The Australia Post tracking number format is usually comprised of 2 alphabetic characters, 9 numeric characters, and end with 2 alphabetic characters, "AU". 

Australia Post tracking number format:

2 letters + 9 digits + AU

Australia Post, also a government-owned corporation, is founded in 1809. It has been keeping Australia connected for more than 200 years by delivering mail, helping businesses and consumers with parcels, and providing a national retail network that supports local communities and organizations. 

You can also track your Australia Post tracking number on trackingmore.com