Royal Mail consider the PAF valid address.

Data Cleaning

The accuracy of your mailing list data will vary depending on its source.

Inaccurate data may include addresses that are incorrect (missing a postcode, wrong house number, incorrectly spelt town), in these instances, the mail may not reach the intended destination.

Mailing data can be cleaned using PAF correction software. Various parts of the original address, such as the postcode, town, or premise, are used to find a match in the PAF collection. If a matching address can be found, the original address can be replaced with the PAF valid version resulting in a cleaner data file. Whether a match can be found depends on the original address and the accuracy of the matching software.

Some mailing houses offer manual PAF correction, where a person will look up addresses that cannot be matched automatically and use their judgement to find and correct the invalid address.

Often, addresses may not be considered PAF valid because of simple spelling errors, or perhaps somebody has named their house and they do not refer to it using the official building number. In these cases, the mail will reach its intended destination and the data does not need correcting.

Sorting Mail for Postage Discounts

When you use a postal provider to send a printed campaign of a qualifying size, you have the option to sort your mailing by area and then bag up the mail in particular order. This will earn you a discount on your postage cost as sorted mail can be delivered directly to the correct distribution centre without the postal provider having to examine each piece of mail individually.

There are many sort options available and the content of your campaign and the number of mail items determines which options are available to you. In order to qualify for discounts, the postal provider has to be certain that the addresses you have supplied are valid, and they do this using PAF.


Each address on PAF has a Delivery Point Suffix, or DPS. The DPS is a combination of a single number and a single character, e.g. 1D.

In combination with the postcode, the DPS identifies a unique address within the UK. Mailing files can be matched against PAF in order to find their DPS without having to replace the original address information. If an address cannot be matched against PAF, it is given a default DPS of 9Z flagging it as unidentified.

Mailing files must have a minimum percentage of addresses with an identified DPS to qualify for discounted services. The required match level varies depending on the type of service required.


PAF allows you to improve your mailing data with accurate addressing which in turn allows access to discounts with postal providers. However, it is important to remember that PAF is a licensed product that is owned by Royal Mail who charge data processing bureaus a fee to have access to and use the data, a cost that will be passed onto the end-user.