The An Post tracking number format is usually comprised of 2 alphabetic characters, 9 numeric characters, and 2 alphabetic characters.
An Post tracking number format:
2 letters + 9 digits + 2 letters
An Post tracking number example:
With a "Post" in its name, An Post, founded in 1984, is also a state-owned limited company. As one of Ireland's largest companies, it provides a "universal postal service" to all parts of the country as a member of the Universal Postal Union, including letter post, parcel service, deposit accounts, Swiftpost, an all-Ireland next-day delivery service, and EMS, the international express-mail service.
You can also track your An Post tracking number on trackingmore.com