CAF (Corporate Address File) consists of an API that exposes a web service using SOAP in order to request address data from the CAF database.

The CAF API requires a client to provide an API key upon each request. If the API key provided does not match one of those distributed then the call will fail.

The API documentation can be accessed here.

General CAF Concepts

Address Validation Unit (AVU)

The AVU is the person, group, or organisation whom maintains the CAF database.


Each new address or new revision of an existing address in the CAF will receive a sequentially assigned CAF ID. The CAF ID therefore represents the state of the CAF immediately after that update was accepted.

When an address is revised, a new CAF ID is allocated for the revision and this CAF ID becomes the successor of the previous version. CAF IDs may be merged in which case two CAF IDs will have the same successor.
Client databases will store CAF IDs in their local tables to represent addresses. When an address is updated, the client database will receive a new CAF ID and the new address fields to replace the details on record.

Delivery Point ID

A delivery point ID is a unique number to identify an address. The delivery point ID does not change from one version of an address to another. API calls are provided to retrieve addresses by delivery point ID, which means the delivery point ID can be used by systems instead of the CAF ID in order to store the link to a CAF address.

Candidate and Accepted Addresses

A ‘candidate’ address is an address which has been submitted by a client to the CAF. It may be a new address or a proposed amendment to an existing address. In the latter case, the client will specify what address is being amended. Candidate addresses will subsequently be accepted or discarded by the AVU. If a candidate is accepted, a new ‘accepted’ address is created, with a further new CAF ID created to represent it.

Current Address

The ‘current’ address for a given CAF ID is the last accepted address reached by following the chain of successors starting from that CAF ID.

Address Succession

Internally the CAF tracks addresses using links between CAF IDs:

  • Each address (either candidate or accepted) has a link to its successor. New candidates and current addresses to not have successors.
  • Each candidate address also has a link to its predecessor only if it is a proposed update as opposed to a new address.

A CAF address lifecycle is illustrated in the following diagram which demonstrates various update scenarios.